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SBRT represents a low-toxicity treatment for prostate cancer localizations that may allow delaying the start of androgen deprivation therapy (ADT) in the oligometastatic setting. In the RADIOSA phase II randomized trial (NCT03940235), the biology task entails the identification of predictive and prognostic biomarkers in the context of oligorecurrent, castration-sensitive PCa in order to distinguish polymetastatic from oligometastatic disease. This may lay the groundwork for personalized treatments for those patients who could really benefit from metastases-directed therapies.

According to the administration of ADT and the location of the metastases, patients who matched the inclusion criteria were divided into two treatment groups: SBRT only on all lesions (arm A) vs  SBRT on all lesions + 6 months ADT (arm B). Common serum-derived biomarkers were collected at baseline and at 3 months after RT. The prognostic nutritional index, an immune and nutrition-based prognostic score, and the controlling nutritional status (CONUT) score, a scoring system for evaluating patient’s nutritional status, were calculated in accordance with the body of available literature. As inflammatory indicators, neutrophil-lymphocyte ratio (NLR) and the NLR-albumin ratio (NLRAR) were assessed. Changes in these parameters between baseline and the 3-months timepoint were evaluated both in absolute and relative values. Significant differences in the trend of these parameters were assessed using the non-parametric Wilcoxon rank-sum test by grouping patients according to ADT administration (arm B vs A, yes vs no) and site of metastases (bone versus lymph node).

The current analysis comprised 82 patients (41 arm A SBRT only, 40 arm B, SBRT+ADT). When patients were stratified by ADT administration (Fig1), cholesterol values showed an increasing trend in the group receiving ADT (p < .001), and the change in albumin level was also different between the two groups (p < .05). When patients were stratified by site of metastases (52 lymph nodal, 29 bone localizations) (Fig2), the values of NLR and NLRAR were found to be increased in patients with bone localizations (p < .05).

The addition of ADT appears to have an impact on changes in cholesterol and albumin, two markers of a deteriorating quality of life. Additionally, it appears that the site of metastases and inflammatory status are associated. As bone localizations are linked to a lower response rate than lymph node-only sites, this outcome is consistent with the well-known fact that a higher inflammatory status results in a worse prognosis. The examined parameters seem to represent intriguing candidates for possible use in clinical decision-making to group patients according to whether they would benefit more from less aggressive therapies. The validation of these potential biomarkers requires further evaluations, correlations with clinical outcomes and extended follow-up data.