ARTICLE

Emergence of Sentinel Node Biopsy in Breast Cancer as Standard-of-Care in Academic Comprehensive Cancer Centers

Stephen B. Edge, Joyce C. Niland, Michael A. Bookman, Richard L. Theriault, Rebecca Ottesen, Eva Lepisto, Jane C. Weeks

Affiliations of authors: S. B. Edge, Roswell Park Cancer Institute, Buffalo, NY; J. C. Niland, R. Ottesen, City of Hope National Medical Center, Duarte, CA; M. A. Bookman, Fox Chase Cancer Center, Philadelphia, PA; R. L. Theriault, M. D. Anderson Cancer Center, Houston, TX; E. Lepisto, National Comprehensive Cancer Network, Rockledge, PA; J. C. Weeks, Dana-Farber Cancer Institute, Boston, MA.

Correspondence to: Stephen B. Edge, MD, Roswell Park Cancer Institute, Elm and Carlton Sts., Buffalo, NY 14263 (e-mail: stephen.edge{at}roswellpark.org).


    ABSTRACT
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
Background: Ongoing clinical trials are addressing the accuracy and safety of sentinel node biopsy (SNB) in the treatment of breast cancer; however, SNB is already increasingly being used in clinical practice. This study examined the extent and time trends of the use of SNB in stage I and II breast cancer patients. Methods: Clinical data were collected from stage I and II (tumor size <=5.0 cm) breast cancer patients (n = 3003) who were treated at five comprehensive cancer centers between July 1, 1997, and December 31, 2000. Axillary surgery was classified as SNB alone, SNB + axillary node dissection (AND), AND alone, or none. Patterns of use of axillary surgery were summarized as the percentage of patients receiving each surgery type. The statistical significance of time trends for the use of SNB alone was analyzed by logistic regression models. All statistical tests were two-sided. Results: Overall, SNB alone was used in 13% of patients, SNB + AND in 22%, AND alone in 59%, and no axillary surgery in 6%. Use of SNB alone was statistically significantly associated with breast-conserving surgery of both smaller (<=2 cm) and larger tumors (2–5 cm) (P<.001 for both associations). For stage I cancer patients treated with breast-conserving surgery (n = 1763), use of SNB increased statistically significantly over the study period, from 8% in 1997 to 9%, 14%, 15%, 22%, 42%, and 58% for the next six consecutive 6-month time intervals, respectively. After controlling for center, age, and comorbidity, the odds ratio for the use of SNB alone was 2.30 (95% confidence interval = 1.88 to 2.82) for each 6-month interval (P<.001). Conclusions: Widespread use of SNB outside the clinical trial setting suggests that oncologists at cancer centers in our study have accepted SNB as standard-of-care for the treatment of breast cancer. This acceptance, if it occurs in other cancer centers and community practice, may affect accrual and generalizability of ongoing clinical trials of SNB.



    INTRODUCTION
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
Axillary lymph-node status is the most important prognostic factor for patients with breast cancer, and it affects the choice of adjuvant systemic therapy (1). Surgery to remove axillary lymph nodes for histopathologic examination is necessary to define axillary lymph-node status and remains an integral and potentially curative component of breast cancer care (2,3). Until recently, axillary node dissection (AND), which removes all the lymph nodes lateral to and beneath the pectoralis minor muscle (i.e., axillary levels I and II), was required to determine lymph-node status. Although this operation is safe, long-term sequelae are common, including upper arm paresthesias, shoulder and arm pain, restriction of shoulder mobility, and permanent and potentially disabling lymphedema (47).

The technique of sentinel node biopsy (SNB) may allow determination of lymph-node status without the use of AND (810). SNB is an attractive alternative to AND because the risks of short-term morbidity and lymphedema are markedly lower with this technique (1113). SNB involves injecting a colloidal material—most commonly technetium-labeled sulfur colloid and isosulfan blue dye—in the breast shortly before surgery. These colloids concentrate in the draining lymph nodes, termed sentinel nodes, which are identified at surgery and removed for pathologic examination.

