DOES DELAY IN BREAST IRRADIATION FOLLOWING CONSERVATIVE BREAST SURGERY IN NODE-NEGATIVE BREAST-CANCER PATIENTS HAVE AN IMPACT ON RISK OF RECURRENCE

Purpose: This retrospective review was conducted to determine if delay in the start of radiotherapy after definitive breast surgery had any detrimental effect on local recurrence or disease-free survival in nod e-negative breast cancer patients. Methods and Materials: A total of 5 68 patients with T1-T2, NO breast cancer were treated with breast-cons erving surgery and breast irradiation, without adjuvant systemic thera py between January 1, 1985 and December 31, 1992, at the London Region al Cancer Centre. Adjuvant breast irradiation consisted either of 50 G y in 25 fractions or 40 Gy in 15 or 16 fractions, followed by a boost of 10 Gy or 12.5 Gy to the lumpectomy site. The time intervals from de finitive breast surgery to breast irradiation used for analysis were 0 -8 weeks (201 patients), > 8-12 weeks (235 patients), > 12-16 weeks (9 1 patients), and > 16 weeks (41 patients). The time intervals of 0-12 weeks (436 patients) and > 12 weeks (132 patients) were also analyzed. Kaplan-Meier estimates of time to local recurrence and disease-free s urvival rates were calculated. The association between surgery-radioth erapy interval, age (less than or equal to 40, > 40 years), tumor size (less than or equal to 2, > 2cm), Scharf-Bloom-Richardson (SBR) grade , resection margins, lymphatic vessel invasion, extensive intraductal component, and local recurrence and disease-free survival were investi gated using Cox regression techniques. Results: Median follow-up was 6 3.5 months. Patients in all 4 time intervals were similar in terms of age and pathologic features. There was no statistically significant di fference between the 4 groups in local recurrence or disease-free surv ival with surgery-radiotherapy interval (p = 0.189 and p = 0.413, resp ectively). The 5-year freedom from local relapse was 95.4%. The crude local recurrence rate was 6.9% (7.8% for 436 patients treated within 1 2 weeks (median follow-up 67 months) and 3.8% for 132 patients treated > 12 weeks from surgery (median follow-up 52 months). In a stepwise m ultivariable Cox regression model for disease-free survival, allowing for entry of known risk factors, tumour size (p < 0.001), grade (p < 0 .001), and age (p = 0.048) entered the model, but the surgery-radiothe rapy interval did not enter the model. Conclusion: This retrospective study suggests that delay in start of breast irradiation beyond 12 and up to 16 weeks does not increase the risk of recurrence in node-negat ive breast cancer patients. The certainty of these results are limited by the retrospective nature of this analysis and the lack of informat ion concerning the late local failure rate. (C) 1998 Elsevier Science Inc.