Purpose: This analysis was performed to clarify the relationship between the surgery-radiotherapy interval and the risk of recurrence in patients treated with breast-conserving therapy for early stage invasive cancers.
Methods and materials: We retrospectively analyzed data from 653 patients with American Joint Commission on Cancer Stage I or II, pathologically node-negative breast cancer treated by breast-conserving therapy without adjuvant systemic therapy between 1968 and 1985. All patients received a dose of at least 60 Gy to the tumor bed. Two hundred and eighty-three patients started radiotherapy within 4 weeks of surgery, 308 started 5-8 weeks after surgery, and 54 started 9-12 weeks after surgery. Median follow-up in the 531 survivors was 100 months.
Results: Pathologic features and treatment characteristics were well balanced between the groups with surgery-radiotherapy intervals of 0-4 weeks and 5-8 weeks. There was no statistically difference in the risk of overall recurrence among patients starting radiotherapy 5-8 weeks after surgery compared with those treated within 4 weeks. Analysis of the 5-year crude rates of failure further demonstrated no difference in the distribution of sites of failure in the 5-8 week group compared with the 0-4 week group. A multivariate model controlling for known risk factors, as well as potential treatment-related confounders, also failed to demonstrate an increased risk of recurrence with the longer surgery-radiotherapy interval (risk ratio = 0.89, p = 0.44).
Conclusion: This retrospective analysis suggests that a delay of up to 8 weeks in the interval between the last breast surgery and the start of radiotherapy is not associated with an increased risk of recurrence in patients with early stage breast cancer treated with breast irradiation to at least 60 Gy without systemic therapy.