The use of SNB is based on the premise that sentinel lymph nodes are the nodes at the greatest risk for cancer metastases and that, if these nodes are negative, the remaining axillary lymph nodes are also likely to be negative; hence, AND may not be necessary. Studies of SNB with concomitant AND have shown that the rate of false-negative SNBs is less than 5% in experienced hands, a level at which it may be acceptable to omit AND (9,10,14). However, a false-negative SNB may result in omission of needed adjuvant therapy, administration of inappropriate adjuvant therapy, avoidable axillary node recurrence, and, ultimately, an adverse effect on survival (1518). To address these issues, the National Cancer Institute (NCI) initiated two large-scale, cooperative-group clinical trials of SNB in 1999 (19,20). However, results from those trials will not be available until at least 2007.

Despite the absence of definitive clinical trial data, many physicians are using SNB in place of AND, and the use of SNB alone has been incorporated into national practice guidelines (2126). Defining the extent to which SNB has replaced AND as standard care for the treatment of breast cancer is difficult because there are no existing data sources that capture treatment information in sufficient detail. National registry programs, including the NCI Surveillance, Epidemiology, and End Results (SEER) Program1 and the National Cancer Data Base, have not collected surgical data in sufficient detail to define use of SNB. Indeed, even the use of administrative claims data may not identify SNB use patterns because SNB-specific procedure codes were not introduced until 1999.

A potential source of information on the use of SNB in specialty breast oncology practices is the National Comprehensive Cancer Network (NCCN) Breast Cancer Outcomes Project (2729), which was started by the NCCN in 1997. This project collects details on all biopsy and surgical operations for every patient treated at participating NCCN centers and provides a unique opportunity to examine the use of SNB at major cancer centers from 1997 through 2000, a time period when SNB was entering clinical practice in the United States. This article reports the patterns of axillary surgery use and time trends for the use of SNB as routine treatment for stage I and II breast cancer patients treated at five comprehensive cancer centers.


    PATIENTS AND METHODS
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
Study Cohort and Eligibility Criteria

The study cohort consisted of 3075 women who received their primary breast cancer care at one of the five original cancer centers participating in the NCCN Breast Cancer Outcomes Project since its inception in 1997: Dana-Farber Cancer Institute, Boston, MA; Roswell Park Cancer Institute, Buffalo, NY; Fox Chase Cancer Center, Philadelphia, PA; M. D. Anderson Cancer Center, Houston, TX; and City of Hope National Medical Center, Duarte, CA. Each center is an academic NCI-designated comprehensive cancer center, with breast clinical services provided by a limited number of full-time academic physicians. The majority of surgical and medical oncologists treating breast cancer at these centers devote most or all of their clinical effort to breast cancer care. The study, data abstraction process, data transmission methods, and storage protocols were all approved by the institutional review boards at each participating center. At centers where the institutional review board required signed informed consent for data abstraction, only data from patients who provided this consent were included in this analysis.

Women were eligible to participate in this study if they had newly diagnosed American Joint Committee on Cancer (AJCC) Stage Group I and II (30) (0–5 cm) invasive breast cancer and presented to one of the participating centers between July 1, 1997, and December 31, 2000. Patients with bilateral breast cancer or prior contralateral breast cancer and those who had received presurgical (i.e., neo-adjuvant) chemotherapy or radiation therapy were excluded from the study. To be evaluable in the analysis, patients were required to have complete follow-up information extending at least 90 days after initial presentation. Only surgical procedures performed before the date of last complete follow-up were included.

