1. ABSTRACT Purpose This retrospective review was conducted to determine if delay in the start of radiotherapy after conservative breast surgery had any detrimental effect on local recurrence in node-negative breast cancer patients. Method and Materials A total of 568 patients with T1-T2, N0 breast cancer were treated with breast-conserving surgery and breast irradiation, without adjuvant systemic therapy, between January 1, 1985 and December 31, 1992 at the London Regional Cancer Centre. Within this group, 63 patients (11.1%) had known positive or close resection margins ( 8-12 weeks (235 patients), > 12-16 weeks (91 patients) and > 16 weeks (41 patients). For the patients with positive or close resection margins, the time intervals used for analysis were 0-8 weeks (19 patients), > 8-12 weeks (29 patients) and > 12 weeks (15 patients). For patients age 8 weeks (25 patients). Kaplan-Meier estimates of time to local recurrence and disease-free survival rates were calculated. The association between surgery-radiotherapy interval and local recurrence and disease-free survival were investigated using Cox regression techniques. Results Median follow up was 11.2 years. Patients in the four time intervals were similar in terms of age and pathologic features. There was no statistically significant difference between the four groups in local recurrence or disease-free survival with surgery-radiotherapy interval (p=0.46 and p=0.18 respectively). The overall local recurrence rate at 5 and 10 years was 4.6% and 8.8% respectively. For patients age 8-12 weeks) 10.7% and 10.7% respectively and (> 12 weeks) 13.4% and 22.0% respectively. Conclusion This retrospective study suggests that delay in the start of breast irradiation beyond 12 and up to 16 weeks does not increase the risk of local recurrence in node-negative breast cancer patients. However, for patients with positive or close resection margins, this small patient population suggests that delay in breast irradiation beyond 12 weeks after definitive breast surgery may be associated with an increased risk of local recurrence. Also, young patients have an increased local recurrence rate and these recurrences occur early. The certainty of these results is limited by the retrospective nature of this analysis and the small number of patients in the subgroup analysis. Pattern Of Local Recurrence With Delay In Breast Irradiation In Patients With Positive Or Close Resection Margins And Young Age And Node Negative Disease Olga Vujovic, MD 1, Anil Cherian, MD 2, Edward Yu, MD 1, A.Rashid Dar, MD 1, Larry Stitt, MSc 3, Francisco Perera, MD 1 Departments of 1. Radiation Oncology, 2. Medical Oncology, 3. Biometry, London Regional Cancer Centre, London, Ontario, Canada Method A retrospective chart review was conducted of 568 patients with T 1 -T 2, N 0 breast cancer treated with breast-conserving surgery and breast irradiation, without adjuvant systemic therapy, between Jan 1/85 and Dec 31/92 at the London Regional Cancer Centre 63 patients (11.1%) had known positive or close resection margins (< 2 mm) 48 patients (8.4%) were age < 40 yrs at diagnosis Time intervals from definitive breast surgery to breast irradiation used for analysis were: 0-8 wks (201 pts), >8-12 wks (235 pts), >12-16 wks (11 pts) and >16 wks (41 pts) For pts with positive or close resection margins, the time intervals used for analysis were: 0-8 wks (19 pts), >8-12 wks (29 pts), and >12 wks (15 pts) For patients age 8 wks (25 pts) Results Median follow-up was 11.2 yrs Patients in the four time intervals were similar in terms of age and pathologic features There was no statistically significant difference between the four groups in local recurrence or disease-free survival with surgery - radiotherapy interval (p=0.46 and p=0.18 respectively) Overall local recurrence rate at 5 and 10 years was 4.6% and 8.8% respectively For patients age < 40, the local recurrence rate at 5 and 10 yrs was 17.2% and 19.8% respectively Also, there was no statistically significant difference between the two groups in local recurrence rate with surgery - radiotherapy interval (p=0.44) For patients age < 40 and with positive or close resection margins (8 pts) the local recurrence rate was 25.0% (2 failures) and these failures both occurred within 12 months (see Figure 1) Figure 1: Local Recurrence as a Function of Young Age and Margin Status Results for Positive or Close Resection Margins Overall 5 and 10 year local recurrence rate for pts with positive or close resection margins was 6.3% and 12.1% respectively The 5 and 10 year local recurrence rates for the 3 patient groups with positive or close resection margins were (See Figure 2): - 0-8 wks: 0% and 12.5% respectively - 8-12 wks: 10.7% and 10.7% respectively - 12 wks: 13.4% and 22.0% respectively Figure 2: Local Recurrence as a Function of Positive/Close Margins and Surgery- Radiotherapy Interval Conclusions 1. This retrospective study suggests that delay in the start of breast irradiation does not increase the risk of local recurrence in node-negative breast cancer patients, for a surgery-radiotherapy interval of up to 16 weeks. 2. However, for patients with positive or close resection margins, this small patient population suggests that delay in breast irradiation beyond 12 weeks after definitive surgery may be associated with an increased risk of local recurrence. 3. Young patients, age < 40 years have an increased local recurrence rate and these recurrences occur early, especially in those patients with positive or close resection margins.