Abstract P5-10-08: Evaluating the Efficacy of Current Clinical Practice of Adjuvant Chemotherapy in Post-Menopausal Women with One to Three Positive Auxiliary Nodes and Estrogen and/or Progesterone Positive Early Stage Breast Cancer
Authors: Hannouf MB , Brackstone M , Zaric G. 
Published: April 2011

Abstract
Background: Within the last decade, adjuvant chemotherapy has become the treatment standard for post-menopausal women with one to three positive auxiliary lymph nodes (LN+) and estrogen and/or progesterone positive (ER+/PR+) early stage breast cancer (ESBC). Recent data suggest that many of these women do not benefit from chemotherapy. We aimed to evaluate whether the current clinical practice of adjuvant chemotherapy in post-menopausal women with 1-3 LN+ and ER+/PR+ ESBC is associated with incremental survival benefit versus previous standard treatment of adjuvant hormone therapy alone for the majority of these women. Methods: We used the Manitoba Cancer Registry to identify all post-menopausal women diagnosed with LN+ and ER+/PR+ ESBC during the periods of January 1995 to December 1997, January 2000 to December 2002, and January 2003 to December 2005 (n= 156, 163 and 171, respectively). Treatment data including surgery and adjuvant therapy for all women were obtained from the Manitoba Cancer Registry and by linking with the Manitoba Administrative Databases. Five-year survival data were available for those who were diagnosed during the periods of 1995 to 1997 and 2000 to 2002 and were also obtained from the Manitoba Cancer Registry. Clinical practice of adjuvant chemotherapy was not found to differ during the time period of 2000 to 2005. Therefore, the earlier two cohorts diagnosed during the time period of 2000 to 2002 and 1995 to 1997 were only included in this analysis to reflect the current versus the previous clinical practice of adjuvant chemotherapy. In this retrospective analysis, we assessed the independent effect of the clinical practice of adjuvant chemotherapy on disease-free survival (DFS) and overall survival (OS) using Cox regression, adjusting for comorbid indices and receipt of radiotherapy.
Results: Age, clinical tumour size, tumour grade, and receipt of breast cancer surgery and endocrine therapy did not differ significantly between the two cohorts. There were 104 patients (64%) of those who were diagnosed later (2000-2002) versus 44 patients (28%) of those who were diagnosed earlier (1995-1997) who received chemotherapy (mean difference= 36%, 95% CI= 25% to 35%, p = 0.01). The 5-year Kaplan-Meier estimate of DFS of patients diagnosed later did not differ significantly than those diagnosed earlier (DFS= 78% versus 73%, respectively, log-rank test p =0.57). The multivariate Cox Regression analysis demonstrated that patients in the later versus the earlier cohort were not significantly associated with incremental DFS benefit over 5 years (2000-2002 vs. 1995-1997, hazard ratio: 1.04; p = 0.7). Similar results were seen for OS over 5 years (2000-2002 vs. 1995-1997, hazard ratio: 1.06; p = 0.65).
Conclusion: The treatment standard of adjuvant chemotherapy in addition to endocrine therapy for the majority of women with 1-3 LN+ and ER+/PR+ ESBC was not found to be associated with incremental survival benefit in comparison with previous standards. Our results suggest that a large number of patients with 1-3 LN+ and ER+/PR+ ESBC may not gain benefit from adding chemotherapy to endocrine therapy.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-10-08.