Phase II study on radiofrequency ablation in stage 0 and I breast cancer without extensive intraductal components.

Abstract

e12094 Background: We reported about a multi-center registration study on radiofrequency ablation (RFA) in early breast cancer (BC) (ASCO2012 #1119). Although various devices and ablation procedure were used, 5-year’s recurrence-free survival was 96% in 425 cases of T1BC treated with RFA alone. To validate complete pathological ablation in BC, we started a non-randomized phase II study in 2013 (UMIN000013836). Methods: Unilateral BC patients with stage 0 (TisN0M0) or I (T1N0M0 or T1N1miM0) were eligible. Tumor diameter of 2cm or less should be diagnosed by ultrasound and MR mammography. RFA was performed by Cool-tip RF ablation system (Covidien, USA). One month later, ablated tissue was collected by core needle biopsy or vacuum-assisted breast biopsy. Cell viability was determined by central review of independent pathologists using tumor specimens stained with hematoxylin–eosin and nicotinamide adenine dinucleotide (NADH) diaphorase. In case of complete ablation, breast irradiation and adjuvant therapy was planned. In case of incomplete ablation, partial mastectomy was recommended. The primary endpoint is complete ablation rate. The secondary endpoints are breast deformity after RFA, relapse-free survival and overall survival for 10 years. Two-step design consisting of 9 cases at 1st step and 20 cases at 2nd step was used for statistical evaluation. We expected complete ablation rate of 95% and 29 cases were needed to reject the null hypothesis that complete ablation rate would be less than 80% at lower threshold. Thus, 32 cases were required. Results: Thirty-six patients were enrolled between February 2013 and May 2016. The mean tumor size was 1.3 cm measured by MR mammography. Two patients were ineligible because of macrometastasis in a sentinel node. Of 34 eligible patients, one patient had viable cancer cells with NADH diaphorase staining in ablated specimens. Finally, complete ablation rate was 97%. As of January 2017, one patient, who refused adjuvant therapy and breast irradiation, had in-breast tumor recurrence adjacent to previously ablated lesion. Conclusions: Long-term follow-up should be needed, but RFA in early BC is a promising strategy instead of breast-conserving surgery. Clinical trial information: UMIN000013836.