Abstract
PURPOSE: We evaluated the benefit of the current clinical practice of adjuvant chemotherapy for postmenopausal women with early-stage, estrogen- or progesterone-receptor-positive (er/pr+), one-to-three positive axillary lymph node (1-3 ln+), breast cancer (esbc). METHODS: Using the Manitoba Cancer Registry, we identified all postmenopausal women diagnosed with er/pr+ 1-3 ln+ esbc during the periods 1995-1997, 2000-2002, and 2003-2005 (n = 156, 161, and 171 respectively). Treatment data were obtained from the Manitoba Cancer Registry and by linkage with Manitoba administrative databases. Seven-year survival data were available for the 1995-1997 and 2000-2002 populations. Using Cox regression, we assessed the independent effect of the clinical practice of adjuvant chemotherapy on disease-free (dfs) and overall survival (os). RESULTS: Clinical breast cancer treatments did not differ significantly between the 2000-2002 and 2003-2005 populations. Adjuvant chemotherapy was administered in 103 patients in the 2000-2002 population (64%) and in 44 patients in the 1995-1997 population [28.2%; mean difference: 36%; 95% confidence interval (ci): 31% to 40%; p < 0.0001]. Compared with 1995-1997, 2000-2002 was not significantly associated with an incremental dfs benefit for patients over a period of 7 years (2000-2002 vs. 1995-1997; adjusted hazard ratio: 0.98; 95% ci: 0.64 to 1.4). CONCLUSIONS: The treatment standard of adjuvant chemotherapy in addition to endocrine therapy may not be effective for all women with er/pr+ 1-3 ln+ esbc. There could be a subgroup of those women who do not benefit from adjuvant chemotherapy as expected and who are therefore being overtreated. Further studies with a larger sample size are warranted to confirm our results.