External validation of genomic classifier based risk-stratification tool to identify candidates for adjuvant radiation therapy in patients with prostate cancer

Document Type

Conference Proceeding

Publication Date

7-2020

Publication Title

Eur Urol

Abstract

Introduction & Objectives: A genomic classifier-based risk stratification nomogram to identify candidates for adjuvant radiation therapy (aRT) after radical prostatectomy (RP) has been proposed (ref: Dalela et al. JCO). Validation study for this model is still lacking. The aim of our study was to externally validate the aforementioned nomogram using a contemporary cohort of men treated with robot-assisted RP.

Materials & Methods: A total of 350 patients who underwent RARP, (2013-2018), had adverse pathology features (positive margin,and/or pT3a/b). Genomic profile data was available for all these men. The decision and the timing to administer aRT, and androgen deprivation therapy was based on patient life expectancy, treatment expectations, and PSA kinetics. The metastasis-free survival (MFS) was estimated using the Kaplan-Meier method. The external validity of the nomogram was tested using the concordance index, calibration plot, and decision curve analysis.

Results: Median (IQR) follow-up was 26.5 (17.48-36.44) Months. 19.6% had Gleason score ≥8. Non-confined disease (pT3a/b) was noted in 67.61% of the cohort. Overall,14% (49/350) of the patients received aRT. 3.4% of the patients (12/350) developed metastasis. Overall 3-year MFS was 0.95% (95%CI: 0.92 – 0.98). The c-index of the nomogram was 0.837, with favorable calibration characteristics. DCA showed a positive net benefit for probabilities range between a 0.01 and 0.09, with the highest difference at threshold probability around 0.05. At that threshold, the net benefit is 0.06 for the model, and 0 for treating all the patients.

Conclusions: Our findings corroborate the validity of this genomic based risk-stratification tool using a contemporary cohort in identifying men who might benefit from aRT after RP. As such, it can be a useful instrument to be incorporated in shared decision making on whether or not administer aRT is worthwhile.

Volume

19

First Page

e1048

Last Page

e1049

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