Survival After Cryotherapy Versus Radiotherapy in Low and Intermediate Risk Localized Prostate Cancer

Abstract

Background: Focal therapy, including cryotherapy, reduces overtreatment in low- and intermediate-risk prostate cancer (PCa) patients with multiple comorbidities, which seems to increase in popularity compared with whole gland treatment. However, there is currently no consensus regarding the medium-term outcomes of cryosurgery as a prospective alternative to radiotherapy (RT) for such patients. Our study aims to find the available evidence that directly compares the medium-term overall survival (OS) and cancer-specific mortality (CSM) outcomes between cryotherapy and RT in patients with low- and intermediated-risk PCa.

Materials and method: Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified 47,787 patients with low- and intermediate-risk PCa diagnosed between 2004 and 2015, of which 46,853 (98%) received treatment with RT, while only 934 (2.0%) received treatment with cryotherapy. Kaplan-Meier methods were used to estimateOS and cancer-specific survival (CSS) between the 2 groups. We performed multivariable Cox regression analysis to assess overall mortality (OM), while the cumulative incidence function (CIF) was used to illustrate cancer-specific mortality (CSM) and noncancer-specific mortality (non-CSM) for all patients. Additionally, competing risks regression (Fine-Gray) was implemented to evaluate any differences. After propensity score matching (PSM), all the aforementioned analyses were repeated. After the inverse probability of treatment weighting (IPTW), we repeated Kaplan-Meier methods on OS and CSS, and performed multivariable Cox regression analysis to assess OM in cryotherapy versus RT. Sensitivity analyses were conducted by excluding patients who died of cardiovascular disease.

Results: After applying 1:4 PSM to the cryotherapy group with the RT group, the resulting RT cohort consisted of 3,736 patients who were matched with 934 patients in the cryotherapy cohort. The 5-year OS and cumulative CSM rates for PS-matched groups (N = 4670) receiving cryotherapy (N = 934) or RT (N = 3736) were 89% versus 91.8%, 0.65% versus 0.57, respectively. Multivariable Cox regression analysis demonstrated that cryotherapy was associated with a poorer OS outcome compared to RT (hazard ratio [HR] 1.29, 95% confidence interval [CI]: 1.07-1.55, p < .01). Multivariate competing risk regression analysis revealed that both treatments were not associated with CSS, with HR = 1.07 (95% CI: 0.55-2.08, p = .85). IPTW-adjusted analyses showed that the 5-years OS rates were 89.6% versus 91.8% for cryotherapy versus RT, respectively. Multivariate regression analysis for OS demonstrated that cryotherapy was more likely to have inferior OS in comparison to RT (HR = 1.30; 95%CI: 1.09-1.54; p < .01). The outcome of sensitivity analyses indicates that there was no significant difference in OS and CSS between the 2 groups.

Conclusion: For low- and intermediate-risk PCa patients treated by cryotherapy or RT, we could not demonstrate a survival difference. Cryotherapy may be a feasible option as a viable alternative to traditional radiation therapy.

Keywords: Focal therapy; Matching study; Population-based study; Survival analysis; Treatment.