Cryoablation of Primary Breast Cancer in Patients Ineligible for Clinical Trials: A Multiinstitutional Study

BACKGROUND. Breast cancer cryoablation clinical trials have strict inclusion criteria that exclude patients with potentially treatable disease. OBJECTIVE. The purpose of this study was to evaluate the safety and outcomes of breast cancer cryoablation without surgical excision in patients ineligible for prospective cryoablation clinical trials due to unfavorable patient or tumor characteristics. METHODS. This retrospective study included women who underwent cryoablation of biopsy-proven unifocal primary breast cancer with locally curative intent, without surgical excision, despite being ineligible for (and thus excluded from) cryoablation clinical trials, across seven institutions between January 1, 2000, and August 26, 2021. Adverse events (AEs) were recorded. Cryoablation procedures were classified as technically successful if they were not prematurely terminated and achieved intended treatment parameters and if the first follow-up imaging examination showed no evidence of residual disease. The results of follow-up biopsies were recorded. Ipsilateral breast tumor recurrences (IBTRs) diagnosed during follow-up were identified and classified as true recurrence or new primary disease. A competing-risk model was used to estimate the cumulative incidence of IBTR accounting for death before IBTR as a competing risk. RESULTS. The final study sample included 112 patients (median age, 71 years). A total of seven of 112 (6.3%) patients had a minor AE; no moderate or major AEs occurred. A total of 110 of 112 cryoablation procedures (98.2%) were technically successful. During a median follow-up of 2.0 years, 22 of 110 patients (20.0%) underwent biopsy for suspicious imaging findings in the ipsilateral breast, which yielded benign concordant findings in nine of 22 patients (40.9%) and IBTR in 12 of 22 patients (54.5%). Overall, 12 of 110 patients (10.9%) experienced IBTR, including seven with true recurrence and five with new primary disease; three of 12 patients (25.0%) with IBTR had received earlier adjuvant or neoadjuvant therapy. When death was accounted for as a competing risk, the cumulative incidence of IBTR was 5.3%, 12.2%, and 18.2% at 1, 2, and 3 years, respectively. CONCLUSION. In select individuals with unfavorable patient or tumor characteristics, breast cancer cryoablation provides a safe alternative to surgery and has good outcomes. These findings may be particularly relevant in patients who are also poor surgical candidates. CLINICAL IMPACT. Breast cancer cryoablation can be safely applied in a larger patient populations than those defined by clinical trial inclusion criteria.