1 Breakthrough Breast Cancer Research Centre, London; 2 Mount Vernon Hospital, Northwood, Middlesex; 3 Royal Marsden Hospital, Sutton, Surrey; 4 Lincolns Inn Fields Laboratories, London; 5 Parkside Hospital, London, UK
* Correspondence to: Dr S. Cleator, The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, Fulham Road, London SW3 6JB, UK. Tel: +44-20-7970-6058; Fax: +44-20-7878-3858; Email: scleator{at}icr.ac.uk
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Abstract |
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Patients and methods: 309 women were randomised to primary surgery followed by eight cycles of adjuvant mitoxantrone, methotrexate with tamoxifen (2MT) or 2MT with mitomycin-C (3MT) versus the same regimen for four cycles before followed by four cycles after surgery. For this analysis the median follow-up of patients was 112 months.
Results: After 10 years follow-up there is still no statistically significant difference in disease-free survival (DFS) (71% versus 71%) or overall survival (OS) (63% versus 70%) when comparing adjuvant versus neoadjuvant treatment, respectively. Of 144 evaluable patients in the neoadjuvant arm, 74 achieved a good clinical response and 70 patients achieved a poor clinical response. Good responders had a superior DFS (80% versus 64%, P=0.01) and OS (77% versus 63%, P=0.03) compared to poor responders.
Conclusions: At 10 years, neoadjuvant and adjuvant treatment continue to have equivalent OS and DFS. Good clinical response to neoadjuvant chemotherapy is associated with superior DFS and OS. This supports the use of clinical response of primary breast cancer to neoadjuvant therapy as a surrogate marker of survival benefit.
Key words: breast cancer, chemotherapy, neoadjuvant, response, survival
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Introduction |
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The results of several randomised trials comparing adjuvant versus neoadjuvant chemotherapy/chemoendocrine therapy for operable breast cancer have now been published [611
]. None of the published trials show any difference in overall survival between the adjuvant and neoadjuvant arms. However, we have previously reported a relative reduction by neoadjuvant chemotherapy in requirement for mastectomy of
50% (28% to 13%) [12
]. Therefore neoadjuvant chemotherapy appears a safe approach which results in avoidance of otherwise unavoidable mastectomy in a significant proportion of women.
Neoadjuvant chemotherapy has proved a valuable research tool, providing the opportunity to observe the effects of cytotoxic drugs in vivo. There is a wealth of literature correlating clinical response with changes in measures of proliferation and apoptosis in breast cancers during treatment and with various pretreatment phenotypic features [13]. Underpinning these studies is the concept that biological markers, which are predictors for good response to neoadjuvant therapy may be surrogates of survival benefit from a given treatment. However, there is inconsistency in the literature with respect to the reported relationship between clinical response and overall survival, both in prospective randomised trials and retrospective series.
Between 1990 and 1995 a prospective randomised trial to evaluate the role of neoadjuvant chemotherapy was conducted at the Royal Marsden Hospital. Findings with respect to response rate, mastectomy requirement and 5-year outcome have been reported previously [8, 12
]. In this report we present an update of previously published data.
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Patients and methods |
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Patients were randomised to receive either appropriate primary surgery followed within 36 weeks by adjuvant chemoendocrine therapy plus radiotherapy if required (adjuvant arm), or primary chemoendocrine therapy for 3 months before and 3 months after appropriate surgery plus radiotherapy if required (neoadjuvant arm).
Clinical stage, size and position of primary tumour and appropriate primary surgical requirements were recorded at randomisation in all patients. Clinical size was measured as the product of the largest diameter and its perpendicular diameter. For patients in the neoadjuvant arm, clinical size of the tumour was recorded at 3-week intervals until the presurgical assessment at 3 months. These patients then had a repeat clinical assessment, mammography, breast ultrasound, and a clinical decision made on their surgical requirements.
