The depth of post-treatment perirectal tissue invasion is a predictor of outcome in patients with clinical T3N1M0 rectal cancer treated with neoadjuvant chemoradiation followed by surgical resection

Background To determine if patients with clinical stage III rectal cancer treated with neoadjuvant chemoradiotherapy (CRT) and surgery have an improved survival when the response to treatment results in a pathologic T3 tumor with a microscopic focus (≤5 mm) compared with a larger (>5 mm) invasion of the perirectal tissue. Methods A retrospective review was conducted of 56 consecutive patients clinically diagnosed as T3N1M0 rectal cancer before treatment, who completed neoadjuvant CRT followed by surgical resection. Those with residual pathologic T3 disease (n = 28) were analyzed separately. Clinicopathologic data including T stage, lymph node status, k-ras status, and differentiation were reviewed. Results Among all 56 patients, there was no identified predictor of survival following neoadjuvant CRT and surgery. Among those with residual T3 disease, tumors extending >5 mm invasion into the perirectal tissue were associated with a higher risk of recurrence (50% vs 17%) and worse overall survival (4.3 vs 6.8 years, P =.015) when compared to tumors with ≤5 mm invasion into the perirectal tissue. Conclusion The depth of residual T3 tumor invasion into the perirectal tissue correlates with recurrence and overall survival in patients who underwent neoadjuvant therapy followed by surgical resection for clinically staged T3N1M0 rectal cancer.