Purpose: The results of therapy for 103 patients with locally advanced colon cancer who received radiotherapy were analyzed to determine the outcome and tolerance of therapy.
Methods and materials: Between 1974 and 1994, 103 patients received radiotherapy and maximal resection of locally advanced colon cancers. Following resection, 50 patients had no residual disease, 18 patients had microscopic residual disease, and 35 patients had gross residual disease. External beam radiotherapy was initiated 1 to 4 months following resection except in two patients who received preoperative radiotherapy. Treatment was delivered to the tumor bed and adjacent lymph nodes using 4 to 18 MV X-rays with doses ranging from 16.2 to 60 Gy. Intraoperative electron radiotherapy (IOERT) was also administered to 11 of the patients with doses ranging from 10 to 20 Gy. Chemotherapy was administered to 77 patients. Follow-up in survivors ranged from 0.5 to 17 years (median: 5.8 years).
Results: The 5-year actuarial local failure rate was 10% for patients with no residual disease, 54% for patients with microscopic residual disease, and 79% for patients with gross residual disease (p < 0.0001). For patients with residual disease, local failure occurred in 11% of patients receiving IOERT compared with 82% of patients receiving only external beam therapy (p = 0.02). The 5-year actuarial survival rate was 66% for patients with no residual disease, 47% for patients with microscopic residual disease, and 23% for patients with gross residual disease (p = 0.0009). The 5-year survival rate in patients with residual disease was 76% for patients receiving IOERT and 26% for patients receiving external beam therapy alone (p = 0.04).
Conclusions: Patients with locally advanced colon cancer who have had a complete resection have a high probability of local control after external beam irradiation +/- 5 fluorouracil (5FU)-based systemic therapy. The toxicity of therapy can be minimized with attention to treatment technique and dose. Local control and survival rates in patients with residual disease who received IOERT appear to be significantly greater than for those patients who received external beam radiotherapy therapy alone.