Early Toxicity and Complete Pathological Response Assessment in Rectal Cancer Patients Receiving Short Course Versus Long Course Radiotherapy

Abstract

Background: Neoadjuvant radiotherapy (RT) is essential in rectal cancer treatment, with short-course (SCRT) and long-course (LCRT) approaches widely used. SCRT provides a shorter treatment duration, whereas LCRT allows for better tumor downstaging but extends treatment time. The impact of these strategies on early toxicity and complete pathological response (pCR) remains a key concern. This study evaluates and compares these outcomes to guide optimal treatment selection. Methods: This prospective cohort study included 66 rectal cancer patients at Mostafa Kamel Hospital’s Radiation Oncology Center. Patients were assigned to SCRT (n=33) or LCRT (n=33) based on treatment protocols. Data on early toxicity and pathological response were collected using structured sheets, postoperative pathology reports, and Common Terminology Criteria for Adverse Events (CTCAE v5.0). Results: SCRT was associated with a significantly higher complete response rate (OR = 2.45, 95% CI [1.12–5.36], p=0.025) compared to LCRT. LCRT had higher rates of radiation-induced toxicities, including proctitis (OR = 15.2, p<0.001) and hand-foot syndrome (OR = 12.5, p<0.001), whereas SCRT demonstrated a more favorable toxicity profile. Hematologic toxicity showed no significant differences, but patients with multiple comorbidities had an increased risk of treatment-related adverse events (OR = 1.88, p=0.033). Conclusion: These findings support SCRT as a viable option for rectal cancer treatment due to its superior pCR rates and lower toxicity burden compared to LCRT. Future research should focus on long-term oncologic outcomes, late toxicity, and patient-reported quality of life to refine treatment decisions.