Main Session
Sep 30
QP 13 - GU 7: Quick Pitch: Optimizing Treatment of Recurrent Prostate Cancer

1075 - Analysis on the Predictive Power of PSA-Nadir <0.1 ng/ml after Salvage Radiotherapy for PSA-Recurrence after Radical Prostatectomy - Subanalysis of the Phase-III Dose Escalation SAKK 09/10 Study and Comparison with a Retrospective Cohort

04:20pm - 04:25pm PT
Room 20/21

Presenter(s)

Thomas Wiegel, MD - University Hospital Ulm, Ulm, Baden-Wuerttembe

T. Wiegel1, S. Scharl1, S. Hayoz2, D. M. Aebersold3, D. Zips4, B. Mayer5, P. Ghadjar4, D. Böhmer4, and R. Thamm1; 1Ulm University Hospital, Clinic for Radiotherapy and Radiooncology, Ulm, Germany, 2SAKK Coordinating Center, Bern, Switzerland, 3Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland, Bern, Switzerland, 4Charité University Hospital, Department of Radiation Oncology and Radiotherapy, Berlin, Germany, 5Ulm University, Institute for Epidemiology and Medical Biometry, Ulm, Germany

Purpose/Objective(s):

Undetectable prostate-specific antigen (PSA) <0.1 ng/mL has been shown to retrospectively predict outcome following salvage radiotherapy (SRT) in patients with biochemical recurrence (BR) after radical prostatectomy (RP). The aim of study was to confirm these results in an unplanned subgroup analysis of the Phase III SAKK 09/10- trial and to compare the patient outcome with a large retrospective cohort.

Materials/Methods:

A total of 344 patients treated within the Phase III SAKK 09/10 study and 584 patients from a retrospective cohort treated with SRT (total dose 64-72 Gy, median dose 70 Gy) after RP for BR of two university centers with inclusion criteria analogous SAKK 09/10 Study are investigated. None of the patients had androgen deprivation therapy (ADT). The retrospective cohort had a slightly higher rate of pT3b/4 tumor stages (p=0.032), higher PSA before SRT (p=0.016) and higher rate of PSA persistence with a PSA before SRT 0.2-0.4 ng/ml (p=0.022). The Kaplan–Meier curves (at 5 years) and Cox regression analysis were used to evaluate the impact of PSA nadir and other disease- and treatment-related parameters on BPFS, metastasis-free survival (MFS), and overall survival (OS).

Results:

Median follow-up after SRT was 6.2 years in the cohort of SAKK patients and 5.6 years in the retrospective cohort. There was a significant difference in 5-year BPFS between patients with a PSA nadir <0.1 ng/mL (undetectable) and patients with a detectable PSA nadir after SRT in the SAKK cohort (73 % vs. 13 %, HR=4.88, 95%CI: 3.49 - 6.82; p<0.001) as well as in the retrospective cohort (78 % vs.17 %, HR=8.44; 95%CI: 5.34 - 13.45; p<0.001). Furthermore, 5-year MFS in patients with an undetectable and compared to a detectable PSA nadir was significantly superior in both cohorts with in the SAKK cohort 92 % vs. 73 % (HR=3.83, 95%CI: 2.2 - 6.64; p<0.001) and 96 % vs.85 % in the retrospective cohort (HR= 5.56; 95 %CI: 1.85 - 16.75; p=0.002). 5-year OS did not significantly differ between the groups (SAKK: 96 % vs. 93 %, p=0.582 and retrospective cohort: 97 % vs. 93 %, p=0.645).

Conclusion:

To our best knowledge, this is the first study showing the predictive value of achieving an undetectable PSA in a prospective Phase III cohort of patients. Achieving a PSA <0.1 ng/mL following SRT without ADT is a novel strong predictor of BPFS and MFS.