SUO 2018: Pathologic Progression is the Dominant Driver of Conversion to Radical Therapy Post Vascular

Phoenix, Arizona (UroToday.com) Partial gland ablation or focal therapy is an increasingly attractive option for men with high volume Gleason 6 disease or low-volume Gleason 7 disease that are on the borderline for active surveillance. While early results for focal therapy studies have been promising, with moderate oncologic benefit, feasible salvage in the setting of progression and preservation of sexual and urinary function, long-term oncologic data is lacking.

CLIN1001 PCM301 is a prospective phase 3 trial which randomized 413 men with low (but not very low) risk PCa (≤3 positive cores, 3-5 mm max cancer core length) to partial gland ablation with a vascular-targeted photodynamic therapy (VTP; n=207) or active surveillance (AS; n=206). 1 Prior reports have demonstrated that men treated with VTP have had lower rates of disease progression at the primary endpoint of the trial (28% vs. 58%) and decreased conversion to radical therapy (RT) at 2 years (7% vs 33%), 3 years (14% vs 44%) and 4 years (24% vs 53%). It was also well tolerated.

The authors, in this specific abstract, focus on a sensitivity analysis looking at the triggers of conversion to radical therapy (RT), whether it was salvage surgery or radiation. Sensitivity analyses were in two steps:
  1. Censoring at time of RT subjects in both arms who converted by choice, without evidence of progression
  2. Censoring in addition those who converted after progression by PSA or volume criteria without progression in grade
Looking at the entire cohort, drivers for conversion to RT were similar in the VTP and AS arms: grade progression to GG 2 or higher (61% of 36 conversions in the VTP cohort vs 49% of 87 in the AS cohort), increase in cancer volume without change in grade (11% of VTP vs 26% of AS), PSA failure (3 consecutive PSA >10ng/mL) (0% vs 2%), and patient choice (28% vs 24%). In my eyes, this looks to favor grade progression in VTP and volume progression in AS.

Sensitivity analyses confirmed the substantially lower rate of conversion to RT in the VTP cohort when comparing only patients with objective evidence of progression (HR=0.29, 95% CI=0.18-0.45; p<0.001) and those with grade progression only (HR=0.38, 95% CI=0.23-0.64; p<0.001). The proportion of study participants in each arm who converted to RT by choice, without objective evidence of progression, was somewhat higher in the AS arm: 10 (5%) of 206 in the VTP cohort versus 19 (14%) of 207 in the AS cohort (RR=0.53, 95% CI=0.25-1.11; p=0.09).

Based on these results, the authors noted that the men who underwent VTP were less likely to progression to higher Gleason grade and/or larger volume cancer on subsequent biopsy, markedly reducing the rate of conversion to RT, with its attendant morbidity. As such, partial gland ablation with VTP can provide a clinically meaningful benefit to selected men with low-risk moderate volume GG1 prostate cancer.

Presented By: Inderbir S. Gill, USC Institute of Urology

Co-Author(s): Mark Emberton; Abdel Azzouzi; Emmanuel Coeytaux; Avigdor Scherz and Peter Scardino

Reference:

Azzouzi AR, Vincendeau S, Barret E, et al, PCM301 Study Group. Padeliporfin vascular-targeted photodynamic therapy versus active surveillance in men with low-risk prostate cancer (CLIN1001 PCM301): an open-label, phase 3, randomised controlled trial. Lancet Oncol. 2017 Feb;18(2):181-191. doi: 10.1016/S1470-2045(16)30661-1. Epub 2016 Dec 20.

Written by: Thenappan Chandrasekar, MD, Clinical Instructor, Thomas Jefferson University, @tchandra_uromd, @TjuUrology, at the 19th Annual Meeting of the Society of Urologic Oncology (SUO), November 28-30, 2018 – Phoenix, Arizona
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