Quantifying molecular breast imaging uptake variability and changes in patients with breast cancer undergoing...

Best practices for quantifying longitudinal changes in 99m Tc-sestamibi uptake with molecular breast imaging (MBI) have not been established. The objective of this work is to quantify the variability of tumor-to-normal tissue 99m Tc-sestamibi uptake measurements in patient data and the resulting impact on categorizing uptake changes throughout neoadjuvant systemic therapy (NST).

In 60 patients with locoregional breast cancer undergoing NST, tumor-to-normal-tissue ratios of average contour counts ( ) and activity concentrations ( ) were calculated from physician contours on craniocaudal and mediolateral-oblique MBI images acquired at pre-NST, mid-NST, and post-NST with a commercial dual-headed system. Measurement variability was quantified in pre-NST images by using different contours and detector views. This analysis was then used to define patient-specific thresholds above which calculated and values at mid-NST and post-NST imaging had 'changed' from pre-NST values.

Pre-NST values ranged from 1-5 to 1-100 and in general decreased by 10-30% at mid-NST and by 50-70% at post-NST. uncertainty was significantly higher than uncertainty (53% vs. 35% median value; paired t -test; P  < 0.007), driven primarily by normal-tissue contour placement within the heterogeneous signal in normal breast parenchyma. In paired comparisons, a significantly higher number of cases 'changed' when the metric was derived from a single image instead of averaged across images (McNemar's test, P  < 0.0125).

By ensuring consistent acquisition conditions and standardizing contour definitions, robust metrics of tumor and normal-tissue uptake can be extracted from heterogenous clinical MBI data for longitudinal quantitative evaluations.