Data Sources

Data abstracted from medical records included sociodemographics, staging tests performed, tumor pathology, treatments administered [i.e., surgery, radiation, and systemic therapy (2729)], and tumor–node–metastasis (TNM) staging (30). The type of surgical procedure (e.g., lumpectomy, mastectomy, or axillary surgery) was recorded for all procedures, including those performed outside NCCN centers. Comorbidity at entry to the NCCN center was coded using either the Charlson Index (31) (based on chart review) or the modified version of that index using a patient survey developed by Katz et al. (32). Data from these indexes have been shown to be highly correlated (32). To optimize completeness of data abstraction and collection, each center chose the data abstraction technique (chart review or patient survey) that best fit the structure of its practice.

Classification of Axillary and Definitive Breast Surgery

Type of axillary surgery was classified into one of four categories for each patient: SNB without further axillary surgery (SNB); SNB followed by complete AND (SNB + AND); AND without sentinel node biopsy (AND); or no axillary surgery (None). Axillary surgery was coded as SNB alone if SNB was performed and the patient had no other axillary surgery at any time during initial treatment of the primary cancer. Axillary surgery was classified as AND alone if the surgical report showed axillary dissection and no prior or concomitant SNB. Axillary surgery was coded as SNB + AND if both SNB and AND were performed, whether on the same day or on different days. Axillary surgery was coded as "None" if the patient did not have any axillary node surgery.

Type of definitive breast surgery was classified as mastectomy, breast-conserving surgery, or no definitive breast surgery. Mastectomy included any procedure with removal of the entire breast (e.g., simple mastectomy, subcutaneous mastectomy, modified radical mastectomy, radical mastectomy, and all synonyms for these procedures). Breast-conserving surgery included all breast surgical procedures other than removal of the entire breast. The patient was categorized as lymph node–positive if any axillary lymph node contained metastatic disease (i.e., sentinel node or otherwise). During the time period studied in this analysis, the NCCN Outcomes Database did not separately record the pathology of sentinel and non-sentinel nodes; therefore, the rate of false-negative SNBs among patients with combined SNB + AND cannot be determined from these data.

Patients already participating in research studies involving SNB were also included in these analyses. Among the 3003 evaluable patients, only 48 were registered on such a protocol, and in no case did the protocol dictate the type of surgery the patient should receive. None of these patients were entered onto the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-32 trial in which women who are clinically lymph node–negative are randomly assigned to either SNB alone or SNB + AND. There were only three patients entered onto the American College of Surgeons Oncology Group (ACOSOG) Z0010 trial, in which women with a negative SNB do not have further axillary dissection. Of the other 45 patients registered on protocols involving SNB, six were on a single institutional IRB-approved training protocol and 39 were on a multicenter training and validation protocol in which SNB was performed without AND only after a surgeon had performed more than 25 cases combined with AND (33). Thirty-seven of the 45 (82%) patients received the combined techniques of SNB + AND. Because these protocols did not randomly assign patients to the type of axillary surgery used, these patients were included in our analyses. A separate analysis that excluded this small number of patients did not change the findings of this study (data not shown).

Patients who had some component of their surgery performed outside the NCCN center accounted for less than 10% of all patients. Because the NCCN center physicians who treated these patients had subsequent responsibility for their care and could have recommended additional surgery, these patients were also included in these analyses. Again, a separate analysis that excluded this small number of patients did not change the findings of this study (data not shown).

Statistical Analysis

Patterns of use of axillary surgery were summarized as the percentage of patients receiving each surgery type (i.e., SNB alone, SNB + AND, AND, or None). Statistical significance of time trends for the use of SNB alone was analyzed by logistic regression. The regression model for predicting use of SNB included the timing of definitive surgery, cancer center, comorbidity, and age as potential predictors. Whenever the time trend analysis encompassed more than one stage of breast cancer, stage was also included as a covariate.

Each logistic regression model was tested for goodness-of-fit using the Hosmer and Lemeshow test (34). The results of the goodness-of-fit tests were not statistically significant in all cases, indicating adequate fit of the models. Interaction terms were examined to accommodate varying increases in the use of SNB among the centers. Because a statistically significant interaction was found between the time trend for the use of SNB and center, the Cochran–Mantel–Haenszel chi-square statistic (35) was used to test for an association between categorical variables and axillary surgery; this analysis was also controlled for center.

