Cancer-specific mortality of high-risk prostate cancer after carbon-ion radiotherapy plus long-term androgen deprivation therapy

Abstract

The treatment outcomes of patients with high-risk localized prostate cancer (PC) after carbon-ion radiotherapy (CIRT) combined with long-term androgen deprivation therapy (LTADT) were analyzed, and compared with those of other treatment modalities, focusing on PC-specific mortality (PCSM). A total of 1247 patients were enrolled in three phase II clinical trials of fixed-dose CIRT between 2000 and 2013. Excluding patients with T4 disease, 608 patients with high- or very-high-risk PC, according to the National Comprehensive Cancer Network classification system, who received CIRT with LTADT were evaluated.

The median follow-up was 88.4 months, and the 5-/10-year PCSM rates were 1.5%/4.3%, respectively. T3b disease, Gleason score of 9-10, and percentage of positive biopsy cores > 75% were associated with significantly higher PCSM on univariate and multivariate analyses. The 10-year PCSM rates of patients having all three (n=16), two (n=74), or one of these risk factors (n=217) were 27.1%, 11.6%, and 5.7%, respectively. Of the 301 patients with none of these factors, only 1 PCSM occurred over the 10-year follow-up (10-year PCSM rate, 0.3%), and significant differences were observed among the four stratified groups (p < 0.001).

CIRT combined with LTADT yielded relatively favorable treatment outcomes in patients with high-risk PC and very favorable results in patients without any of the three abovementioned factors for PCSM. Because a significant difference in PCSM among the high-risk PC patient groups was observed, new categorization and treatment intensity adjustment may be required for high-risk PC patients treated with CIRT.

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