Vienna, Austria

ESTRO 2023

Session Item

Poster (Digital)
Outcomes comparison using PSA cut-off values of 0.1 at 6 months in high-risk prostate cancer
Abdenour Nabid, Canada


Outcomes comparison using PSA cut-off values of 0.1 at 6 months in high-risk prostate cancer

Abdenour Nabid1, Nathalie Carrier2, André-Guy Martin3, Jean-Paul Bahary4, Peter Vavassis5, Boris Bahoric6, Robert Archambault7, François Vincent8, Redouane Bettahar9, Marie Duclos10, Luis Souhami11

1Centre hospitalier universitaire de Sherbrooke, Radio-oncologie, Sherbrooke, Canada; 2Centre hospitalier universitaire de Sherbrooke, Biostatistique, Sherbrooke, Canada; 3Centre hospitalier universitaire de Québec, Radio-oncologie, Québec, Canada; 4Centre hospitalier universitaire de Montréal, Radio-oncologie, Montréal, Canada; 5Hôpital Maisonneuve-Rosemont , Radio-oncologie, Montréal, Canada; 6Hôpital Général Juif de Montréal, Radio-oncologie, Montréal, Canada; 7Hôpital de Gatineau, Radio-oncologie, Gatineau, Canada; 8Centre hospitalier régional de Trois-Rivières, Radio-oncologie, Trois-Rivières, Canada; 9Centre de santé et de services sociaux de Rimouski, Radio-oncologie, Rimouski, Canada; 10McGill University Health Centre, Radiation Oncology, Montréal, Canada; 11McGill University Health Centre, Radiation Oncolgy, Montréal, Canada

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Purpose or Objective

To determine, in patients with high-risk prostate cancer treated with 36 vs. 18 months of androgen deprivation therapy (ADT) and radiotherapy (RT), whether a PSA ≤ 0.1 ng/ml at 6 months after the beginning of ADT, is predictive of a better clinical outcome and to compare those outcomes between 36 and 18 months of ADT.

Material and Methods

We extracted data used from the PCS IV trial in which 630 patients were randomized to ADT of 36 vs. 18 months plus pelvic and prostate RT. We computed outcomes analyses only in patients who completed 18 or 36 months of ADT. Biochemical failure (BF), distant metastases (DM) and prostate cancer-specific mortality (PCSM) were analyzed with competing risks methods and overall survival (OS) and distant metastases-free survival (DMFS) rates with the Kaplan Meier method and the log-rank test.  We examined the impact of PSA ≤ 0.1 at 6 months on outcomes.


Results are reported with a median follow-up of 15.2 (IQR 13.2-18.8) years. 480/630 patients were available for the analyses. Of these, 43.8% (210) achieved a PSA ≤ 0.1 at 6 months Overall, patients with a PSA >0.1 at 6 months (56.2%) had significantly more BF (HRs (95% CI) = 2.44 (1.71-3.50), p<0.001), DM (HRs = 2.78 (1.57-4.92), p<0.001), and PCSM (HRs = 2.33 (1.30-4.17), p=0.005) than those with PSA ≤0.1. No difference was seen in OS and DMFS.

In patients receiving 36 months of ADT (167/310), 44.3% (74/167) achieved a nadir of ≤ 0.1 at 6 months compared to 43.4% (136/313) of the 97.8% (313/320) receiving 18 months.

Among patients achieving a PSA ≤0.1 at 6 months, no significant differences were seen between ADT of 36 vs 18 months in all outcomes measured. In patients with PSA > 0.1 at 6 months those receiving 18 months of ADT, compared to 36 months, developed higher rates of BF [46.3% vs. 26.9%, HRs = 2.02 (1.30-3.14), p=0.002] and DM [22% vs. 11.8%, HRs = 1.93 (0.99-3.75), p=0.054]. No significant difference was observed in PCSM, OS and DMFS between groups.


These data suggest that in high-risk patients achieving a PSA nadir ≤ 0.1 at 6 months, 18 months of ADT appears sufficient. Patients remaining with a higher PSA after 6 months of ADT may harbor a more aggressive genetic phenotype and should be considered for trials testing newer therapeutic strategies.