Although the statistical testing was conducted via logistic regression, with time included as a continuous variable using the timing of surgery for each patient, for descriptive purposes, time trend data for axillary surgery type are shown in the tables and graphs as unweighted averages of the axillary surgery utilization proportions for the five centers over 6-month time periods. For each logistic regression model, we calculated the odds ratio for use of SNB, based on an unweighted average slope for time across all centers, and the 95% confidence interval (CI) for the odds ratio. To make the estimate of the odds ratio more interpretable, the interval estimate of the odds ratio per 6-month time period is presented, rather than the per day estimate. All statistical tests were two-sided.


    RESULTS
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
Patient Characteristics

Between July 1, 1997, and December 31, 2000, 3075 eligible patients with AJCC Stage Group I and II (0–5 cm) breast cancer entered onto the NCCN Breast Cancer Outcomes Project at five participating comprehensive cancer centers. Of these patients, 3003 (98%) had their definitive surgery before December 31, 2000, and thus were considered evaluable for analysis. As shown in Table 1Go, 74% of tumors were 2 cm or less in size and 65% of tumors were lymph node–negative. Type of definitive surgery was breast-conserving surgery in 59% of patients and mastectomy in 41% of patients. Types of axillary surgery were SNB alone in 13%, SNB + AND in 22%, AND alone in 59%, and no axillary surgery in 6% of patients.


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Table 1. Patient characteristics for 3003 patients with stage I and II breast cancer (tumor size <=5.0 cm) in the National Comprehensive Cancer Network Breast Outcomes Project
 
Patterns of Axillary Surgery According to Definitive Surgery Type

Patterns of axillary surgery varied substantially by definitive surgery type (Table 2Go). Among patients treated with mastectomy, SNB alone was performed in only 3% of patients and SNB + AND was performed in 15% of patients. In contrast, among patients treated by breast-conserving surgery, SNB alone was performed in 20% of patients and SNB + AND was performed in 28% of patients. The use of SNB alone was statistically significantly associated with breast-conserving surgery (in logistic regression), when controlling for stage and center (P<.001). Because use of SNB alone was statistically significantly associated with breast-conserving surgery and infrequently performed with mastectomy, and because the presence of additional lymph nodes in a mastectomy could confound classification of axillary surgery with mastectomy, further examination of the trends in use of SNB over the 3.5-year analysis period was limited to the 1763 patients treated with breast-conserving surgery.


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Table 2. Type of axillary surgery stratified by definitive surgery for patients with stage I and II breast cancer (tumor size <=5.0 cm) in the National Comprehensive Cancer Network Breast Outcomes Project*
 
Patterns of Axillary Surgery Among Patients Who Received Breast-Conserving Surgery

Among women who received breast-conserving surgery, there was a statistically significant association between type of axillary surgery and tumor size, stage, and age, controlling for center (Table 3Go; P<.001 for all three associations). SNB alone was more commonly used for women with small tumors (<=2 cm) than for women with large tumors (2–5 cm) (22% versus 14%, respectively), whereas AND alone was less commonly used for women with small tumors than for those with large tumors (39% versus 59%, respectively). SNB alone was also more commonly used for women with stage I than stage IIA or IIB tumors (26% for stage I versus 13% for stage IIA and 3% for stage IIB), whereas AND alone was used more frequently for women with stage IIB than stage I or stage IIA tumors (36% for stage I, 48% for stage IIA, and 67% for stage IIB). SNB alone was used in only 3% of patients with positive lymph nodes (i.e., histologically positive sentinel nodes [data not shown]), probably because these patients declined AND. The type of axillary surgery also varied by patient age, with patients older than 70 years more likely to have no axillary surgery (None) than patients in the other three age groups (34% versus 3%, 3%, and 9% in the <50, 50–59, and 60–69 year age groups, respectively; Table 3Go).


