Background: Although the efficacy of adjuvant chemotherapy in prolonging survival for women with breast cancer has been well documented, limited population-based information is available on the actual use of chemotherapy.
Objective: To examine the relationship between age and chemotherapy use.
Design: Cohort study.
Setting: New Mexico.
Patients: 5101 women 20 years of age or older receiving a diagnosis of stage I, stage II, or stage IIIA breast cancer from 1991 through 1997.
Measurements: Pattern of chemotherapy use by age; logistic regression analysis to generate the odds and probabilities of receiving chemotherapy; and sensitivity analysis to estimate potential effects of unmeasured confounders.
Results: Overall, 29% of women received chemotherapy. The rate of chemotherapy use for women with stage I, stage II, or stage IIIA breast cancer was 11%, 47%, and 68%, respectively. Across all tumor stages, the use of chemotherapy decreased substantially with increasing age (P < 0.001). Overall, 66% of women younger than 45 years of age received chemotherapy compared with 44% of women between 50 and 54 years of age, 31% of women between 55 and 59 years of age, and 18% of women between 60 and 64 years of age. The decreasing pattern of chemotherapy use with age continued after adjustment for prognostic factors and was relatively insensitive to changes in unmeasured factors.
Conclusions: There is considerable discrepancy between the 1990 National Institutes of Health Consensus Conference recommendations for chemotherapy administration in women with breast cancer and the actual use of chemotherapy in the community. The decrease in use with age may relate to the decreasing efficacy of chemotherapy with age, as reported in clinical trials. Outcomes studies should address whether the recommendations are overly aggressive or whether practicing oncologists are too conservative in their use of chemotherapy.