ESTRO 2024 - Abstract Book

S33

Invited Speaker

ESTRO 2024

Sunnybrook Health Sciences Centre, Radiation Oncology, Toronto, Canada

Abstract:

For intermediate and high risk disease where the only the prostate (+/- proximal seminal vesicles) are being treated, EBRT options include conventional (e.g. 78Gy in 39 fractions – 78/39), moderate (60/20) or ultrahypofractionation schedules (40/5). For high risk disease where elective pelvic radiation is being delivered, conventional (46/23) or moderate hypofractionation schedules (48/25) are commonly used. In patients getting an HDR or LDR brachytherapy boost, mini-pelvic doses of 37.5/15 fractions or whole pelvic doses of 46/23 fractions are standard. For patients with de novo oligometastatic disease, a moderate (55/20 fractions) or ultrahypofractionated prescription (36/6 fractions) is standard. For conventionally fractionated EBRT, a microboost (95/37 fractions) may be used but its role in moderate and ultrahypofractionated schedules is still under study. The following trials are being followed with interest. For intermediate risk patients, PACE-C has completed accrual of 1208 patients, comparing 40/5 vs 60/20. There are 3 phase 2 and one phase 3 randomized studies of 2 vs 5 fractions: iSMART will randomize 144 pts on standard LINAC to 40/5 vs 27/2 (with immobilization), FORT will randomize 136 patients on MRL to 37.5/5 vs 25/2 and HERMES will randomize 46 patients on MRL to 36.25/5 vs 24/2 + microboost 27/2. SABR-DUAL will randomize 562 patients on MRL to 40/5 vs 27/2. For high risk patients the following studies are accruing or close to activation. PACE-NODES: 40/5 prostate +/- 25/5 pelvis, n=536; PRIME: MHRT (68/25 prostate, 50/25 pelvis) vs UHRT (35/5 prostate, 25/5 pelvis), n=434; High Five Trial (NRG GU013): CFRT (83/45) or MHRT (60/20) vs UHRT (40/5 +/- 25/5 pelvis +/- microboost), n=1209; ASCENDE-SBRT (CCTG PR.24): 46/23 fractions + brachytherapy boost vs 40/5 prostate + 25/5 pelvis, n=710.

3329

Emerging perspectives on intestinal stem cell regeneration through single-cell and spatial analysis

Ioannis Verginadis

University of Pennsylvania, Radiation Oncology, Philadelphia, USA

Abstract:

Radiation therapy (RT) is an established treatment modality and is recommended for about half of all cancer patients. Nevertheless, despite its therapeutic efficacy, the effective dose of radiation is restricted due to the harmful effects of unintentional exposure of the intestine during the treatment of abdominal or pelvic cancers. About 20% of the patients undergoing abdominal or pelvic RT have their treatment plans modified due to these adverse effects, which may compromise local tumor control. Despite advancements in technology aimed at reducing radiation exposure to normal tissues, radiation-induced toxicity to normal tissues remains a significant challenge in treating cancer patients with localized disease. Most of the research on intestinal epithelial regeneration post-IR originates from studies utilizing large radiation fields, such as those employed in whole abdominal or total body IR. Thus, there are no existing models which investigate the local regenerative response to radiation-induced intestinal damage within the same biological sample. Our group has developed a clinically relevant mouse model, wherein a minimally invasive surgery is performed to implant a bismuth subcarbonate radiopaque marker onto the surface of the jejunum. Using Cone-Beam CT, we image the mice and administer focal IR of 18 Gy (using a 5x5mm collimator) with the radiopaque marker