Histopathological Parameters After Neoadjuvant Therapy in Rectal Tumors and Their Relationship With Treatment Response and Prognosis

Abstract

Objective: This study aimed to evaluate histopathological parameters following neoadjuvant therapy in rectal adenocarcinoma and their associations with treatment response and survival outcomes. Materials and Methods: A total of 65 patients with rectal adenocarcinoma treated with neoadjuvant chemoradiotherapy followed by surgical resection between 2007 and 2018 were retrospectively analyzed. Histopathological features, including tumor budding, poorly differentiated clusters (PDC), lymphovascular invasion (LVI), perineural invasion (PNI), circumferential resection margin (CRM) status, depth of invasion, and lymph node involvement, were re-evaluated. Tumor regression was graded using the Ryan tumor regression system and dichotomized into good (Grade 0–1) and poor (Grade 2–3) response groups. Survival analyses were performed using the Kaplan–Meier method. Results: Fourteen cases (21.5%) demonstrated a good response, whereas 51 (78.5%) showed a poor response. High tumor budding was significantly associated with reduced treatment response (p = 0.002). Perineural invasion and CRM positivity were significantly associated with worse overall survival (p = 0.001 and p = 0.014, respectively). Lymph node metastasis and greater depth of invasion showed trends toward poorer survival outcomes, although statistical significance was not reached. Patients older than 55 years had significantly longer disease-free survival (p = 0.021). Although favorable pathological response was associated with improved survival curves, this difference was not statistically significant. Conclusion: Tumor budding, perineural invasion, and CRM positivity are important prognostic indicators in rectal adenocarcinoma following neoadjuvant therapy. Comprehensive histopathological evaluation of post-treatment specimens plays a critical role in predicting treatment response and long-term outcomes.

Keywords

• Rectal cancer
• neoadjuvant chemoradiotherapy
• tumor regression grading
• tumor budding
• perineural invasion
• circumferential resection margin

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