Histopathological assessment of rectal carcinomas after neoadjuvant chemoradiotherapy

Background: Neoadjuvant chemoradiotherapy followed by definitive surgery has been well established as the standard treatment for patients with locally advanced rectal cancer. The aims of the study were to assess the various histopathological changes in tumor cells and stroma, to assess the tumor regression grade (TRG) and tumor downstaging after neoadjuvant chemoradiotherapy. Materials and Methods: Ninety cases of carcinoma rectum which received neoadjuvant chemoradiotherapy followed by definitive surgery were included. Pretreatment biopsy slides were assessed for tumor type and differentiation. In postsurgical specimens, pathological assessment of morphological changes, tumor downstaging, and TRG was done. Results: Out of the 90 cases in the study group, the peak incidence was in the age group of 61–70 years (35 cases, 38.9%). The male-to-female ratio was 1.25:1. Moderately differentiated adenocarcinoma was the most common histologic type on biopsy samples, accounting for 86.6% of cases. Complete disappearance of tumor cells or TRG0 was seen in 11 cases (12% of total). TRG1 was seen in 32% of cases, TRG2 in 34% of cases, and TRG3 in 22% of cases. Tumor downstaging was noted in 68% of cases. The most striking histopathological features observed were increased cytoplasmic eosinophilia (58.9%) and marked nuclear pleomorphism (78.9%). The predominant type of stromal response was fibroinflammatory type (53.3% of cases). Conclusion: Pathological evaluation remains the gold standard for assessing the tumor response to neoadjuvant therapy. Accurate assessment of therapy-induced morphologic changes and tumor downstaging is important in further treatment and prognostication of patients.