ESTRO 2023 - Abstract Book

S1229

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ESTRO 2023

When stratified according to the PSMA-TV (cut-off= 3 cm3), mean PSA resulted lower in the group with smaller lesions, both at the first diagnosis and at the recurrence. The time between first diagnosis and recurrence resulted longer in this group, as well, indicating a smaller burden of disease. When stratified according to the maxSUV value (cut-off= 15.7), mean PSA resulted lower in the group with lower SUVmax at the first recurrence only. Time between first diagnosis and recurrence resulted longer in this group, as well. Grouping patients according to the metastatic site, those with at least one bone metastases had mean PSA higher at the first recurrence and a shorter time between first diagnosis and recurrence. Moreover, median PSMA-TV and median SUVmax values resulted in higher in this group. Conclusion Patients with high PSMA-TV, SUVmax, and bone lesions identified at PSMA-PET are more likely to have a worse oncological outcome, confirming the importance of an optimized patient selection to identify those who could reach more favourable outcome after metastases-directed therapy. These preliminary data suggest that the definition of functional volumes in PSMA-PET (PSMA-TV) might be of clinical interest for PCa patients staging and to evaluate the response to therapy.

PO-1511 Ultrahypofractionated prostate radiotherapy: toxicty and patient reported outcomes

J. Ogg 1

1 NHS Grampian, Aberdeen Royal Infirmary, Radiotherapy Dept, Aberdeen, United Kingdom

Purpose or Objective A local evaluation of clinician reported toxicity and patient reported outcome measures of patients with low or intermediate risk prostate receiving a course of ultrahypofractionated external beam radiotherapy. Materials and Methods A total of 78 patients with low or intermediate risk prostate cancer received either ultrahypofractionated external beam radiotherapy (42.7Gy/7 fractions over 2 ½ weeks) or moderate hypo fractionated external beam radiotherapy (60Gy/20 fractions over 4 weeks). Clinician reported gastrointestinal (GI) and genitourinary (GU) toxicity was measured using RTOG grading criteria and recorded during formal clinical assessments: week 1, end of treatment, 6 weeks post treatment and 7/8 months post radiotherapy. Patient reported outcomes were recorded using the EPIC 26 short questionnaire at the start of radiotherapy, end of treatment, 6 weeks post treatment and 7/8 months post radiotherapy. Results There were generally low rates of acute GU RTOG grade 2 ≥ toxicity in both groups at 6 weeks post treatment and no statistically significant differences between ultrahypofractionated and moderate hyofractioanted radiotherapy treatment groups. (2% UHT vs 0% MHT, P=0.74). At 7/8 months late GU RTOG grade 2 ≥ toxicity remained low in both groups (2% UHT vs 3% MHT P=0.321). There was more pronounced acute GI RTOG grade 2 ≥ toxicity at 6 weeks post treatment in both treatment groups (9% UHT vs 7% MHT p=0.469). There was an increase in late GI RTOG grade 2 ≥ toxicity in the ultrahypofractionated group at 7-8 months following completion of radiotherapy although this did not reach statistical significance comapred to the moderate hypofractionated group (11% UHT vs 0% MHT,p=0.209). Patient quality of life scores remained similar across all EPIC sub domains in both the ultrahypofractionated and moderate hypofractionated groups radiotherapy groups from baseline to 7/8 months post radiotherapy. The EPIC bowel domain was the only sub domain were there was a clinically meaningful reduction from the baseline mean score at all timepoints, with the 7-8 month mean scores lower than baseline EPIC mean scores. Conclusion The acute and late clinician reported toxicity outcomes and patient reported outcomes reported confirm that external beam ultra hypofractionated prostate radiotherapy can be safely delivered with a comparable toxicity profile to moderate hypofractionated prostate radiotherapy, yet it is a more convenient option for patients and may have economic advantages for radiotherapy departments.