ESTRO 2022 - Abstract Book

S262

Abstract book

ESTRO 2022

For the first cohort, with a mean follow-up of 11.3 years (range 5-24) the last mean PSA for the non-failures were 0.14, 0.08 and 0.05 ng/ml (p<0.001) for the 3 BED groups. The percent of men with a PSA < 0.2 was 82.8, 93.1 and 96.8%, respectively. For the second cohort of patients with a benign biopsy mean age, PSA, PSAD, prostate volume (PV) and number of biopsy specimens taken were: 64.8 years, 7.6 ng/ml, 0.15, 54.6 cc and 45. Mean PSAD for the 4 percentiles ranged from 0.117-0.12 (p<0.001). The optimal PSAD (highest R 2 ) for men without prostate cancer was 0.12 ng/ml 2 (figure 1). For men receiving a partial implant to the CTV where the delivered dose had a BED of > 200 Gy (I-125 post-implant D90 > 189 Gy), the PSA contribution of the treated volume would be < 0.2 ng/ml, and the PSA contribution of the remaining benign prostate could be calculated as: pretreatment PV (cc) – CTV (cc) x 0.12. For example, the nPSA of a recent patient with a PV of 42 cc implanted with I-125 to the CTV of 18 cc which received a D90 of 205 Gy should reach (42-18) x 0.12 = 2.88 ng/ml (figure 2).

Conclusion We proposed a simple method for determining the new nadir PSA following partial gland ablation. This formula assumes the treated portion of the gland would be not produce any PSA after receiving an ablative dose of radiation. The remaining benign gland should generate a nPSA 0.12 times the untreated prostate volume. Further validation of this concept is warranted.

MO-0300 Rectal-spacer hyaluronic acid plus high-dose-rate prostate brachytherapy boost: long-term outcomes

A. Goñi Ramirez 1 , B. De Paula Carranza 1 , E. Saenz de Urturi Albisu 1 , M. Pagola Divasson 1 , M. Egiguren Bastida 1 , N. Bulto Boqué 1 , A. Ayete Andreu 1 , D.I. Ortiz de Urbina Ugarte 1 , V. Pastor Sanchis 2 , A. Bartres Salido 2 , N. Suarez 2 , M. Erzilbengoa 2 , J. Rosa Nieto 1 1 Fundación Onkologikoa - UGC Oncología Gipuzkoa, Radiation Oncology, San Sebastian, Spain; 2 Fundación Onkologikoa - UGC Oncología Gipuzkoa, Medical Physics, San Sebastian, Spain

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