ESTRO 2024 - Abstract Book

S2635

Clinical - Urology

ESTRO 2024

prognostic factors in question. Sub-group analysis was then performed by margin status to investigate the potential difference in nature of recurrence in this patient population.

Results:

Median values for age at treatment was 65 years and SRT dose was 70.2 Gy. Median time from prostatectomy to SRT was 21.5 months and median follow-up after SRT was 8.5 years. On multivariate analysis of the entire cohort we found higher risk of BCR in patients with pre-SRT PSA > 0.2 ng/mL (HR 1.96; 95% CI 1.24-3.11), increasing T stage (HR 1.38; 1.07-1.78), and GS (HR 1.57; 1.20-2.05) while positive margins were predictive of decreased risk of BCR post SRT (HR 0.63; 0.41-0.98). When grouped by margin status patients with positive margins maintained these trends (Table 1). In patients with negative margins we found that pre-SRT PSA, T stage, and GS were no longer significant, only PLNRT was correlated with risk of BCR.

Table 1: Cox regression for predictors of BCR by margins

Covariates

Hazard Ratio

95% CI

p value

Positive Margins

T Stage

2.312

1.360-3.931

0.002

Gleason Score

1.770

1.126-2.783

0.013

PLNRT

0.887

0.415-1.894

0.757

PSA > 0.2 ng/mL

4.300

1.985-9.315

0.001

ADT

0.451

0.196-1.041

0.062

Negative Margins

T Stage

1.012

0.733-1.397

0.942

Gleason Score

1.344

0.953-1.897

0.092

PLNRT

0.477

0.229-0.995

0.048

PSA > 0.2 ng/mL

1.078

0.597-1.947

0.803

ADT

0.800

0.353-1.815

0.594

Conclusion:

We report favorable prognosis in patients with pathologically positive margins following post-prostatectomy SRT. In fact, PLNRT provided no apparent added benefit likely because these patients are more likely to have isolated prostate bed disease. In contrast, patients with negative margins benefited significantly with the addition of PLNRT indicating a higher likelihood of having disease outside of the prostate bed. Our data suggest that the benefit of PLNRT is significant in these patients and should be considered in this setting regardless of other risk factors.