Analysis of survival and prognostic factors of clear cell adenocarcinoma of the prostate: a case–control study for a rare cancer entity

Clear cell adenocarcinoma of the prostate (CCPC) is a rare entity compared to acinar carcinoma of the prostate (APC). The survival rate and prognostic factors of CCPC are still unclear and deserve further study. We downloaded data on prostate cancer from the Surveillance, Epidemiology, and End Results database for 1975–2019. After inclusion and exclusion criteria, we compared APC and analyzed cancer-specific mortality (CSM) and overall mortality (OM) in CCPC patients and prognostic risk factors using a propensity score matching (PSM) study and multivariate Cox regression. We included 408,004 cases of APC as a control group and 130 cases of CCPC as a case group. Compared with APC patients, the incidence of CCPC was extremely low, and the median age of diagnosis was older (72.00 years vs. 69.00 years, p < 0.01). In addition, more rates were diagnosed at an earlier stage (1975–1998, 93.1% vs. 50.2%, p < 0.001), more unstaged or unknown stage ratios (87.7% vs. 42.7%, p < 0.001), and more surgical treatments (66.2% vs. 47.6%, p < 0.001), but the prognosis of CCPC patients was worse. After PSM, the median survival time of CCPC patients was shorter (57.50 month vs. 88.00 month, p < 0.01), the rate of CSM was higher (41.5% vs. 27.7%, p < 0.05), and the rate of OM was higher (99.2% vs. 90.8%, p < 0.01). In the adjusted model 2 after PSM, the CSM risk of CCPC patients reached HR 1.76 (95%CI 1.13–2.72), which was 76% higher than that of APC patients (p < 0.05). It was further found that surgical treatment might benefit CSM in CCPC patients (HR 0.39, 95%CI 0.18–0.82, p < 0.05) in Univariate analysis, but it was insignificant in further multivariate analysis. This is the first large-scale case–control report on the survival risk and prognostic factors of CCPC patients. We found that the prognosis of CCPC patients was significantly worse than that of APC. Surgery might be an effective treatment that may improve its prognosis. Clear cell adenocarcinoma, prostate, acinar carcinoma, survival rate, rare cancer, propensity score matching, case–control study.