SAN DIEGO – Magnetic resonance imaging identified additional breast cancer in 11% of women with newly diagnosed disease who were otherwise eligible for partial breast irradiation, preliminary results from an ongoing study demonstrated.
Treatment of these patients with limited radiation fields would result in undertreatment of the tumor and could potentially compromise disease control, Dr. Paige L. Dorn said at the meeting.
Treatment for early-stage breast cancer with partial breast irradiation is currently under investigation in a multi-institutional, randomized controlled trial, NSABP B-39. Retrospective data from the University of Chicago Hospitals and Clinics and other institutions “have shown that MRI is able to find additional disease in 5%–10% of otherwise partial breast irradiation–eligible candidates, based on mammogram and ultrasound alone,” said Dr. Dorn of the university's department of radiation oncology. “The purpose of this study is to evaluate the utility of MRI in detecting clinically occult foci of disease in a prospectively identified cohort of partial breast irradiation candidates uniformly undergoing MRI in addition to mammogram and ultrasound.”
Since June of 2009, all imaging and surgical pathology have been reviewed in a multidisciplinary setting by radiologists, surgeons, pathologists, and radiation oncologists at the university to determine candidacy for partial breast irradiation. In patients eligible for partial breast irradiation, Dr. Dorn and her associates prospectively documented whether MRI identified additional lesions in the same quadrant (multifocal), a different quadrant (multicentric), or the contralateral breast. They biopsied suspicious MRI findings to confirm pathology and then prospectively recorded whether MRI findings prompted a change in the eligibility for partial breast irradiation according to the entry criteria outlined in NSABP B-39. Prospectively collected data was verified by retrospective evaluation of all patient records.
Of 486 patients screened by the researchers between June 2009 and October 2010, Dr. Dorn reported that 91 (18.7%) were deemed eligible for partial breast irradiation based on mammogram, ultrasound, and pathology alone. Their median age was 56 years.
Of the 91 patients, 66 had invasive ductal or lobular carcinoma, 18 patients had ductal carcinoma in situ, and 7 had invasive lobular disease. MRI identified additional disease in 10 patients. Multifocal disease was seen in 9 of these patients, while contralateral disease was confirmed in 1.
The researchers also found that MRI was more likely to identify occult disease in patients younger than age 50, in those who were premenopausal, and in those who had tumor sizes of 2 cm or greater.
Dr. Dorn said the study had certain limitations, including the fact that the potential impact of MRI on disease outcomes after partial breast irradiation remains unknown. “Whether these multifocal lesions would have been surgically excised is unknown,” she added.
Based on the results of this and other studies, she concluded that MRI “should be increasingly considered as part of the work-up for partial breast irradiation candidates. MRI may help refine criteria for patient selection, especially in those with higher-risk features. We plan to continue this prospective study to further define the role of MRI in this population.”
MRI 'should be increasingly considered as part of the work-up for partial breast irradiation candidates.'
Source DR. DORN