Phase II Randomized Study of Short Course Radiotherapy Total Neo-adjuvant Therapy with or without Chlorophyllin in Reducing the Incidence of >/=Grade 2 Acute Toxicity in Advanced Rectal Cancer patients Suitable for Wait and Watch

BackgroundTotal Neoadjuvant treatment (TNT) comprising short-course radiotherapy (SCRT) and induction chemotherapy is one of the standard treatment options for locally advanced rectal cancer (LARC). The addition of localised radiotherapy boost dose using techniques such as brachytherapy can improve local tumour control and organ preservation, in selected good responder patients. Overall increased risk of acute treatment-related toxicity rates with TNT approaches can be a deterrent to compliance, treatment completion and overall outcomes. This phase II study is to evaluate, if the addition of Chlorophyllin to this approach, can reduce the burden of grade 2 or higher acute toxicity - Gastrointestinal (GI)/ Genito-urinary (GU)/ haematological toxicity and the rate of overall complete response (clinical and pathological) in well-selected wait and watch suitable locally advanced rectal cancer patients. AimsWe aim to evaluate the utility of adding chlorophyllin to SCRT-based TNT interdigitated with brachytherapy as applicable in reducing the incidence of grade 2 or higher acute GI/GU/haematological toxicity in advanced rectal cancer along with estimating the rates of complete clinical responses (pathological + clinical) at the end of two years (2-year overall complete response rates). We will be also estimating organ preservation rates, TME-free survival, Disease-free survival, Distant metastasis-free survival, Loco-regional failure-free survival, and Overall survival, along with toxicities and Quality of Life outcomes as secondary objectives. MethodsThe study is a 2-arm, phase II, prospective, randomized, double-blind, placebo-controlled superiority study evaluating the clinical outcome - local tumour response, the feasibility of non-operative management (NOM) with hypofractionated dose-escalated radiotherapy, and benefit of Chlorophyllin in reducing toxicity for total neoadjuvant treatment-TNT strategy including short-course radiotherapy and chemotherapy interdigitated with brachytherapy boost for rectal cancer patients. NOM or TME surgery will be followed based on response to NAT as standard treatment in both arms. After accrual and informed consent of eligible LARC patients, there will be: Arm 1 to receive chlorophyllin, and Arm 2 will receive a matching placebo. Permuted block randomisation with a variable block size will be used to randomize 76 (38 in each arm), providing 80% power and a two-sided alpha of 10% to test an absolute reduction in [≥]grade 2 GU/GI/Haematological toxicity rates by 30% (from 70% to 40%) with an anticipated dropout of 10%. It will also provide an estimate for NOM and organ preservation success rates. The current sample size is adequate for the estimated overall response rate at 2 years to be 50% compared to pCR of 28% (est. 95% CI: 24% - 32%) as reported in the RAPIDO study. The study started accrual on 04th July 2023 and is currently ongoing. DiscussionWe anticipate that with improved logistics of SCRT, better compliance to TNT and improved NOM rates with endorectal brachytherapy boost could be achieved with Chylorophyllin by ameliorating acute treatment-related GI/GU /Haematological toxicity rates. Improved NOM rates and lesser toxicity would result in superior QoL and improved therapeutic ratio compared to the usual high toxicity noticed in standard SCRT-based TNT strategies and TME employed globally.