Patients randomised to adjuvant therapy had appropriate surgery and radiotherapy according to the size and position of the primary tumour, followed by eight courses of chemotherapy with 3M (mitomycin C, 7 mg/m2 every 6 weeks, mitoxantrone 7 mg/m2 every 3 weeks and methotrexate 35 mg/m2 every 3 weeks, with dose modification according to blood count and symptomatic toxicity) or 2M (same as 3M, with the exclusion of mitomycin C and an increased dose of mitoxantrone to 11 mg/m2) and tamoxifen 20 mg per day for 5 years. Patients randomised to neoadjuvant therapy had four courses of 3M (or 2M) and tamoxifen, followed by four further courses of chemotherapy and tamoxifen for 5 years.
Mastectomy (usually with immediate reconstruction) was considered necessary if the tumour was located within 2 cm of the nipple or was large in comparison to breast size. Otherwise the tumour was excised sufficiently to achieve a high probability of complete surgical excision. Palpable axillary lymph nodes were removed by lower axillary sampling. No axillary procedure was performed for patients with clinically negative lymph nodes. The influence of combined chemoendocrine therapy on clinically undetectable axillary disease is unknown. Axillary node biopsy was not required as a prognostic indicator for systemic therapy. In patients who achieved a clinical complete response (CR), the location of surgical excision was determined by mammographic or ultrasound identification of residual scarring or as located before treatment.
All patients who did not require a mastectomy were given local postoperative radiotherapy to the breast with a dose of 54 Gy in 27 fractions over 5.5 weeks using two tangential fields, followed by a boost of 10 Gy to the tumour bed. Radiotherapy to the axilla and supraclavicular fossa was given for cases with histological evidence of axillary involvement on axillary sampling. Radiotherapy commenced 46 weeks after surgery and was given concurrently with chemotherapy.
The clinical measurement of the response to neoadjuvant therapy was undertaken by two independent observers and defined according to the International Union Against Cancer (UICC) criteria [14]. No palpable abnormality at this site indicated a CR, and >50% reduction in bidimensional measurements indicated a partial response (PR). A reduction of <50% in bidimensional measurements was recorded as no change (NC), while an increase in measurements of >25% represented progressive disease (PD). Patients with PD received early surgery with completion of the chemoendocrine therapy after surgery. A residual nodularity after a good response which was insufficient to be measured was classified as minimal residual disease (MRD). In this paper MRD and CR have been collectively referred to as good clinical response and PR, NC and PD as poor clinical response. Surgical specimens from patients who had received neoadjuvant therapy which no longer contained malignant cells (primary and lymph nodes) were defined as displaying a complete pathological response (pCR), in contrast to those found to contain residual invasive malignancy (pINV).
Survival was measured from primary diagnosis until death due to any cause. Disease-free survival was measured from primary diagnosis until first local or distant recurrence and was censored at death without a recurrence. Locoregional control was measured from diagnosis until first locoregional recurrence and was censored at metastatic relapse or death.
Statistical analysis
Treatment and response groups were compared for baseline demographics and treatment details by means of the chi-squared test or Fisher's exact test and the MannWhitney non-parametric test (age). Actuarial survival curves were calculated by the KaplanMeier method [15] and comparisons were made by means of the log rank test.
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Results |
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Table 1 shows patient (age, menopausal status and treatment received) and tumour characteristics (tumour and nodal stage) for patients in the adjuvant and neoadjuvant arms of the study. No statistically significant differences were noted between the two arms in terms of these characteristics. In our previous paper [8], outcome data to a median follow-up of 48 months showed no statistically significant difference between the two arms of the trial in terms of DFS, metastatic relapse (MFS) and OS. We now update this outcome analysis with a median follow-up of 112 months (range 12145 months) (Table 3). After this longer follow-up, DFS for adjuvant and neoadjuvant therapy was 71% and 71%. Corresponding figures for OS were 63% and 70% (P=0.6). Locoregional control (RLC) for adjuvant and neoadjuvant therapy was 94% and 91%, respectively (P=0.7). Metastatic control was 72% in patients receiving adjuvant and 76% in patients receiving neoadjuvant therapy (P=0.6).
