Assessing Tumor Response to Neoadjuvant Chemotherapy using Ultrasound-guided Near Infrared Light

Abstract

The objective of this study is to assess initial tumor vascularity before the initiation of neoadjuvant chemotherapy, monitor the vascular changes at the end of each treatment cycle, and correlate initial vascularity and early vascular changes with the tumor pathological response. Patients eligible for neoadjuvant chemotherapy were recruited and their tumor vascularity was assessed using a near infrared imager coupled with an US system. 33 patients were imaged prior to treatment, at the end of every treatment cycle and before their definitive surgery. The patients’ final pathologic response was graded based on the Miller-Payne (PM) system as non and partial-responders (grades 1-3) and near-complete and complete responders (grades 4-5). The tumor vascularity was assessed from total hemoglobin (tHb), oxygenated (oxyHb) and deoxygenated hemoglobin concentrations (deoxyHb). The tumor vascularity changes during treatment were assessed from a percentage tHb (%tHb) normalized to the pretreatment level. There were 20 MP grade 1-3 tumors and 15 grade 4-5 tumors. Mean maximum pretreatment tHb, oxyHb, deoxyHb levels were significantly higher in the MP grades 4-5 group than in the grades 1-3 group (P=0.002, P=0.003 and P=0.01, respectively). The individual patients’ vascular changes assessed during treatment based on %tHb were statistically significant at the end of cycle 1 (P=0.009). The significance was much higher at the end of cycles 2 and 3 (P<0.001). Our findings indicate that initial tumor vascularity is a good predictor of final pathologic response. Additionally, the vascular changes during early treatment cycles assessed by %tHb can further predict final pathologic response.