Screening mammography use and chemotherapy among female stage II colon cancer patients: a retrospective cohort study

BACKGROUND: Although chemotherapy is not a routine recommendation for stage II colon cancer by the U.S. national guidelines, 20-30% of patients have received chemotherapy. This study investigated whether screening mammography use before the cancer diagnosis was associated with chemotherapy use among female elderly patients with stage II colon cancer. METHODS: Retrospective cohort study on 2910 female stage II colon cancer patients aged 67-79 using the Surveillance, Epidemiology and End Results (SEER)-Medicare data (1996-2002). Screening mammography use and chemotherapy use were identified using Medicare claims data. Multivariate logistic regression and Kaplan-Meier curves were used. RESULTS: About 25% of female elderly patients received chemotherapy. The chemotherapy rates increased from 22% in 1996-1998 to 26% in 2001-2002. After adjusting for socio-demographic variables, tumor characteristics and Charlson index for comorbidities, the odds of receiving chemotherapy were 28% higher among those who had a screening mammogram before the cancer diagnosis than those who did not (OR: 1.28, 95% CI: 1.07-1.54). Those with a prior mammogram also received chemotherapy earlier than those without. In addition, patients with unfavorable tumor characteristics were more likely to receive chemotherapy. Mammography use before the cancer diagnosis was associated with favorable tumor characteristics. CONCLUSIONS: Despite the controversy about the chemotherapy use among stage II colon cancer, female elderly patients still received chemotherapy at a high rate. Our findings suggest that patient's health beliefs and health care seeking behavior, together with physician's recommendation, play important roles in the cancer treatment decision.