Effectiveness of Adjuvant Chemotherapy for Node-Positive Operable Breast Cancer in Older Women

Background. Randomized clinical trials have shown the efficacy of adjuvant chemotherapy in treating node-positive operable breast cancer in women aged 69 years, but the benefit of chemotherapy in women aged 70 is questionable. This study was to examine if adjuvant chemotherapy is effective for these women with breast cancer. Methods.We studied a cohort of 5464 women diagnosed with node-positive operable breast cancer at age 65 in 1992 through 1996 with last follow-up of December 31, 1999 in five states and six metropolitan areas. Hazard ratio (HR) for all-cause mortality was used for survival analysis with adjustment for patient and tumor characteristics; propensity analysis was used to control for observed factors; and sensitivity analysis was used to estimate potential effects of unmea-sured confounders. Results. After adjusting for propensity to receive chemotherapy, the chemotherapy-treated and untreated groups were not statistically significantly different for covariates except for age and hormone receptor status. Mortality was significantly reduced in women aged 65–69 who received adjuvant chemotherapy compared to those who did not, after adjusting for patient and tumor characteristics (HR 0.70, 95 % confidence interval [CI], 0.57–0.88) or after adjusting for propensity scores (HR 0.76, 95 % CI, 0.62–0.94). HR did not significantly differ between the treated and untreated women aged 70 (HR 0.96, 95 % CI 0.83–1.09, and HR 0.99, 95 % CI, 0.87–1.14). These results were relatively insensitive to changes in unmeasured confounders