Microscopic residual disease is a risk factor in the primary treatment of breast cancer

Objectives: In the primary treatment of breast cancer, postoperative radiotherapy is performed in high-risk patients after mastectomy and in patients who received breast conserving surgery. In a retrospective analysis, our mono-institutional results of postoperative irradiation have been evaluated. Patients and Methods: Between 1992 and 1996, 500 patients have been irradiated after surgery for primary breast cancer. Of these, 489 patients had no initial metastases. 89 patients with loco-regional disease had a mastectomy, 400 patients were irradiated after breast conserving surgery. Radiotherapy at the chest wall was performed with 50 Gy and 2 Gy fractions. After microscopically incomplete resection, an electron boost of 10 Gy was given. The ipsilateral lymph nodes were irradiated with 50 Gy when there was extensive lymph node involvement or invasion of tumor in the axillary fat tissue. Results: The 5-year local control rate after mastectomy was 97.4% and 91.2% after breast conserving surgery. The only statistically significant risk factor for local failure was microscopically incomplete resection. The corresponding 5-year local control rates for microscopically incomplete and complete resections were 76.4% and 92.7% (p = 0.01). The risk of local relapse was increased with both marginal invasive and marginal DCIS-tissue, 86.6% of local relapses were in the same quadrant. Conclusions: High-risk patients after mastectomy and patients with breast conserving surgery achieve a high local control rate with postoperative irradiation. After microscopically incomplete resection, there is an increased risk for local relapse. (orig.)