Wysock JS, Rapoport E, Hernandez H, Gogaj R, Lepor H. Biopsy assessment of oncologic control 3 years following primary partial gland cryoablation: a prospective cohort study of men with intermediate-risk prostate cancer. J Urol. 2023;210(3):454-464.

Study Need and Importance

There is increasing adoption of focal therapy (FT) for managing select cases of prostate cancer. We have a 10-year experience using a multitude of ablative energy sources and prefer cryoablation due to superior delivery of confluent cytotoxic energy to a predefined treatment zone. There is a paucity of FT studies performing protocol biopsies at predetermined intervals beyond the first year of treatment. The ultimate role of FT awaits compelling evidence demonstrating intermediate- and long-term oncologic disease control. The present study reports disease recurrence following primary partial gland cryoablation for men with intermediate-risk disease enrolled in an institutional review board-approved prospective outcomes registry undergoing protocol biopsies during the third year after treatment.

What We Found

Our oncologic assessment stipulated protocol biopsy of the pretreatment MRI lesion, any new MRI lesion, and 12-core random systematic biopsy in all subjects during the third year of follow-up. At 36 months, model-estimated rates of freedom from recurrence of in-field, out-of-field, and overall clinically significant cancer were 97% (95% CI: 92-100), 87% (95% CI: 80-94), and 86% (95% CI: 78-93), respectively (see Figure). The model-estimated proportion with freedom from failure at 36 months was 97% (95% CI: 93-100).

Figure 1. Nonparametric maximum likelihood estimators for freedom from in-field recurrence (A), freedom from out-of-field recurrence (B), freedom from any recurrence (C), and freedom from failure of treatment (D). Recurrence was defined as Gleason grade group ≥2 cancer on biopsy, and failure of treatment was defined as whole-gland salvage treatment, metastatic prostate cancer, or prostate cancer mortality. Solid lines indicate nonparametric maximum likelihood estimators. Gray rectangles represent regions of nonunique nonparametric maximum likelihood estimators. Dashed lines represent 95% confidence intervals.

Limitations

Noncompliance with protocol biopsy may introduce unmeasurable reporting bias. These very encouraging observations may not be generalizable to patient populations at other medical centers and less experienced surgeons. Additionally, there are limitations inherent in the statistical analyses, particularly as they pertain to our multiparametric MRI test characteristics and the structure of our survival models/analyses.

Interpretation for Patient Care

The very low in-field cancer detection rate at 3 years indicates successful ablation of localized cancers. Conversely, our observed out-of-field detection rate highlights the need for continued surveillance following primary partial gland cryoablation. The overwhelming majority of clinically significant recurrences were low volume and managed with active surveillance or salvage partial gland cryoablation.