Radiotherapy treatment modification for prostate cancer patients based on PSMA-PET/CT

Abstract

Background: Prostate cancer is the most common cancer among men, and its diagnosis and treatment are improving. Our study evaluated how PSMA-PET/CT prior to treatment planning might improve the optimal management of prostate cancer radiotherapy.

Methods: This retrospective pilot study included 43 prostate cancer (PCa) patients referred to our radiation oncologist department, from the urology department, for radiation therapy. 18F-PSMA-PET/CT was ordered by the radiation oncologists mainly due to the lack of resent image staging. The patients were divided into three different groups according to their initially planned treatments: radical radiation therapy (RT) (newly diagnosed PCa patients), salvage RT (patients with biochemical recurrence after radical prostatectomy), or oligometastatic RT (oligometastatic PCa patients with good response after systemic treatment).

Results: Following PSMA-PET/CT, the initially planned RT was changed for 60.5% of the patients due to new findings (metastases and/or recurrent disease). The final treatment choice was effected by PSMA-PET/CT outcome in 60.5% (26/43) of the patients, and in 50% (16/32) of patients, the radiation treatment plan changed following PSMA-PET/CT. Only 39.5% (17/43) of the patients who underwent PSMA-PET/CT were treated according to their initial treatment plans.

Conclusions: Our results indicate that PSMA-PET/CT impacts treatment decisions and the selection of RT as well as adjuvant treatment protocols in the management of prostate cancer.

Keywords: Decision-making in treatment planning; PSMA-PET/CT; Prostate cancer; Radiation therapy.

Fig. 1

Influence of PSMA-PET/CT results on initially planned treatment decisions for prostate cancer patients. Abbreviations: RT—radiotherapy, ChT—chemotherapy, ADT—androgen deprivation therapy, SBRT—stereotactic body radiation. A Groups of patients with initially planned treatment by radiation oncologist, as it was requested from the urologist. Overall, 43 PCa patients were divided into three groups according to their primary treatment plans: Radical RT group: 48.83% (n = 21) newly diagnosed PCa patients with initial treatment intention radical/curative RT. Salvage RT group: 39.53% (n = 17) PCa patients with biochemical recurrence after radical prostatectomy and initial treatment intention post prostatectomy RT and Oligometastases RT group: 11.9% (n = 5) oligometastatic PCa patients responded to systemic treatment and initial treatment intention RT to the metastases. Due to the lack of recent/present information on disease status, e.g., CT or MRI scans were performed some time ago or never, radiation oncologists initially made treatment plans; then, to confirm that they made the right decisions, they requested a PSMA-PET/CT for each patient before initiating therapy. B Changes in the primary treatment plan after PSMA-PET/CT scan results were observed in every group. In the Radical RT group (n = 21), 33.3% (7/21) proceeded with systemic treatment (ChT, ADT and/or hormonal treatment). 14 pts (14/21) were treated curatively. In 28.6% (6/21) of them, the RT plan was changed and only 38.1% (8/21) went forward as planned. In the Salvage RT group (n = 17), 47% (8/17) of the patients continued with systemic treatment ± RT. 53% (8/15) of the patients treated by RT the RT plan was changed. Only 41% (7/17) of the patients continued as planned. In the Oligometastatic RT group, the majority (60%, 3/5) underwent systemic treatment, and 20% (1/5) and 20% (1/5) of RT plans changed or remained as planned. C The patients for whom the RT plan was changed came from radical and salvage RT groups. The radical RT patients for whom the RT plan changed (n = 6), additional lymph node (LN) radiation 83.3% (5/6), and SBRT 16.6% (1/6). In the salvage RT group the RT plan change (n = 8), 62.5% (5/8) additionally received LN radiation 25% (2/8) and SBRT 37,5% (3/8), salvage RT plus boost 25% (2/8) while 12.5% (1/8) received only SBRT. D Different systemic treatments were given to patients in every group. Among the patients from the radical RT group for whom systemic therapy was added (n = 7), 57% (4/7) received ChT, 14% (1/7) received ADT, and 28.6% (2/7) received hormonal therapy (abiterone). Among the salvage RT group patients, 25% (2/8) received ChT, and the vast majority 75% (6/8) received ADT + RT. Among the oligometastatic group, 66% (2/3) received ChT, and 34% (1/3) received ADT