Optimal Choice of Radiotherapy in Locally Advanced, Low Rectal Cancer: A Propensity Matched Analysis Comparing Short-Course Radiation With Long-Course Chemoradiation From a Tertiary Cancer Center.

Aim: To compare oncological outcomes of short-course radiation therapy (SCRT) versus long-course chemoradiation (LCRT) in patients with low rectal cancer, particularly in a high-volume center with expertise in extended total mesorectal excision (TME).

Methods: This was a single-institution, retrospective propensity-matched study using a prospectively maintained database. Patients with low rectal cancer (≤ 5 cm from the anal verge) who underwent neoadjuvant radiation (SCRT or LCRT) followed by TME between January 2014 and January 2021 were included. A 3:1 propensity score match was performed based on key clinical variables. Patients with metastatic disease or prior pelvic radiation were excluded. SCRT (25 Gy in 5 fractions) ± chemotherapy was followed by immediate or delayed surgery, while LCRT (50-50.4 Gy in 25-28 fractions) was given with capecitabine ± chemotherapy, followed by surgery. Extended resections were performed as indicated.

Results: After matching, 466 LCRT and 157 SCRT patients were analyzed. Three-year disease-free survival (DFS) was similar (62% LCRT vs. 64% SCRT, p = 0.8), with no significant differences in overall survival (OS), local recurrence-free survival (LRFS), pathological complete response (pCR: 18% vs. 20%, p = 0.5), or circumferential resection margin (CRM) positivity (6.4% vs. 10%, p = 0.12). Complication rates and local recurrence were also comparable. However, among clinical T4 tumors, SCRT was associated with significantly lower 2-year DFS (41.2% vs. 58.7%, p = 0.03) and a trend toward worse OS.

Conclusion: SCRT provides comparable oncological outcomes to LCRT in low rectal cancer when appropriately selected. However, in clinical T4 tumors, LCRT appears.