Purpose: To study how the timing of radiation influences local control, overall survival, and disease-free survival in patients being treated with chemotherapy and radiation for a local-regional carcinoma of the breast.
Methods and materials: Over a ten year period, 105 patients received chemotherapy and radiation treatments for a local-regional breast cancer. The population was divided into two groups based on the timing of their radiation treatments. Forty-eight patients began their radiation within 6 months of their diagnosis (early radiation group). Fifty-seven patients had a delay in their radiation for 6 or greater months in order to first maximize chemotherapy treatments (delayed radiation group). There were no significant differences between the two groups with respect to nodal status, stage of the primary, estrogen receptor status, patient age, or type of surgery performed. The only prognostic parameter that was imbalanced was that of a greater percentage of patients with close or positive margins in the early radiation group compared to the delayed radiation group (69% versus 38%, p < 0.02).
Results: Comparisons of local control, overall survival, and disease-free survival between the early radiation patients and delayed radiation patients all favored the early radiation group. Respective 8-year actuarial rates were: local control--98% vs. 76%, p = 0.004; overall survival--80% vs. 52%, p = 0.016; disease-free survival--71% vs. 48%, p = 0.008. The differences continued to be significant in a multivariate Cox regression model comparison: p = 0.011, p = 0.050, p = 0.009. There was only one death from intercurrent disease, so that overall survival approximated cause-specific survival to an accurate degree.
Conclusions: In patients requiring chemotherapy and radiation treatments for a local-regional breast cancer, a delay in the initiation of radiation for a period of 6 months or greater from diagnosis resulted in a higher local failure rate. Furthermore, this higher local failure rate was associated with an increased rate of distant metastases and a decreased overall survival rate.