Prognostic significance of the mEPE score in intermediate-risk prostate cancer patients undergoing ultrahypofractionated robotic SBRT

TL;DR

This study shows that a high mEPE score in intermediate-risk prostate cancer patients is linked to a higher chance of treatment failure after robotic SBRT.

Contribution

The study identifies the mEPE score as a strong predictor of biochemical failure in prostate cancer patients treated with ultrahypofractionated SBRT.

Findings

A high mEPE score of 5 was strongly associated with lower biochemical failure-free survival.

Higher radiation doses (36.25 Gy vs. 35 Gy) were linked to better outcomes.

A PSA nadir above 1 ng/ml was also associated with lower survival rates.

Abstract

This study aimed to evaluate the prognostic significance of magnetic resonance imaging (MRI) parameters on biochemical failure-free survival (BFS) in patients diagnosed with intermediate-risk prostate cancer and treated with robotic ultrahypofractionated stereotactic body radiotherapy (SBRT) without androgen deprivation therapy (ADT).

A retrospective analysis was conducted in patients with intermediate-risk prostate cancer undergoing robotic SBRT delivered in five fractions with a total radiation dose of 35–36.25 Gy. The primary endpoint was biochemical failure as defined by the Phoenix criteria. Among other clinicopathological data, T stage, Prostate Imaging-Reporting and Data System (PI-RADS) score, and multiparametric magnetic resonance imaging-based extra-prostatic extension (mEPE) score were collected and analyzed using the log-rank test.

A total of 74 patients were eligible for analysis. Median age at treatment was 68.8 years and median prostate volume was 47.8 cm3. Fifty-four and 14 patients were diagnosed with Gleason scores 7a and 7b, respectively. In total, 40 patients were classified as having unfavorable intermediate-risk prostate cancer according to American Urological Association/American Society for Radiation Oncology/ Society of Urologic Oncology (AUA/ASTRO/SUO) guidelines. The median follow-up was 30 months (range: 4–91.2 months; interquartile range (IQR): 18.5–48 months). The 3‑year BFS was 92%. A total of 12 (16.2%) biochemical failures were reported. In univariate analysis, an mEPE score of 5, the delivered total radiation dose (35 Gy vs. 36.25 Gy), and a prostate-specific antigen (PSA) nadir >1 ng/ml were associated with lower BFS (mEPE–BFS: p < 0.001, total radiation dose–BFS: p = 0.04, PSA nadir–BFS: p =< 0.001).

Patients diagnosed with intermediate-risk prostate cancer with a high mEPE score are more likely to experience biochemical failure after SBRT. Treatment intensification measures, such as administration of concomitant ADT, should be considered.

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