ESTRO 2024 - Abstract Book

S2547

Clinical - Urology

ESTRO 2024

study reports long term oncological outcomes of patients with localized prostate cancer treated with SMART in our institution.

Material/Methods:

All consecutive patients with localized and locally advanced prostate cancer treated with SMART were included in a prospective institutional database. After tumor board consensus, patients were eligible for SMART with a prostate volume ≤ 90cc, mild or moderate IPSS and MRI compatibility. Patients were classified to have low, intermediate, or high risk of recurrence based on EAU guidelines. Clinical target volume (CTV) for low risk patients consisted of the whole prostate, for intermediate and high risk categories the base of the vesicles was included. In case of seminal vesicle involvement the whole seminal vesicle was included. Treatment was performed in a two week course of 5 fractions of 7.25 Gy. Daily online plan adaptation was routinely performed to account for anatomic changes and treatment was delivered to the CTV + 3mm margin. During follow-up prostate specific antigen (PSA) levels were assessed routinely by urologists and radiation oncologists alternating conform Dutch guidelines. Biochemical recurrence was defined by Phoenix criteria (PSA nadir + 2), and local, regional or distant recurrence was established by PSMA PET-CT imaging and confirmed at a tumorboard meeting.

Results:

Between 2016-2019, 286 prostate cancer patients were treated. Patients were referred for SMART from over 35 different Dutch hospitals.

Median age was 73 years (range, 51-89), median prostate volume 40cc (range, 6-127) and IPSS scores mostly mild (50%) or moderate (40%). TUR prostate had been performed prior to treatment in 32 (11%) of patients. MRI at baseline was performed in 126 (44%) of patients, additional imaging in the form of a bone scan and PET-CT in 103 (36%) and 58 (20%), respectively. The majority of patients had high (65%) or intermediate (29%) risk for recurrence, 59 patients (21%) had PSA levels >20, 72 patients (25%) Gleason >7 and 69 patients (24%) had a ≥ cT2c tumor. Concurrent hormonal therapy was administered to 204 patients (71%), mostly for the duration of 6 (40%) or 24 (22%) months. After a median follow up of 50 months (range, 0-83) 35 local recurrences were recorded, resulting in 88% local control. Median time to local recurrence was 32 months (range, 8-76). Estimated 1-, 2-, and 5-year local control rates for the whole group were 98%, 96% and 84%, respectively. Most of the recurrences occurred in the high risk group. 5-y local control rates for low, intermediate and high risk subgroups were 100%, 89% and 81%, respectively (Fig. 1).

Tumor characteristics that significantly correlated with local recurrences were perineural growth (p=0,006), intraductal carcinoma (IDC) (p=0,001), bilateral tumor (p=0,035), Gleason score (p=<0,001) and T stage (p=0,002).

1-, 2- and 5-year overall survival rates for the whole group were 99%, 97% and 89%. Regional recurrences occurred in 31 (11%), and distant metastases in 18 (6%) patients. Median time to regional and distant recurrence was 30 (range, 8-76) and 32 (range, 13-76) months. Six patients presented with an isolated regional, and one patient with an isolated distant recurrence. 5-year regional and distant control rates for low, intermediate and high risk subgroups were 100% and 100%, 90% and 96%, 82% and 89%, respectively.