Organ preservation following short-course radiotherapy for rectal cancer

Background: Non-operative management of rectal cancer is increasingly being used in selected patients. Most reports include patients treated with chemoradiotherapy (CRT) before inclusion into a Watch & Wait (W&W) programme. The aim of this study was to report outcomes from a single-centre W&W programme involving a large cohort of patients. Methods: Patients treated with chemoradiotherapy (CRT) or short-course radiotherapy (SCRT) with or without chemotherapy, between 2008 and 2020, who showed signs of a clinical complete response (cCR) were reviewed. Patients were assessed using digital rectal examination, flexible endoscopy, carcinoembryonic antigen measurement, MRI, and CT imaging, discussed at the multidisciplinary tumour board meeting, and followed up in a dedicated W&W programme as from 2015. Outcomes including regrowth and 3-year survival (time to regrowth or death) were prospectively evaluated. Results: Of 142 patients who were assessed, 88 fulfilled the criteria for cCR. Treatment before cCR included CRT, SCRT with chemotherapy, and SCRT alone in 16 (18 per cent), 28 (32 per cent), and 44 (50 per cent) patients, respectively. Patients treated with CRT and SCRT with chemotherapy had more advanced clinical T- and N-stage, compared with patients treated with SCRT alone (clinical T- stage> 2: 81 per cent and 89 per cent versus 47 per cent, respectively; clinical N-stage > 0: 75 per cent and 93 per cent versus 68 per cent, respectively). Overall rate of regrowth was 19 per cent, with 31 per cent, 21 per cent, and 14 per cent following CRT, SCRT with chemotherapy, and SCRT alone, respectively. Uni- and multivariable analyses evaluating the clinical parameters revealed no statistically significant associations with risk of local regrowth. All but one patient with regrowth underwent salvage surgery. The 3-year survival rate (death with regrowth as competing risk) was 93 per cent, with no significant difference between treatment groups. Conclusion: In this cohort of W&W patients, the vast majority received SCRT with or without chemotherapy and results consistent with previous W&W reports were obtained. No statistically significant differences in terms of regrowth rate were obtained when comparing CRT, SCRT with chemotherapy, and SCRT alone. SCRT can induce sustained cCR and may precede a W&W strategy.