Can adjuvant pelvic radiation therapy after local excision or polypectomy for T1 and T2 rectal cancer offer an alternative option to radical surgery?

Purpose: To determine outcomes after adjuvant pelvic local radiation therapy (RT) +/- concurrent chemotherapy for T1 and T2 rectal carcinomas treated with local excision or polypectomy. Methods: We retrospectively identified adult patients with histologically proven T1 and T2 rectal adenocarcinoma, diagnosed incidentally at time of local excision or polypectomy between 01 January 2007 and 31 December 2019, and appropriately staged to confirm N0 M0 status. Patients were excluded if they had recurrent cancer or had received total mesorectal excision (TME): anterior resection (AR) or abdominoperineal resection (APR). Patient, tumour and treatment factors, together with disease and toxicity outcomes were collected from institutional medical records, correspondence and investigation reports. Descriptive statistical analyses were employed. The primary endpoint was loco-regional control and secondary endpoints were treatment-related toxicity, disease free survival, overall survival and rate of surgical salvage for pelvic recurrence. Results: The median age of the 15 eligible patients was 73 (range 49-82 years). There were 9 men (60%) and 6 women (40%). The majority had T1 disease (80%) and most had received endomucosal resection (80%). All patients received 43-52Gy (EQD2) to the primary and 43-48Gy (EQD2) to the pelvis with 46.6% receiving concurrent chemotherapy (infusional 5-FU or oral capecitabine). At median follow up of 51 months, there were no local or regional recurrences. One patient experienced an isolated distant relapse at 48 months without any locoregional recurrence. Conclusion: Our findings demonstrate good locoregional disease control with the use of adjuvant pelvic RT for T1 and T2 rectal adenocarcinoma initially treated with polypectomy or local (non-oncological) excision. These findings indicate that adjuvant pelvic RT may provide an alternative to TME surgery in patients with incidentally detected early rectal cancers.