Abstract No. 2 ▪ ABSTRACT OF THE YEAR Breast Cancer Recurrence After Cryoablation

Cryoablation is a minimally invasive technique that has been shown to be effective in select patients with breast cancer. Most outcome data have centered around treatment of small breast cancers. We present our technique and in-breast recurrence rate with 60 patients with breast cancer who were poor surgical candidates or refused surgery and underwent cryoablation of primary breast cancer treated from January 2017 to March 2023. Dataline (Memorial Sloan Kettering Database) queried retrospective data of patients with primary breast cancer treated with cryoablation. Electronic medical records and PACS were reviewed for patient data. The procedural technique was as follows: Patients with tumor size range larger than 1.4 cm were treated with multiple probes (1 probe placement or repositioned for each cm of disease). Freeze thaw cycle ranged from 5-10 minutes freeze, 5-8 minutes passive thaw, and 5-10 minutes freeze at 100% intensity, followed by active thaw to remove probes. Procedures were performed with minimal or no sedation depending on the eligibility and preference of the patient. Follow-up imaging was performed 3 months after the procedure with mammogram and ultrasound and possibly contrast-enhanced mammogram or MRI based on patient eligibility and preference. Out of the 60 treated patients, 48 had invasive ductal carcinoma (IDC), 5 patients had invasive lobular carcinoma, and 7 patients had other histology. Tumor size ranged from (0.3-9 cm), with an average size of 2.5 cm ± 1.8 cm. In a median follow up of 16 months, there was a recurrence rate of 10% (6 patients). Patients with poorly differentiated disease had higher risk of recurrence (RR 5.5 95% CI 1.12-27.19, p = 0.0365), while ILC status, ER/PR status and TNBC status did not contribute to the risk. Tumor size did not differ between recurrence and nonrecurrence groups (nonrecurrence group mean 2.54 ± 1.93 cm, recurrence group mean 2.53 ± 0.96 cm, p = 0.985). In a nonsurgical population with average tumor size of 2.5 cm (tumor size range of 0.3-9 cm), recurrence rate is 10% at 16 month median follow-up. Therefore, with the use of treatment techniques as described, cryoablation can be performed effectively in patients with varying tumors.