Association Between the Volume Transfer Constant (Ktrans) From Dynamic Contrast‐Enhanced Perfusion MR and HER2 Status in Breast Cancer Brain Metastases

Background With the development of new human epidermal growth factor 2 (HER2)‐targeting therapies, a non‐invasive method of determining the HER2 status of breast cancer brain metastases can be of great clinical value, particularly given the risks of brain biopsy and the possibility of discordance between HER2 status of the primary breast cancer and the brain metastasis. Aims The purpose of this study was to assess whether the volume transfer constant (Ktrans) from dynamic contrast‐enhanced (DCE) perfusion brain MR could assist in identifying the HER2 status of breast cancer brain metastases. Methods With IRB approval for this retrospective study, we searched the electronic medical record at the City of Hope Comprehensive Cancer Center to identify all histopathologically proven breast cancer brain metastases with both preoperative DCE perfusion brain MR and HER2 assessment of the resected/biopsied brain specimens at the City of Hope Comprehensive Cancer Center from 2011‐2022. Mann‐Whitney tests were used to compare the Ktrans of the breast cancer brain metastases. Results There were 9 women in our study cohort with a mean age of 55 years. Our cohort was comprised of a total of 9 breast cancer brain metastases, 3 of which were HER2‐positive, 6 of which were HER2‐negative. The Ktrans of HER2‐positive breast cancer brain metastases was significantly greater than the Ktrans of HER2‐negative breast cancer brain metastases (0.09 min −1 vs 0.02 min −1 , U = 18.00, p = 0.024). Conclusion Ktrans may help to differentiate HER2‐positive from HER2‐negative breast cancer brain metastases, if validated in a large prospective, multi‐center trial.