Aim: To assess the toxicity differences between neo adjuvant and adjuvant chemo radiation in carcinoma rectum. Materials and Methods: Patients who underwent neoadjuvant or adjuvant chemoradiation for carcinoma rectum were enrolled into study. The total number of patients 30 (neoadjuvant 15+ adjuvant 15). All patients with histopathological diagnosis of carcinoma rectum. Adenocarcinoma of rectum. Patients belonging to M0 (without metastasis. Results: Majority of the patients in this study were males in both neoadjuvant (80%) and adjuvant arms (73.3%) Majority of tumours in neoadjuvant arm were in lower rectum and majority of tumours in adjuvant arm were in upper & lower rectum. Both neoadjuvant and adjuvant arm were of moderately differentiated adenocarcinoma histology. Majority of patients (except four patients) had pathological node positive disease. The difference in yield of lymphnodes between the groups were statistically significant as assessed by two tailed t test P = 0.023. Similarly number of positive lymphnodes were more in patients who underwent surgery first (mean ± SEM = 6.33 ± 2.12) compared those who underwent neoadjuvant concurrent chemo radiotherapy and then underwent surgery (mean ± SEM = 0.28± 0.28), the difference is statistically significant P <0.0001. In neoadjuvant arm one patient had perineural invasion & one patient had lymphovascular invasion, where as in adjuvant arm none of the patients had perineural invasion but one patient had lymphovascular invasion. in neoadjuvant arm majority of patients had pathological T1 status, where as in adjuvant arm majority of patients had pathological T3 status. In neoadjuvant arm most of the patients had pathologically node negative status, where as in adjuvant arm 5 patients had pN2b, 4 patients had pN0, 2 patients had pN1a and 2 patients had pN2a. In the neoadjuvant arm only one patient had pathological positive lymphnodes. In neoadjuvant arm majority of patients had pathological T2 status, where as in adjuvant arm majority of patients had pathological T3 status. In neoadjuvant arm most of the patients had pathological node negative status, where as in adjuvant arm 5patients had pN2b, 4patients had pN0, 2 patients had pN1 and 2 patients had pN2a. In neoadjuvant arm most of the patients were pathological stage 0, I & IIA, where as in adjuvant arm most of the patients were pathological stage IIIB & IIIC. In neoadjuvant arm most of the patients were pathological stage IIA, I and 0, where as in adjuvant arm most of the patients were pathological stage IIIC & IIIB. 3 patients had complete response and 12 patients had partial response. Conclusion: Pathologic response (p CR& p PR) in patients who underwent Neoadjuvant chemo radiotherapy arm was good. Chemo radiotherapy down staged the tumour in all patients in the neoadjuvant arm. Haematological toxicities were more pronounced in Neoadjuvant arm, while Gastrointestinal and Genitourinary toxicities were more in Adjuvant arm.

Keywords: Colorectal Cancer; Neoadjuvant Chemo Radiotherapy; Haematological Toxicities.