Context: Multimodal therapy is the current recommended treatment of choice for rectal cancer. The downsizing effects of the neoadjuvant therapy/tumour regression can be assessed histologically in the resection specimen.

Aims: To assess the prognostic significance of pathological grade of tumour regression in rectal cancer treated with long course neoadjuvant therapy.

Settings and Design: This is a 5 year retrospective study conducted at a tertiary centre in South India.

Methods and Material: 137 patients with rectal adenocarcarcinoma pre-treated by long course neoadjuvant chemoradiation followed by surgery were analysed and categorised based on the Tumour Regression Grade(TRG) into 2 groups- Group 1(Good response, TRG 0,1) and Group 2 (Poor response, TRG 2,3). Other clinical and pathological features like lymphovascular/ perineural invasion, discontinuous extramural tumour deposits, resection margin status and pTNM stage of tumour were also evaluated and all variables along with TRG were correlated with disease progression and 5 year survival.

Statistical analysis used:  IBM SPSS version 20.0 software. Categorical variables expressed using frequency and percentage and the continuous variables presented using mean and standard deviation. The chi-square test was used for finding prognostic factors. Univariate analyses of survival were carried out by Kaplan-Meier method and the evaluations of differences were performed with Log Rank test.

Results: Group 1 showed reduced risk for disease progression (p 0.01) and better mean disease free period and overall survival (p 0.017 and p <0.001 respectively). Poor tumour regression was associated with lymphovascular and perineural invasion, regional lymph node metastases (p<0.001), and advanced stage of disease, and predicted an unfavourable outcome with estimated shorter mean time until disease progression.

Conclusions: Assessment of primary tumour regression is an independent prognostic predictor. The addition of lymph node status is recommended in the pathological tumour regression grading system.

Keywords: Tumour Regression Grade; rectal cancer; neoadjuvant chemoradiotherapy; pathological complete response.

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Dr Roopa Rachel Paulose

Associate Professor of Pathology, Amrita Institute of Medical Sciences and Research Centre (Amrita Vishwa Vidyapeetham), Ponnekkara P.O Kochi, Kerala 682041, India

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