ADJUVANT RADIATION-THERAPY FOR RECTAL-CARCINOMA - PREDICTORS OF OUTCOME

Purpose: To review predictors of outcome, including sequencing of moda lities and pretreatment findings for adjuvantly treated rectal cancer. Methods and Materials: From 1975 through 1990, 307 patients with aden ocarcinoma of the rectum underwent adjuvant radiation therapy. In 251 cases the radiation therapy was administered preoperatively, either 40 -50 Gy (median dose 45 Gy) followed in 6-7 weeks by surgery (210 cases ), or 20 Gy in five fractions immediately prior to surgery (41 cases). In 56 cases, patients were referred postoperatively for radiation (me dian dose 50 Gy). Adjuvant chemotherapy was never given concurrently w ith the preoperative radiation (RT), although 43 of the cases (includi ng 14 of the preoperative RT cases) received postoperative chemotherap y. Results: Multivariate analysis (Cox model) indicated that significa nt predictors of better overall freedom from disease were preoperative rather than postoperative RT (p < 0.001), low surgical stage (p < 0.0 01), specialist surgeon (p = 0.007), low or moderate histologic grade (p = 0.026), and proximal lesion (p = 0.033). The significant predicto rs for better local control included use of preoperative RT (p < 0.001 ), low or moderate grade (p = 0.001), and low surgical stage (p = 0.01 5). The 5-year local control and freedom from disease for the preopera tive RT patients were 90% +/- 2% and 73% +/- 3%, respectively. The sel ected cases that received the short course of 20 Gy preoperatively did well. Although 24 out of 41 patients proved to have Astler Coller B2 or C disease, local control at last follow-up was 39 out of 41 (95%). A second multivariate analysis of pretreatment factors was performed o n the preoperative RT cases. The significant factors for both local co ntrol and overall freedom from disease were noncircumferential vs. cir cumferential tumor, proximal vs. distal lesion, and background of the surgeon. Additional negative factors on univariate analysis (although not achieving independent significance on multivariate analysis) inclu ded the finding of near-obstructing lesions and elevated carcinoembryo nic antigen (CEA). Grade greater than or equal to 3 sequelae occurred in 8% of cases (including 3% bowel obstruction). The only significant factor for complications was background of the surgeon (4% for colorec tal specialists vs. 12% for nonspecialists, p = 0.015). Conclusions: S ignificant factors for better tumor control included preoperative as o pposed to postoperative RT and the experience of the surgeon. In selec ted cases, excellent results can be obtained with a short course of pr eoperative radiation. Concurrent chemotherapy need not be given routin ely with preoperative radiation. Subgroups of preoperative RT cases at risk for distant metastases (who might benefit from postoperative che motherapy), and at high risk for local failure (for whom concurrent pr eoperative chemotherapy and radiation might be considered), are identi fied.