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Table 3. Type of axillary surgery by tumor size, tumor stage, and age group for patients with stage I and II breast cancer (tumor size <=5.0 cm) who received breast-conserving surgery (N = 1763)*
 
Time Trends of SNB Use Among Patients Who Received Breast-Conserving Surgery

Temporal trends in the use of SNB among patients undergoing breast-conserving surgery are shown in Fig. 1Go. The percentages represent the unweighted averages of the proportion of axillary surgery types across the five participating cancer centers. Among patients with smaller tumors (<=2 cm), the use of SNB alone rose steadily throughout the study period, with a concomitant decline in the use of AND and no axillary surgery (Fig. 1, AGo; odds ratio for the use of SNB alone per 6-month time period = 2.27, 95% CI = 1.90 to 2.70; Ptrend<.001). Use of SNB + AND rose in the early years between 1997 and 1999 and subsequently declined by the end of 2000. By the last 6 months of the study period, the average percentage of patients receiving SNB alone across the five centers was 50% (range = 27%–66%), whereas the average percentage of patients receiving SNB + AND was 32% (range = 9%–73%). As shown Fig. 1, BGo, although SNB alone seemed to be adopted more slowly among patients with larger tumors (>2.0–5.0 cm) than it was among patients with smaller tumors (<=2.0 cm), the time trend for adoption of SNB alone remained statistically significant in this group (odds ratio for the use of SNB alone per 6-month time period = 2.05, 95% CI = 1.39 to 3.02; Ptrend<.001).



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Fig. 1. Time trends for the use of axillary surgery (aggregated into 6-month intervals) for the five comprehensive cancer centers from July 1997 through December 2000. A) Average proportion of patients with stage I and II breast cancer who received breast-conserving surgery for invasive breast tumors that were 0–2.0 cm. B) Average proportion of patients with stage I and II breast cancer who received breast-conserving surgery for invasive breast tumors that were >2.0–5.0 cm. Axillary surgery was categorized as sentinel node biopsy (SNB) alone (solid diamonds), SNB plus axillary node dissection (AND) (solid circles), AND alone (solid squares), or no axillary surgery (None) (open circles).

 
The best indicator of the use of SNB as routine care is its use without AND for stage I cancer patients. AND is combined with SNB in this group of patients only for surgeon training, technique validation, or when dictated by an investigational protocol. In 1997, the five comprehensive cancer centers used SNB alone in 8% of patients on average, whereas SNB + AND was used in 23% of patients on average (Table 4Go). By the second half of 2000, the average use of SNB alone had risen to 58%. There was an initial increase in the use of SNB + AND until the last half of 1999 (37%); however, use of SNB + AND then decreased as the use of SNB alone increased. There was a statistically significant association (modeled by logistic regression) between SNB alone and the date of surgery, controlling for center, age, and comorbidity (odds ratio for use of SNB alone per 6-month time period = 2.30, 95% CI = 1.88 to 2.82; Ptrend<.001).


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Table 4. Type of axillary surgery for patients with stage I breast cancer who received breast-conserving surgery between July 1997 and December 2000*
 
Center-Specific Patterns in Types of Axillary Surgery

Although there were steady increases in the percentage of patients treated with SNB over the study period, there was wide variation among centers with respect to the use of SNB for stage I cancer patients who received breast-conserving surgery (Table 4Go). For example, in late 2000, 58% of patients with stage I cancer were treated with SNB alone. However, for individual centers, the percentage of patients treated with SNB alone ranged from 30% to 82% in this time period. The association of definitive surgery timing and SNB alone versus other types of axillary surgery was statistically significant in logistic regression analysis, controlling for center, age, and comorbidity (Ptrend<.001).

