CORRESPONDENCE

Re: Trends in Use of Adjuvant Multi-Agent Chemotherapy and Tamoxifen for Breast Cancer in the United States: 1975–1999

Xianglin L. Du

Correspondence to: Xianglin L. Du, M.D., Ph.D., Department of Internal Medicine, University of Texas Medical Branch, 3.134 Jennie Sealy Hospital, 301 University Blvd., Galveston, TX 77555–0460 (e-mail: xdu{at}utmb.edu).

Mariotto et al. (1) presented unique information on trends in use of adjuvant chemotherapy and tamoxifen for breast cancer in the United States from 1975 through 1999, using data from eight registries of the SEER1 program. In their study, information on adjuvant chemotherapy from the Patterns of Care studies was also used to correct the SEER bias due to underreporting (1). We used national population-based Medicare claims data from 1991 through 1996 to study temporal changes in adjuvant chemotherapy administration for breast cancer in women aged 65 years or older who were identified by the 11 SEER registries as having been diagnosed with stage I–IIIA breast cancer during this period (2). The internal validity of Medicare claims information on chemotherapy for breast cancer is good (2,3), and a recent external validation study comparing Medicare claims with medical chart and physician reviews showed a 98% agreement and a kappa of 0.82 (4). In our recent multivariable logistic regression re-analysis that was performed for 30 644 women with stage I–IIIA breast cancer from the 11 SEER registries and adjusted for age (65–69, 70–74, 75–79, or 80 or more years), ethnicity, marital status, cancer stage, tumor size, lymph node status, estrogen receptor status, comorbidity score, and SEER area, women diagnosed in 1996 were statistically significantly more likely to receive adjuvant chemotherapy than women diagnosed in 1991 (odds ratio = 1.28, 95% confidence interval = 1.09 to 1.51). Statistically significant interactions were observed among age, tumor stage, and year of diagnosis. After adjustment for the above variables, the increase in the likelihood of receiving adjuvant chemotherapy was statistically significant in all four age groups for women with stage II breast cancer, whereas for women with stage IIIA breast cancer, the increase was statistically significant only for women who were aged 65–69 or 70–74 years. Mariotto et al. (1) made a similar observation. However, in contrast to Mariotto et al., we found no statistically significant increase over time in use of adjuvant chemotherapy from 1991 to 1996 among older women with stage I breast cancer in any of the four age groups (2).

Age is a strong factor in determining adjuvant chemotherapy use for patients with breast cancer (13,5,6), even after controlling for comorbidity and patient and tumor characteristics (2,3). The influence of age was seen even in younger women 20–64 years of age with high-risk breast cancer (e.g., lymph node-positive tumors or lymph node-negative tumors larger than 1.0 cm that are hormone receptor-negative), for whom adjuvant chemotherapy is generally recommended (6). Although randomized trials have shown efficacy of adjuvant chemotherapy in women younger than 70 years, adjuvant chemotherapy has not been found to have an effect on recurrence and mortality in women aged 70 years or older (7).

Despite the lack of evidence about the benefit of adjuvant chemotherapy in women aged 70 years or older, both Mariotto et al. (1) and our group (2) have found an increase over time in use of chemotherapy in these women. One reason for this increase may be that the well-established benefit of adjuvant chemotherapy in women aged 69 years or younger with operable breast cancer may have influenced some oncologists to recommend chemotherapy in older women. Further studies will be needed to determine the benefits of adjuvant chemotherapy in women aged 70 years or older with operable breast cancer.

NOTES

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

1 Mariotto A, Feuer EJ, Harlan LC, Wun LM, Johnson KA, Abrams J. Trends in use of adjuvant multi-agent chemotherapy and tamoxifen for breast cancer in the United States: 1975–1999. J Natl Cancer Inst 2002;94:1626–34.[Abstract/Free Full Text]

2 Du XL, Goodwin JS. Increase of chemotherapy use in older women with breast carcinoma from 1991 to 1996. Cancer 2001;92:730–7.[CrossRef][Medline]

3 Du XL, Goodwin JS. Patterns of use of chemotherapy for breast cancer in older women: findings from Medicare claims data. J Clin Oncol 2001;19:1455–61.[Abstract/Free Full Text]

4 Warren JL, Harlan LC, Fahey A, Virnig BA, Freeman JL, Klabunde CN, et al. Utility of the SEER-Medicare data to identify chemotherapy use. Med Care 2002;40(8 Suppl): IV-55–61.

5 Harlan LC, Abrams J, Warren JL, Clegg L, Stevens J, Ballard-Barbash R. Adjuvant therapy for breast cancer: practice patterns of community physicians. J Clin Oncol 2002;20:1809–17.[Abstract/Free Full Text]

6 Du XL, Key CR, Osborne C, Mahnken JD, Goodwin JS. Discrepancy between consensus recommendations and actual community use of adjuvant chemotherapy in women with breast cancer. Ann Intern Med 2003;138:90–7.[Abstract/Free Full Text]

7 Polychemotherapy for early breast cancer: an overview of the randomised trials. Early Breast Cancer Trialists’ Collaborative Group. Lancet 1998;352:930–42.[CrossRef][Medline]



             
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