Preoperative MRI Among Older Women with Breast Cancer May Lead to Overdiagnosis of CBC

A recent study by Yale researchers, published in the Journal of Clinical Oncology, found that preoperative magnetic resonance imaging (MRI) in women with breast cancer may lead to overdiagnosis of contralateral breast cancers (CBCs) (published online ahead of print; doi: 10.1200/JCO.2015.62.9741). 

Previous research has shown that preoperative MRI detects occult CBCs in women with breast cancer, but the impact of detection on long-term CBC events remains unclear. Thus, Yale researchers examined whether MRI use decreases the occurrence of CBCs and the detection of stages II to IV disease among women who develop a CBC.

Analyzing the SEER-Medicare database, first author Shi-Yi Wang, Md, PhD, (Yale School of Public Health, New Haven, CT) and colleagues assessed overall, synchronous (< 6 months after primary cancer diagnosis), and subsequent (ie, metachronous) stage-specific CBC occurrences in women who were diagnosed with stages I and II breast cancer during 2004-2009 and who were observed through 2011.

They found that, among 38,971 women with breast cancer, 6,377 (16.4%) received preoperative MRI. After propensity score matching, and compared with women who did not undergo MRI, preoperative MRI use was significantly associated with a higher synchronous CBC detection rate (126.4 v 42.9 per 1,000 person-years, respectively; hazard ratio, 2.85; P < .001) but a lower subsequent CBC detection rate (3.3 v 4.5 per 1,000 person-years, respectively; hazard ratio, 0.68; P = .002). However, the 5-year cumulative incidence of CBC remained significantly higher among women undergoing MRI compared with those not undergoing MRI (7.2% v 4.0%, respectively; P < .001). 

The analyses of projected CBC events for 10,000 patients who receive MRI indicated that, after a 5-year follow-up, MRI use would detect an additional 192 in situ CBCs (95% CI, 125 to 279) and 120 stage I CBCs (95% CI, 62 to 193) but would not have a significant impact on stages II to IV CBC occurrences (~ 6; 95% CI, −21 to 47).

They concluded that an increased synchronous CBC detection rate, attributable to MRI, was not offset by a decrease of subsequent CBC occurrence among older women with early-stage breast cancer, suggesting that preoperative MRI in women with breast cancer may lead to overdiagnosis. —Amanda Del Signore