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Discussion |
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There is considerable interest in the use of response to neoadjuvant chemotherapy as an early surrogate of long-term outcome. Previous studies have consistently shown that patients who achieve pCR have improved overall survival [10, 11
, 18
]. In this study we observed a superior overall and metastasis-free survival associated with a lack of residual invasive disease, but only the latter reached statistical significance, probably due to the small number of patients in this group. Thirteen percent (19/142) of patients in this study achieved a pCR, and none relapsed systemically. An update of the NSABP B-18 study at 10 years [10
] did not include figures for MFS and the definition of pCR related to the breast pathology alone (axillary node status not included), so it is difficult to compare the two sets of data. However, in most trials with anthracycline-based chemotherapy only 5%10% of patients achieve this end point [8
, 10
, 11
, 18
], thereby reducing its clinical usefulness as a surrogate of treatment benefit. Furthermore, pCR can only be determined after surgery and cannot be used to tailor treatment on an individual patient basis. In this study we compared the outcome in good clinical responders with poor responders. Good clinical responders, defined as those with either CR or MRD, accounted for
50% of the patients overall. This dichotomy makes this a more useful end point for trials where neoadjuvant chemotherapy is used as an in vivo model to define biological markers of response.
With long follow-up, our results show that good responders have superior outcome both in terms of DFS and OS. The improved outcome appears to be due largely to a difference in metastasis-free survival rather than a difference in locoregional control and hence to a difference in the extent of eradication of micrometastatic disease. This implies that micrometastases have the same chemosensitivity as their corresponding primary tumour. This is in line with studies that demonstrate a similar microarray expression profile to metastases and matched primaries [19].
The association of good outcome with good clinical response to neoadjuvant chemotherapy has been documented in previous studies by Bonnadonna and Valagussa [20] (improved DFS), Pierga et al. [21
] (improved OS) and Hortobagyi et al. [22
] (improved DFS). Improved outcome was also seen in the largest neoadjuvant trial (NSABP-B18) at 9 years of follow-up for both DFS and OS [10
]. However, several other neoadjuvant studies have failed to show an association [7
, 9
, 11
, 23
]. It is noted that the categorisation of responders and non-responders has not been consistent in these studies.
Tumour regression after neoadjuvant therapy can be assessed clinically, radiologically or pathologically. Clinical measurement has been criticised as being subject to inter-observer variation, and this may account for why some studies have failed to demonstrate improved outcomes in good responders. Single institution studies, such as ours, while limited in terms of patient numbers, have the advantage that they rely on a small number of clinicians performing such measurements and thereby achieve greater consistency. Radiological evaluation of response, either by ultrasound or mammography, has been used for this purpose. However, radiological response is also subject to inter-observer variation and the correlation with histology has not been consistently shown to be superior to that of clinical evaluation [24]. Furthermore, there are no studies with long-term follow-up showing improved outcome in patients achieving good radiological response.
There is currently considerable interest in the use of microarray profiling to predict response to neoadjuvant chemotherapy, although currently the associated error rate overall for prediction of pCR [25] or clinical response [26
] is high. This study demonstrates that poor response to chemotherapy is associated with poor outcome, and probably a lack of benefit from chemotherapy. It is probably most useful to develop the capacity to predict accurately, (of all subclasses of response), those patients who are poor clinical responders so that they may avoid non-beneficial chemotherapy. Indeed this is probably a more useful surrogate of outcome than pCR in terms of assigning adjuvant chemotherapy treatment, even though this study confirms that pCR defines a distinct group with extremely good outcome.
In summary, we have demonstrated that with long follow-up, equal survival is achieved from neoadjuvant and adjuvant chemoendocrine therapy. Local control remains high in both groups and is not significantly different between the two arms. None of the patients who achieved a pCR relapsed systemically. Patients who achieved good clinical response had an improved DFS and OS at 10 years compared with poor responders, indicating that clinical response can be used as an early surrogate of outcome.
Received for publication June 30, 2004. Revision received September 16, 2004. Accepted for publication September 17, 2004.
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