Conclusions
An increase in the TTR cell subpopulation was protective against the risk of disease progression, and an increase in the TCM cell subpopulation was associated with the risk of death in patients with OPCa treated with mdSBRT. Disease control may be further improved by better understanding the CD8+ T-cell subpopulations and by enhancing their antitumor effect.
Purpose
This study examined the effects of metastasis-directed stereotactic body radiation therapy (mdSBRT) on CD8+ T-cell subpopulations and correlated post-mdSBRT immunophenotypic responses with clinical outcomes in patients with oligometastatic prostate cancer (OPCa).
Results
Median follow-up was 39 months (interquartile range, 34-43). Overall survival at 3 years was 78.2%. Cumulative incidence for local progression and new distant metastasis at 3 years was 16.5% and 67.6%, respectively. Between baseline and day 14 after mdSBRT, an increase in the TCM cell subpopulation was associated with the risk of death (hazard ratio, 1.22 [95% confidence interval, 1.02-1.47]; P = .033), and an increase in the TTR cell subpopulation was protective against the risk of local progression (hazard ratio, 0.80 [95% confidence interval, 0.65-0.98]; P = .032). Conclusions: An increase in the TTR cell subpopulation was protective against the risk of disease progression, and an increase in the TCM cell subpopulation was associated with the risk of death in patients with OPCa treated with mdSBRT. Disease control may be further improved by better understanding the CD8+ T-cell subpopulations and by enhancing their antitumor effect.
Trial registration
ClinicalTrials.gov NCT01777802.