Correction by the skin-to-chest wall distance in near-infrared spectroscopy and assessment of breast cancer responses to neoadjuvant chemotherapy

Abstract

The measurement of hemoglobin (Hb) concentrations in breast cancer by near-infrared spectroscopy is useful for the assessment of responses to neoadjuvant chemotherapy (NAC). However, the chest wall muscles may affect this measurement. We corrected Hb concentrations based on the skin-to-chest wall distance. Corrected Hb was compared with uncorrected Hb as a marker of treatment responses in breast cancer patients. We measured total Hb (tHb) in breast cancer using a near-infrared time-resolved spectroscopy system in 10 patients before chemotherapy and after the first and second courses of NAC. To assess the skin-to-chest wall distance and thickness of tumors, ultrasound images were obtained using an ultrasonography probe with the spectroscopic probe. Net tHb (tHbnet) was calculated by subtracting tHb in normal breast tissue from cancer tHb. Patients underwent positron emission tomography with [18F] fluorodeoxyglucose (FDG) before chemotherapy and after the second course of NAC. FDG uptake was evaluated using the maximum standardized uptake value (SUVmax). tHb, tHbnet, and SUVmax in cancer significantly decreased in the course of chemotherapy. The change in tHbnet was larger than that in tHb. Although a correlation was not observed between the change in tHb and that in SUVmax, a positive correlation was noted between the change in tHbnet and that in SUVmax. Corrections by the skin-to-chest wall distance in spectroscopy led to the change in Hb concentrations being more similar to that in FDG uptake after NAC in breast cancer. tHbnet has potential as a reliable biomarker of breast cancer.