Monica Morrow, MD, the Anne Burnett Windfohr Chair of Clinical Oncology and Chief of the Breast Service, Department of Surgery, at Memorial Sloan-Kettering Cancer Center, New York, congratulated Christiane K. Kuhl, MD, and colleagues for “an innovative approach to making screening magnetic resonance imaging (MRI) more accessible.”

But Dr. Morrow cautioned against using low-grade ductal carcinoma in situ (DCIS) as a surrogate for breast cancers that are “not important.” She said, “We need to keep in mind that every single prospective randomized trial of DCIS radiotherapy, vs no radiotherapy, showed that the risk of progression to invasive cancer was equal, regardless of the grade of DCIS. I’m not sure that this, in and of itself, is a good surrogate.”

Dr. Morrow also suggested that if the two modalities detect different types of cancers, a randomized trial would be necessary to prove MRI superior to mammography, perhaps with an endpoint of breast cancer–specific survival.

Presenter’s Response

Dr. Kuhl agreed on the need for additional data if MRI is going to be used for screening. “But this study shows proof of principle,” she maintained. “Can we think of using MRI for mass screening? I think the answer is ‘yes, maybe.’”

She further explained, “I don’t think MRI will identify different cancers, but I think MRI is specifically ‘blind’ to cancers and DCIS that don’t have the proteomic tools required for growth and metastasis. Absence of enhancement is not necessarily equivalent to low nuclear grade—there are cases of low-grade DCIS that show strong enhancement on MRI, and there are low-grade invasive cancers that do kill women. So we do not claim that we can disregard all low-grade DCIS—but it is possible that we can indeed disregard ­nonenhancing DCIS. You can think of MRI as in vivo proteomic imaging. Enhancement on MRI may be more accurate to classify the prospective biologic behavior of breast lesions than mere structural changes observed on light microscopy. So being blind for nonenhancing DCIS—not low-grade DCIS—may be a virtue rather than a disadvantage.” ■

Disclosure: Dr. Morrow reported no potential conflicts of interest.