MRI Findings After Cryoablation of Primary Breast Cancer Without Surgical Resection

Rationale and Objectives: To retrospectively evaluate findings on serial magnetic resonance imaging (MRI) after cryoablation for breast cancer lesions without subsequent surgical resection. Materials and Methods: This study was approved by the Institutional Review Board and the requirement to obtain informed consent waived. Ductal carcinoma in situ or invasive carcinoma <= 15 mm, nuclear grade 1 or 2, estrogen receptor positive/human epidermal growth factor 2 negative without lymph node metastasis were treated with cryoablation without subsequent excision. Two observers independently reviewed the first two postcryoablation MRIs for shape (none, focus-to-mass, or nonmass enhancement) and suspicion of residual disease (positive or negative). Fisher's exact or the Mann-Whitney U test was used to assess significance. Interobserver agreement on findings was evaluated by calculating kappa values. Results: Fifty-four patients were enrolled. The first and second postcryoablation MRIs were performed 22-171 days and 82-487 days after cryoablation, respectively. Interobserver agreement ranged from fair to moderate (kappa = 0.356 - 0.434). Observer 1 or 2 identified suspicious areas on the first postcryoablation MRI in seven cases (13.0%). These were significantly associated with focus-to-mass shape (vs non-focus-to-mass: nonmass enhancement or none) and residual disease or recurrence suspected by both observers (p < 0.001). There were no cases of both observers identifying suspicious findings on the second postcryoablation MRI. Conclusion: Suspicious findings can be detected within the treated area at the first postcryoablation MRI. These can resolve during subsequent adjuvant therapies and follow-up.