Early outcomes of pre-operative short course radiotherapy with simultaneous integrated boost and response-adapted chemotherapy for advanced rectal cancer

Abstract

Background and purposeLimited evidence exists for dose escalation in neoadjuvant short course radiotherapy (SCRT) for rectal cancer. With enhanced imaging and radiotherapy techniques over the past decades along with the valuable endpoint of pathological complete response (pCR), we believe SCRT with simultaneous integrated boost could potentially provide deeper pathological responses and improve local control. Methods and MaterialsBetween Jan-2020 to Dec 2022, Locoregional advanced rectal cancer patients that were treated with neoadjuvant SCRT with SIB up to 5.5-6Gy per fraction with 5 daily fractions followed by response adapted chemotherapy was retrospectively reviewed. pCR rates, R0 resection rates, tumour down staging, toxicities and early pattern of recurrence are reported. ResultsAmong the 76 patients, 67 (88%) were able to undergo curative intent surgery. R0 resection was achieved in 99% (n = 66) of patients with pCR rates of 28% (n = 19). 46% (n = 31) of patients had significant pathological down staging (ypT2N0) and 55% (n = 37) of patients had both T and N down staging. Most common grade 3 or above radiotherapy related side effects were proctitis, rectal pain and dermatitis found in 5% (n = 4), 3% (n = 2) and 3% (n = 2) of patients respectively. Grade 3 or above surgical complications were observed in 15% (n = 10) of patients. There was no treatment related deaths. With a median follow up of 27 months, only 6% (n = 4) had local recurrence after surgery. ConclusionNeoadjuvant short course radiotherapy with simultaneous boost for rectal cancer is feasible with no added toxicities. Patients who underwent surgery achieve a high R0 resection and pCR rates. Early data suggests low rates of locoregional recurrence. Further follow up and research is needed to validate and optimize the dose, method, and schedule of dose escalation.