ESTRO 2022

Session Item

Urology

Session Code: 6018

Session Type: Poster (digital)

Track: Clinical

Safety and feasibility of PSMA-PET guided SBRT to Oligo-Metastatic Prostate Cancer

Ahmed Gawish, Germany

Presentation Number: PO-1400

Abstract

Abstract Title:

Safety and feasibility of PSMA-PET guided SBRT to Oligo-Metastatic Prostate Cancer

Authors:

Ahmed Gawish¹, Hans-Joachim Ochel¹, Thomas B. Brunner¹

¹Medical Faculty University Hospital Magdeburg, University Clinic for Radiation Therapy, Magdeburg, Germany

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Purpose or Objective

With the increased use of PSMA-PET to direct treatment of oligorecurrent prostate cancer (ORPC) after radical prostatectomy (RP), we evaluated the results of stereotactic body or hypofractionated radiotherapy (SBRT / HFRT) for the treatment of patients with ORPC with ≤5 lesions using gallium prostate-specific membrane antigen positron emission tomography (68Ga-PSMA-PET/ CT).

Material and Methods

We enrolled patients who suffered from biochemical failure and received 68Ga-PSMA-PET/CT before SBRT (≤12 fractions)/ HFRT (>12 fractions, minimal single dose 3 Gy) without androgen-deprivation therapy (ADT). We evaluated the effect of 68Ga-PSMA-PET/CT for the planning and the progression-free survival (PFS). Treatment related toxicity was measured using Common Terminology Criteria for Adverse Events (CTCAE, v4.0). For acute and late toxicities EQD2 a/b 10 Gy and a/b 3 Gy were assumed.

Results

68Ga-PSMA-PET/CT modified the treatment in 70% of the patients. Median follow-up was 18 months (2-30 months). Of 35 patients with 42 lesions, 36% received radiotherapy only for the isolated lesion, while 64% of the patients received radiotherapy for the local regional nodal station with an EQD22 of 50 Gy with boost to the positive PSMA-LN. Mean high dose PTV -PSMA was 19 cc (range 2.54-147), mean dose was 50 Gy (30-74 Gy) in a mean of 14 fractions (6-24), High dose PTV median boost EQD22 of all patients was 72 Gy ( 52-78 Gy), EQD210 56 Gy and EQD23 67.2 (48-74,4). Non-boost median EQD2 values were 57.75 Gy, 47.25, and 54.6 Gy respectively (EQD22 , EQD210, EQD23 ). No patients suffered from recurrence in RT-field, SBRT / HFRT led to prolonged PSA decrease in 20/35 patients, however with 3 patients receiving repeated PSMA based irradiation of novel lesions during follow-up. Overall acute toxicity was low with 2 patients with reported toxicities > grade 1. Nevertheless, there was one patient with grade 4 acute toxicity and 1 patient with grade 3 toxicity, both bowels. Both were associated with large pelvic PTVs close to or at the prostatic bed. Late toxicity was ≤ grade 1 in all patients.

Conclusion

This study demonstrated the feasibility and safety of metastasis directed SBRT / HFRT to treat ORPC lesions defined by 68Ga-PSMA-PET/CT and promising results regarding intermediate-term PSA decrease were observed. Overall treatment related toxicity was well but PTVs close to RP regions should be restricted