How to measure breast cancer tumoral size at MR imaging?

ObjectiveTo compare the accuracy of different MR sequences to measure tumor size.MethodsEighty-six women (mean age: 53 years (30-78)) who underwent preoperative MRI for breast cancer were included. Maximal diameters of the index tumor (IT) and of the whole extent of the tumor (WET) were measured on T2-weighted (T2W) sequences, on dynamic contrast-enhanced (DCE) T1-weighted (T1W) sequences and on Maximal Intensity Projection (MIP) reconstructions. Agreements with pathological size were evaluated using concordance correlation coefficient (k).ResultsMedian pathological size of IT was 20 mm (13-25 mm, interquartile range). Median pathological size of the WET was 29 mm (16-50 mm, interquartile range). Measurement of IT showed a good concordance with pathological size, with best results using T2W (k = 0.690) compared to MIP (k = 0.667), early-subtracted DCE frame (k = 0.630) and early-native DCE frame (k = 0.588). IT was visible on T2W in 83.7% and accurately measured within 5 mm in 69.9%. Measurement of WET was superior using early-subtracted DCE frame (k = 0.642) compared to late-native frame (k = 0.635), early-native frame (k = 0.631), late-subtracted frame (k = 0.620) and MIP (k = 0.565). However, even using early-subtracted frame, WET was accurately measured within 5 mm only 39.3%.ConclusionIf visible, IT size is best measured on T2W with a good accuracy (69%) whereas WET is best estimated on early-subtracted DCE frame. However, when adjacent additional sites exist around IT, suspected surrounding disease components need to be proved by pathological analysis.