A population-based study of the impact of delaying radiotherapy after conservative surgery for breast cancer.

BACKGROUND

Practice guidelines have set a maximum waiting time to radiation therapy for breast cancer. We evaluated if delaying radiotherapy resulted in worse outcomes in a large cohort of women with node-negative breast cancer.

METHODS

We selected a random sample of cases among women diagnosed with localized breast cancer in five regions of Québec, Canada, between 1988 and 1994. Only women with pathologically (n = 926) or clinically (n = 136) negative axillary nodes, and stage 1 or 2 disease treated with conservative surgery and radiotherapy were eligible. Information was obtained by chart review, queries to physicians and linkage with administrative databases. Outcomes were estimated by Kaplan-Meier method and Cox proportional hazards analysis. Median follow-up was 7.1 years (range: 0.9-11.8).

RESULTS

Median delay to radiotherapy was 12.4 weeks in those who received chemotherapy and 8.4 weeks in others. Overall survival at 7 years was 85.6%. Local relapse-free and distant disease-free survivals were 77.6 and 76.2%. There was no significant difference in survival according to delay to radiotherapy in crude or multivariate analysis adjusting for several prognostic factors, including systemic treatment. The risk of local failure conditional on survival in women who received radiotherapy more than 12 weeks after surgery was increased (hazard ratio: 1.75, 95% confidence interval: 1.00, 3.08, p-value = 0.052).

CONCLUSIONS

Although longer waiting time to radiotherapy may compromise local control, it does not influence survival at 7 years when other predictors of outcomes are taken into account. Well controlled studies are needed to confirm and better characterize this relationship.