The percentage of patients with stage I breast cancers treated with SNB alone and with SNB + AND at each center are shown Fig. 2, A–EGo. Center 1 had a higher rate of SNB alone than of SNB + AND from the start of the study period. Centers 2–4 demonstrated a similar pattern for the use of SNB, with an initially greater use of SNB + AND, subsequently replaced by greater use of SNB alone. For Center 5, SNB + AND was used throughout the study period. Although use of SNB alone was on the rise by the end of the study period, it never exceeded use of SNB + AND at Center 5. The time point for the introduction of SNB + AND and SNB alone varied among centers. The five centers are displayed in order according to when the percentage of patients treated with SNB alone first exceeded the percentage of patients treated with SNB + AND. For Center 1 (Fig. 2, AGo), this crossover point presumably occurred before the observation period. For Centers 2 and 3 (Fig. 2, B and CGo), this crossover point occurred during 1999. In contrast, for Center 4 (Fig. 2, DGo), this crossover point occurred in early 2000 (i.e., January–June), whereas for Center 5 (Fig. 1, EGo), this crossover point had not occurred by the end of the study period (i.e., July–December 2000).



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Fig. 2. A–E) Center-specific time trend for the percentage of patients with stage I breast cancer receiving breast-conserving surgery for all five comprehensive cancer centers. Axillary surgery was categorized as sentinel node biopsy (SNB) alone (solid circles) and SNB plus axillary node dissection (AND) (open squares).

 

    DISCUSSION
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
This study examined patterns of axillary surgery use for stage I and II breast cancer patients at the five comprehensive cancer centers that established the NCCN Breast Cancer Outcomes Project in the time frame coincident with the introduction of SNB. In 1997, most patients at these cancer centers received standard AND. Over the ensuing 3 years, every center introduced SNB and omitted AND for at least some patients with negative lymph nodes. SNB was most commonly used in patients who received breast-conserving surgery, and its use was statistically significantly associated with smaller cancer size (i.e., 0–2 cm) and histologically negative lymph nodes.

In examining time trends for the use of SNB, we chose to focus particularly on patients with small tumors and negative axillary lymph nodes treated with breast-conserving surgery because the nature of the primary or axillary surgery performed in such patients is unlikely to influence the stage grouping; thus, comparison of patterns-of-care across centers is not confounded by clinical characteristics. In addition, AND is performed with SNB in these patients only for surgeon training, technique validation, or when dictated by an investigational protocol. Among such patients, we found that SNB was first used at each NCCN center in conjunction with AND. After a variable period of time, the frequency of the SNB + AND procedure in patients with negative lymph nodes decreased and the use SNB alone increased. This pattern may reflect an early "learning phase" during which the results of the SNB procedure were confirmed by AND in all patients, followed by a shift toward a "mature phase" in which AND was performed only if the sentinel lymph node was found to be positive. The center-specific time trends showed evidence of earlier versus comparatively later adoption of SNB alone, even among this small select group of similar comprehensive cancer centers. The time point at which SNB alone entered into routine clinical practice varied among the centers, possibly because of the beliefs and preferences of individual physicians at those centers. However, at a time when the NCI deemed SNB to be investigational and initiated clinical trials of the accuracy and efficacy of SNB, physicians at each of these NCI-designated comprehensive cancer centers were using SNB alone as routine treatment of breast cancer outside research protocols for some women.

The NCCN Breast Cancer Outcomes Project provides unique insights into the introduction of SNB. To our knowledge, there are no other comparable published reports on the extent of use of SNB in the United States. The only related data are the results from surveys of surgical practices of 410 respondents to a survey sent to 1000 randomly selected fellows of the American College of Surgeons; 77% (316/410) performed SNB for the treatment of breast cancer (36). In addition, a telephone survey of surgeons in U.S. Department of Defense hospitals in 2000 showed that 35% (23/66) of the Department of Defense hospitals performed SNB, of which 17 were still in the learning phase where the results of SNB were confirmed by AND (37). The time period we studied coincides with the publication of a large body of literature supporting the use of SNB and the incorporation of SNB into published practice guidelines (14,23,3842). Moreover, the NCCN breast cancer practice guidelines added the option of SNB as an alternative to AND in 1998 (24). Other research groups have also published similar breast cancer practice guidelines (25,26).

