ESTRO 2023 - Abstract Book

S1235

Digital Posters

ESTRO 2023

23 patients were selectionated and patients were divided in differents groups according PTV (<30, 30-60, >60) volumen and BED (60Gy) (using an α / β of 10 Gy).

The main outcomes were local control (LC) and overall survival (OS). LC was assessed by computed tomography and PET.

Results 19 patients with adrenal metastases were included (4 patients not started SBRT) and 15 were men. In all of them, an internal target volumme (ITV) was generated base on 4D-TC. The planing target volumen (PTV) was created by adding 3 or 5mm to ITV. At least 98& of the PTV received 98& of prescribed dose. Treatment was delivered in alternate days. Mean age was 59 (42-78) years. Lung cancer metastases represents 73,8%.The Karnosky Performance Status was 80-100% in all cases. Adrenal metastases doses were 24 Gy in 3 fractions (in one patient), 27 Gy in 3 fractions and 35 Gy in 5 fractions (in 2 patients), 40 Gy in 5 fractions (in 5 patients) and 45 Gy in 5 fractions (in 9 patients). Mean PTV volumen was 42,2 (165,1-16.9) and mean dose was 40Gy (24-45) in 5 fractions (3-5). Mean follow-up was 18,5 months with a mean OS of 16,5 (2-54)months. Local control rate was 94.9% with a complete response of 68,4%. Median OS in BED<60Gy was 16 months and 18,2 months in BED>60Gy. Median LC was similar in boths groups, 12,4 vs 12,7 months. Median LC in PTV<30 was 15,2, 30-60 was 13 months and in >60 was 7,3 months (p=0.79) Median OS in PTV<30 and 30-60 was 19 months vs 10,3 in PTV<60. No toxicities grade 2 or higher were reported. Conclusion Helical-Tomotherapy-SBRT is accuraten, feasible and well tolerated treatment for adrenal metastases. High dose SBRT (BED10Gy >60) and PTV <60cc provides better overall survival than low dose SBRT. No significant differences have been found for local control but smaller PTV provides higher local control. A. Castelluccia 1 , G. Grimaldi 2 , D. Marchesano 3 , I. Annessi 4 , F. Bianciardi 3 , A. Dipalma 3 , C. Borrazzo 3 , M. Rago 3 , M. Masi 3 , R. El Gawary 3 , M. Valentino 3 , L. Verna 3 , P. Gentile 3 1 "A. Perrino" Hospital, Department of Radiotherapy, Brindisi, Italy; 2 San Pietro FBF Hospital, Department of Radiotherapy, Rome, Italy; 3 San Pietro FBF Hospital, Radiotherapy, Rome, Italy; 4 San Pietro FBF, Radiotherapy, Rome, Italy Purpose or Objective Stereotactic MR-guided Adaptive RT (SMART) seems suitable to treat local recurrences of prostate cancer, due to precise tumor volume delineation favorited to good soft tissue contrast and the opportunity to reduce treatment volumes using daily on-line adaptation of RT plan, without the need of invasive fiducials placement. The purpose of this study was to assess tolerance and to investigate a possible dosimetric correlation of toxicity in patients undergoing SMART for local recurrence of prostate cancer either in post-operative and post-irradiation setting. Materials and Methods After clinical assessment with F18Choline PET-TC and multiparametric MR, patients with histological proven diagnosis of recurrence of prostatic cancer underwent SBRT using MR-hybrid LINAC system (MRIdian, Viewray), without fiducial markers or spacer OAR. The dose prescription was 35 Gy (7 Gy/fr) and 40Gy (8Gy/fr) for post-irradiation and post-operative setting, respectively, at 80% isodose, delivered on 5 days (3fr/week). An isotropic 3mm-margin was created around the lesion for the PTV. SMART consisted of identification of target and OARs on pre-treatment and daily MR images, with on-line calculation and delivery of a new plan for every fractions because of inter-fraction variation of bladder and rectal filling. Common Terminology Criteria for Adverse Events v.5 was used to score gastrointestinal and genitourinary toxicity during follow-up. Results Between 2019 and 2022, 22 patients treated with SMART for prostatatic local relapse were retrospectively evaluated. The median Gleason Score at biopsy prior SMART was 8 (range, 6-9). About the site of relapse, 7 recurrences were intraprostatic and 15 were lesions into prostatic bed. 50% of patients were previously irradiated (median dose 76 Gy, range 70-80), 1 patient received postoperative RT before SMART and 1 patient received 2 radiation treatments before SMART. The median interval between primary treatment and SMART was 8 years from the first radiation treatment and 3 years from surgery. ADT was associated to SMART for 4 castration resistant patients. The median pre-SMART PSA level was 3.4 ng/mL (range 1.1–5). The baseline patients’ and treatments characteristics are described in Table 1. At a median follow-up of 10 months (range 2-36), the median PSA level was 0 ng/mL (range, 0-1.08). Acute tolerance was excellent, with no grade ≥ 2 GI toxicity and no grade >2 treatment-related GU toxicity recorded. The highest toxicity, consisting of moderate urinary urgency and frequency, occurred in 1 reirradiated patient, which received the highest dose to urethra (Dmax 41.7Gy). No other dosimetric correlations were found. No difference in terms of acute toxicity between postoperative SMART group and re-irradiation group was recorded. PO-1519 Stereotactic adaptive MR-guided RT: post-operative RT and re-irradiation for prostate local relapse