Laser therapy for breast cancer: MR imaging and histopathologic correlation

PURPOSE: To investigate magnetic resonance (MR) imaging guidance of interstitial laser photocoagulation to treat primary breast cancer. MATERIALS AND METHODS: Twenty female patients with symptomatic breast cancers diagnosed at cytologic examination underwent interstitial laser photocoagulation by means of a single fiber prior to surgical excision. Gadolinium-enhanced T1-weighted three-dimensional fast low-angle shot (FLASH) MR imaging was performed before and after laser therapy (median, 48 hours; range, 24-96 hours). Following resection, tumors were mapped in detail histopathologically. The extent of disease, size of laser burn, and extent of residual tumor were correlated with MR findings. RESULTS: Twenty-seven tumors were detected at histopathologic examination in the 20 patients. Five patients had more than one invasive mass. Twenty-five of the 27 tumors were identified as discrete enhancing masses at MR. The two missed invasive foci were obscured on MR images by diffuse patchy enhancement that correlated with the presence of an associated extensive intraductal component. Early (4-hour) follow-up images failed to depict the laser effect. Later (24-96 hours) follow-up images depicted the laser-induced necrosis as a zone of nonenhancement within the residual enhancing tumor. The correlation coefficients (MR vs histopathologic analysis) for the laser-burn diameter and residual tumor were 0.80 and 0.86, respectively. CONCLUSION: Delayed gadolinium-enhanced MR images can help define the extent of laser-induced necrosis and residual tumor after interstitial laser photocoagulation therapy in breast cancer.