Widespread use of SNB in the routine care setting could affect accrual to and the generalizability of the results of ongoing clinical trials. The two ongoing NCI-sponsored trials are designed to determine the rate of false-negative sentinel lymph nodes, the hazard of regional failure after SNB, the impact of SNB on the choice of systemic therapy, and the effect of AND and SNB on survival (19,20). In the NSABP B-32 trial, SNB is performed on patients with clinically negative nodes. Patients in whom the sentinel lymph node is negative are randomly assigned to either SNB alone or SNB + AND. This trial will define the false-negative rate of SNB and the impact of AND on survival. In the ACOSOG Z0010 trial, patients in whom the sentinel lymph node is negative are followed without any randomization to a treatment group. The objectives of that study are to evaluate the prognostic significance of lymph node and bone marrow micrometastases and the rate of axillary failure with a negative SNB. Accrual to both trials began in 1999 and is still ongoing; data from these trials will not be available for many years.

Even if the accrual goals of these trials are met, the widespread use of SNB outside the clinical trials setting may bias the population of patients and surgeons participating in the trials and may affect the generalizability of the studies’ ultimate conclusions. Proficiency in the SNB technique requires substantial experience. Surgeons need to perform 20–30 SNB procedures combined with AND before they can achieve a high rate of accuracy (25,26,32,4345). With less experience, the collective rate of false-negative SNBs and failure to identify the sentinel lymph node are higher (4648). The NSABP B-32 trial requires surgeons to complete only five SNB training procedures before entering patients onto the trial. If the most experienced surgeons choose to use SNB as routine care, the surgeons who do participate in the NSABP B-32 trial may represent a less experienced and less proficient group. Hence, the NSABP B-32 trial could overestimate the rates of false-negative SNBs or axillary recurrence associated with the procedure compared with the rates that would have occurred had the most experienced surgeons participated in the trial. Although the ACOSOG trial requires surgeons to have performed 30 SNB procedures before study participation, this trial will report only on subsequent regional recurrence, not on the rate of false-negative SNBs or the impact of axillary surgery on survival.

Limitations of our study include the fact that we identify only the center within the NCCN Breast Cancer Outcomes Project database and not the individual surgeon; therefore, we cannot comment on surgeon-specific learning curves. In addition, our study provides information on the use of SNB in only five comprehensive cancer centers. Patterns of care among patients treated at other comprehensive cancer centers and in community practice may differ from those we observed. It is also possible that patients interested in the option of SNB preferentially chose to come to these centers for their surgery. However, no matter what the patient preferences were, physicians in these centers willingly provided SNB as routine care for the treatment of these patients.

In conclusion, physicians introducing new technologies into clinical practice must carefully weigh the potential advantages and risks of that technology. Although randomized clinical trials remain the standard to prove safety and efficacy, other paradigms for evaluating and accepting new technologies may be needed. More than a million patients in the United States alone will develop invasive breast cancer before clinical trial data on SNB are available. Delaying use of SNB pending trial results may lead to substantial morbidity including permanent lymphedema in a substantial proportion of invasive breast cancer patients. Our data suggest that the breast cancer teams at some NCI-designated comprehensive cancer centers have weighed the currently available evidence and have accepted SNB as standard care for the treatment of breast cancer. Whether widespread use of SNB represents good clinical judgment or an example of premature adoption of an inadequately tested new technology is a question that may only be resolved many years from now when, and if, the ongoing clinical trials of SNB provide definitive data on the outcomes of this technique.


    NOTES
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 
Supported in part by Public Health Service grant P50CA89393 to the Dana-Farber Cancer Institute from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services.

The NCCN Breast Cancer Outcomes Project acknowledges the efforts of clinical research associates at each participating center who collected and entered the data for this study.

1 Editor’s note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research. Back


    REFERENCES
 Top
 Notes
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 

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Manuscript received January 15, 2003; revised August 6, 2003; accepted August 15, 2003.


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