Abstract 429P
Background
Hypofractionated RT (5x5 Gy) with or without subsequent chemotherapy (CTx) is a standard of care used at National Institute of Oncology, Warsaw, Poland as a preoperative treatment for locally advanced rectal cancer. In order to maximize the chance of achieving complete response (CR) when surgery is not planned RT can be augmented with a simultaneous integrated boost (SIB) delivering 5x6 Gy. The aim of this report is to evaluate feasibility and safety of hypofractionated RT with a SIB in rectal cancer.
Methods
From Dec 2018 to May 2020 total 35 consecutive pts received hypofractionated RT utilizing a SIB-VMAT technique. The radiation dose fractionation was 5x5 Gy to the rectum, mesorectum and elective lymph nodes and a SIB to the GTV to a total dose of 30 Gy.
Results
17 pts (48.6%) received a SIB to the rectal tumor from which 6 pts (17.1%) were deemed unfit for surgery, 8 pts (22.9%) refused surgical treatment and 3 pts (8.6%) had an oligometastatic disease. 18 pts (51.4%) received a SIB to the clinically involved lymph nodes located outside of the standard TME field. All 35 pts completed RT as planned without interruptions or dose modifications. After a median follow-up of 92 days (range 5-435 days) there was an 8.6% (n =3) incidence of grade 2 diarrhea, 5.7% (n = 2) grade 2 proctitis, 5.7% (n = 2) grade 2 skin toxicity, 2.9% (n = 1) grade 2 cystitis, 2.9% (n = 1) grade 2 lumbosacral plexus neuropathy. 1 patient experienced grade 3 proctitis and required ambulatory treatment and 1 patient had to be hospitalized due to grade 3 diarrhea. There were no grade 2-5 hematological toxicities. Out of 21 pts who were initially qualified to receive subsequent CTx after completion of RT, 16 pts (76.2 %) received CTx without delay. In 3 cases (14.3%) CTx had to be postponed due to grade 2 proctitis (n =2) or diarrhea (n = 1). 2 pts (9.5%) were ultimately disqualified from CTx due to grade 3 toxicities (diarrhea and proctitis).
Conclusions
Hypofractionated RT with VMAT-SIB delivering a dose of 30 Gy/25 Gy/5 fractions has the acceptable toxicity profile and can be considered for patients who will not undergo surgery and for patients with involved lymph nodes located outside of the standard TME field to maximize the chance of achieving CR.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.