DePeri, Elizabeth R.

604 Background: Many patients with localized breast cancer undergo breast conservation therapy. Partial breast irradiation (PBI) is a technique that reduces irradiated tissue volume and decreases treatment time. Appropriate patient selection for this technique is critical. We studied the influence of pre-operative breast MRI on patient selection for PBI. Methods: Between 05/04 and 05/05, 231 women with newly diagnosed breast cancer underwent pre-operative bilateral breast MRI (median age = 64, range 34 to 89). Following initial clinico-pathologic review, patients were deemed to be eligible for PBI based on the NSABP B39 protocol if they satisfied its inclusion criteria (tumor size ≤3 cm, ≤3 positive nodes, negative surgical margins, lack of multicentric disease), derived through physical examination, mammography and/or ultrasonography. Breast MRI scans of all patients deemed eligible for PBI by these criteria were then reviewed to determine the impact of the MRI findings on their eligibility for PBI. Only patients who had pathological assessment to correlate with the MRI findings were included in the analysis. Results: Based on the NSABP B39 inclusion criteria, 186 patients (81%) were considered to be appropriate candidates for PBI without influence from MRI findings. Of these 186 women, MRI findings led to pathologically proven additional disease that altered the recommendations for PBI in 26 patients (14%). Mammographically occult, biopsy proven multicentic disease was detected in the ipsilateral breast in 13 patients (7%), whereas 5 women (2.7%) had mammographically occult, biopsy proven multicentric disease in the contralateral breast. In 8 patients (4.3%), pathological assessment confirmed more extensive local disease than was detected by breast MRI. Conclusions: Up to 14% of patients initially deemed eligible for PBI were later found to be ineligible because of breast MRI findings. Ipsilateral multicentric disease was identified in 7%, contralateral disease was discovered in 2.7%, and more extensive local disease was noted in 4.3%. Bilateral breast MRI complements other imaging modalities in determining eligibility for PBI by identifying mammographically occult disease in patients for whom PBI may be inappropriate. No significant financial relationships to disclose.

614 Background: An analysis of preoperative bilateral breast MRI at our institution suggests that approximately 1/3 of patients with newly diagnosed breast cancer may have a mammographically occult, but MRI-evident, contralateral breast abnormality. A number of these patients will have pathologic confirmation of carcinoma in the contralateral breast. Identification of risk factors to predict which patients are at high risk for having a mammographically occult contralateral carcinoma was performed. Methods: MRI results of 401 women with newly diagnosed breast carcinoma who underwent MRI were reviewed (overall group; OG). Patients with a contralateral abnormality identified only by MRI were analyzed to determine the incidence of contralateral carcinoma. In addition, the following risk factors were evaluated: Age at diagnosis, menopausal status, tumor size, nodal status, ipsilateral tumor histology, tumor grade, hormone receptor status, Her-2/neu receptor status, and whether the patient had a palpable vs. mammographically detected abnormality. Results: Pathologically confirmed contralateral carcinoma (CC) was found in 13 patients (3.2%). Similar percentages of patients in both groups (OG and CC) were noted in regard to tumor size, histology, grade, nodal status, Her-2/neu receptor status, and method of detection (palpable vs. mammographic). However, median patient age was 71 (CC) vs. 62(OG); 92% (12/13) were postmenopausal (CC) compared to 75% (OG); and 100% were ER positive (CC) vs. 81% percent (OG). Conclusions: Older, postmenopausal women who have ER + tumors may have a higher likelihood of having synchronous, contralateral, mammographically occult, MRI-detected breast carcinoma. Preoperative MRI may be beneficial in patients with similar risk factors; however, further follow up and additional experience is needed for confirmation of these findings. No significant financial relationships to disclose.

603 Background: Breast MRI may be useful for detecting mammographically occult ipsilateral carcinoma in newly diagnosed breast cancer. Our initial experience with breast MRI, demonstrated 16% of patients to have additional breast disease detected only by preoperative MRI. We further analyzed our findings to identify an association between patient factors and MRI detected disease. Methods: Preoperative MRI scans of 390 women with newly diagnosed breast cancer were reviewed. Using only patients with pathologic verification, the incidence of mammographically occult ipsilateral cancer was determined. Patient and tumor characteristics were further analyzed to identify factors which may predict pathologically positive MRI findings. Results: Of the 390 women undergoing preoperative MRI, 120 (31%) had ipsilateral findings requiring biopsy. Pathologically verified additional ipsilateral cancer was detected in 62 (16%). Multicentric disease was detected in 32 (52%) and multifocal or more extensive local disease in 30 (48%). The median age of all patients was 62 (27% premenopausal) whereas the median age of those with MRI detected additional carcinoma was 55 (44% premenopausal). Of those with additional disease detected by MRI, 74% had index lesions =1 cm and 63% node negative. The most common histology of the index lesion was infiltrating ductal carcinoma in 64%. In the 62 patients found to have additional disease by MRI the most common histology included infiltrating ductal carcinoma (58%), ductal carcinoma-in-situ (34%) and infiltrating lobular (8%). The histology of the MRI detected additional disease was identical to the index lesion in 71%. Conclusions: In women with newly diagnosed breast cancer, there was a 16% incidence of pathologically proven, mammographically occult ipsilateral disease detected by MRI. Patients found to have additional disease tended to be younger, premenopausal or have index tumors =1cm. The contribution of preoperative MRI in breast cancer management continues to evolve. A lower threshold for obtaining breast MRI may be appropriate in selected subsets of breast cancer patients. No significant financial relationships to disclose.