Metastases-directed radiotherapy in castration resistant oligo metastatic prostate cancer: A multicentric retrospective study from the French group COLib

Abstract

Oligometastases are defined as a number of detectable metastases less or equal to 5. In castrate-resistant oligo metastatic prostate Cancer (CR oligoM PC), Metastases-Directed Ablative radiotherapy (MDRT) is poorly investigated. Our study retrospectively reviewed the cases of CR oligoM PC treated with MDRT in 8 French high-volume radiotherapy centers. OS and PFS are defined as the delay between the first day of MDRT and death (OS) or progression according to PCWG criteria (PFS). OS and PFS are evaluated according to Kaplan Meyer, curves are compared with log rank test. Logistic regression was used to identify predictive factors for outcome: bone versus node metastasis, ISUP grade, PSA doubling Time (PSADT) at the time of MDRT, time to castration resistance. 107 patients were included in the study, among those 197 metastases received MDRT. For the overall population, the median follow-up was 25.2 months (1,4-145). OS was 93 % at 2 years and 81,4% at 3 years. At 2 years, 100 % of patients with node-only metastasis were alive versus 88,7% among those who have bone metastases (p = 0,72). The median PFS was 12,6 months (IC 95 % [9,6; 17]), with no difference among patients with node only disease versus the rest of the cohort. The PFS was 18,2 months (10,0; 32,4) in patients with PSADT >6 months versus 10,7 months (8,9; 14,3) when PSADT was inferior to 6 months. However, this difference did not reach significant. We did not find a correlation neither between ISUP grade (1-2 versus 3-4-5) and PFS, nor between hormone-sensitivity duration and PFS. Patients receiving MDRT for CR oligoM PC have a good prognosis with 81,6% OS at 3 years. PSA DT longer than 6 months could be related to better PFS. MDRT strategy could postpone the onset of new systemic treatment with median PFS >1 year.

Keywords: Ablative radiotherapy; Castrate resistant; Oligometastases; Prostate cancer; Stereotactic body radiation therapy.

Fig. 1

Progression Free Survival.

Fig. 2

Overall Survival.

Fig. 3

Progression free survival according to PSA Doubling Time. Blue curve: PSA ≤6 months; red curve PSA >6 months. P 0.11. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

We divided the population of patients developing detectable metastases at the time of castration resistance in 3 groups: group A, patients who received MDRT AND new Castration-Resistance Specific Treatment (CRST)(green group), group B who received MDRT WITHOUT CRST (pink group), and group C: those who received MDRT for CRST resistant disease (blue group). PSA variation is the change rate between pre MDRT PSA value and post MDRT PSA nadir. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)