ESTRO 2022 - Abstract Book

S442

Abstract book

ESTRO 2022

M. Verweij 1,2 , S. Hoendervangers 1,2,3 , L. von Hebel 4 , A. Pronk 5 , A. Schiphorst 5 , E. Consten 6,7 , E. Verdaasdonk 3 , T. Rozema 8 , L. Verkooijen 9 , H. van Grevenstijn 2 , M. Intven 1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands; 2 UMC Utrecht, Surgery, Utrecht, The Netherlands; 3 Jeroen Bosch Hospital, Surgery, Den Bosch, The Netherlands; 4 UMC Utrecht, Radiotherapy, UMC Utrecht, The Netherlands; 5 Diakonessenhuis, Surgery, Utrecht, The Netherlands; 6 Meander Medical Centre, Surgery, Amersfoort, The Netherlands; 7 UMC Groningen, Surgery, Groningen, The Netherlands; 8 Institute Verbeeten, Radiotherapy, Tilburg, The Netherlands; 9 UMC Utrecht, Imaging & Oncology, Utrecht, The Netherlands Purpose or Objective Prolonging the interval between short course radiotherapy (SCRT) and total mesorectal excision (TME) for rectal cancer increases tumor downsizing and the probability of organ-preservation. A prolonged interval has been reported to decrease postoperative complications compared to immediate surgery. It might however increase radiation-induced toxicity. This study systematically evaluated patient-reported bowel dysfunction and physician-reported radiation toxicity during a prolonged interval between SCRT and TME for rectal cancer. Materials and Methods Consecutive patients treated with SCRT and prolonged interval (> 4 weeks) to TME for intermediate risk rectal cancer (T1- 3(MRF-)N1M0 or T3(MRF-)N0M0), locally advanced rectal cancer (LARC; T3-4(CRM+)N0-2M0 or T1-4N2M0) and contra- indication for chemoradiation, or M1 rectal cancer were included. Repeated measurements of patient-reported bowel dysfunction (measured by the low anterior resection syndrome (LARS)-score) and physician-reported toxicity (diarrhea, fatigue, cystitis non-infective, dermatitis and urine-incontinence according to CTCAE) were done before start of SCRT (baseline), at completion of SCRT and (bi-)weekly until TME or 8 weeks after completion of SCRT. Results Fifty-one patients were included, of whom 31 (61%) were male and the median age was 67 (range: 44-91). The indication for SCRT with prolonged interval to TME was intermediate risk in 32 (63%), LARC in 5 (10%) and M1 in 14 (28%) patients. Median interval to TME was 68 days (IQR 52-93). Both patient-reported bowel dysfunction and physician-reported radiation toxicity peaked at week 1-2 after completion of SCRT and gradually declined thereafter. Thirty-seven (79%) patients self-reported major bowel dysfunction at week 2 after completion of SCRT, declining to 8 (25%) patients at week 8. Physicians reported diarrhea grade 1-3 in 35 (74%) patients at week 2 (of whom 11 (23%) grade 3), declining to 9 (27%) grade 1-2 at week 8. One patient had his TME scheduled earlier due to persisting grade 3 diarrhea. Physicians reported fatigue grade 1-2 in 30 (64%) patients at week 2, cystitis grade 1-2 in 19 (43%) patients at week 1, dermatitis grade 1 in 8 (18%) patients at week 1 and urine-incontinence grade 1 in 2 (7%) patients at baseline.

Conclusion No grade 4-5 radiation toxicity occurred during a prolonged interval between SCRT and TME for rectal cancer. Patient- reported major bowel dysfunction and physician-reported grade 1-3 diarrhea, grade 1-2 fatigue, grade 1 cystitis and grade 1 dermatitis were prevalent during 1-2 weeks after SCRT and gradually restored thereafter. Patients reported major bowel dysfunction with a higher incidence than physicians reported diarrhea.

PD-0494 Secondary dosimetric analysis of a phase II study on radiation volume de-escalation in rectal cancer

G. D'Ercole 1 , M. Fiore 1 , R. Alaimo 1 , P. Trecca 1 , G.M. Petrianni 1 , L.E. Trodella 1 , M. Marrocco 1 , C. Greco 1 , E. Ippolito 1 , S. Ramella 1