Long-term outcome after postmastectomy radiation therapy for breast cancer patients at high risk for local-regional recurrence.

Purpose: Postmastectomy radiation therapy is often recommended for patients at high risk for local-regional recurrence after mastectomy. However, long-term outcomes after radiation therapy are not well described.

Patients and methods: Between 1977 and 1992, 221 patients at high risk for local-regional recurrence of breast cancer after mastectomy were treated with radiation therapy, with or without adjuvant systemic therapy. Patients were classified as high risk because of T3 or T4 tumors (14%), positive lymph nodes (29%), close or positive margins of resection (15%), or multiple risk factors (39%); 4% did not meet current criteria for radiation therapy. The median age of patients was 51 years. Radiation therapy consisted of 45 to 50.4 Gy to the chest wall in 1.8 to 2.0 Gy fractions. The regional lymph nodes were treated in 187 patients (85%). There were 151 patients (68%) who received adjuvant chemotherapy. Patients who received chemotherapy were younger (median age, 48 years vs 64 years) and had more positive lymph nodes (median, 5 vs 1) than patients not receiving chemotherapy. Adjuvant hormonal therapy was utilized in 116 patients (53%). The median follow-up was 4.3 years.

Results: The actuarial 10-year local-regional failure rate was 11% (95% CI: 6.5% to 16.7%). The site of first failure was distant metastases in 75 patients (34%), local-regional recurrence in 11 patients (5%), and both sites in three patients (1%); 60% had no evidence of disease at last follow-up. Of the patients who presented with local-regional recurrence as first failure, nine patients (82%) subsequently developed metastatic disease. The median time to local-regional first failure was 1.3 years. The median time to distant metastases after local-regional first failure was 0.3 years.

Discussion: Postmastectomy radiation therapy is associated with an 89% rate of local-regional control in this high-risk population. Patients who experience a local-regional recurrence after radiation therapy are at a very high risk for metastatic disease. Radiation therapy after mastectomy is recommended to optimize local-regional control for high-risk breast cancer patients.