Predictors of timing of adjuvant chemotherapy in older women with hormone receptor-negative, stages II-III breast cancer.

Adherence to consensus guidelines for cancer care may vary widely across health care settings and contribute to differences in cancer outcomes. For some women with breast cancer, omission of adjuvant chemotherapy or delays in its initiation may contribute to differences in cancer recurrence and mortality. We studied adjuvant chemotherapy use among women with stage II or stage III, hormone receptor-negative breast cancer to understand health system and socio-demographic correlates of underuse and delayed adjuvant chemotherapy. We used Surveillance Epidemiology and End Results (SEER)-Medicare linked data to examine the patterns of care for 6,678 women aged 65 and older diagnosed with stage II or stage III hormone receptor-negative breast cancer in 1994-2002, with claims data through 2007. Age-stratified logistic regression was employed to examine the potential role of socio-demographic and structural/organizational health services characteristics in explaining differences in adjuvant chemotherapy initiation. Overall utilization of guideline-recommended adjuvant chemotherapy peaked at 43% in this population. Increasing age, higher co-morbidity burden, and low-income status were associated with lower odds of chemotherapy initiation within 4 months, whereas having positive lymph nodes, more advanced disease, and being married were associated with higher odds (P < 0.05). Health system-related structural/organizational characteristics and race/ethnicity offered little explanatory insight. Timely initiation of guideline-recommended adjuvant chemotherapy was low, with significant variation by age, income, and co-morbidity status. Based on these findings, future studies should seek to explore the more nuanced reasons why older women do not receive chemotherapy and why delays in care occur.