Event-free survival after 68 Ga-PSMA-11 PET/CT in recurrent hormone-sensitive prostate cancer (HSPC) patients eligible for salvage therapy

Abstract

Background/aim: Prostate-specific-membrane-antigen/positron emission tomography (PSMA-PET) detects with high accuracy disease-recurrence, leading to changes in the management of biochemically-recurrent (BCR) prostate cancer (PCa). However, data regarding the oncological outcomes of patients who performed PSMA-PET are needed. The aim of this study was to evaluate the incidence of clinically relevant events during follow-up in patients who performed PSMA-PET for BCR after radical treatment.

Materials and methods: This analysis included consecutive, hormone-sensitive, hormone-free, recurrent PCa patients (HSPC) enrolled through a prospective study. All patients were eligible for salvage therapy, having at least 24 months of follow-up after PSMA-PET. The primary endpoint was the Event-Free Survival (EFS), defined as the time between the PSMA-PET and the date of event/last follow-up. The Kaplan-Meier method was used to estimate the EFS curves. EFS was also investigated by Cox proportional hazards regression. Events were defined as death, radiological progression, or PSA recurrence after therapy.

Results: One-hundred and seventy-six (n = 176) patients were analyzed (median PSA 0.62 [IQR: 0.43-1.00] ng/mL; median follow-up of 35.4 [IQR: 26.5-40.3] months). The EFS was 78.8% at 1 year, 65.2% (2 years), and 52.2% (3 years). Patients experiencing events during study follow-up had a significantly higher median PSA (0.81 [IQR: 0.53-1.28] vs 0.51 [IQR: 0.36-0.80] ng/mL) and a lower PSA doubling time (PSAdt) (5.4 [IQR: 3.7-11.6] vs 12.7 [IQR: 6.6-24.3] months) (p < 0.001) compared to event-free patients. The Kaplan-Meier curves showed that PSA > 0.5 ng/mL, PSAdt ≤ 6 months, and a positive PSMA-PET result were associated with a higher event rate (p < 0.01). No significant differences of event rates were observed in patients who received changes in therapy management after PSMA-PET vs. patients who did not receive therapy changes. Finally, PSA > 0.5 ng/mL and PSAdt ≤ 6 months were statistically significant event-predictors in multivariate model (p < 0.001).

Conclusion: Low PSA and long PSAdt were significant predictors of longer EFS. A lower incidence of events was observed in patients having negative PSMA-PET, since longer EFS was significantly more probable in case of a negative scan.

Keywords: Event-free survival; Hormone-sensitive prostate cancer; PSMA PET; Prostate cancer; Prostate cancer survival.

Fig. 1

Study profile

Fig. 2

Rates of positivity for PSMA-PET in a population of biochemically recurrent HSPC patients, prospectively enrolled. The rates of positivity have been reported for pelvic vs systemic recurrence, and for oligo-metastatic (up to 3 lesions) vs multimetastatic disease. Data have been reported for the overall population and stratified by clinical setting

Fig. 3

EFS for the overall population

Fig. 4

a–d EFS stratified by potential predictors PSA at PET scan, PSAdt, PET results, and change of management

Fig. 4

a–d EFS stratified by potential predictors PSA at PET scan, PSAdt, PET results, and change of management