Quantitative Estimates of Vascularity in Solid Tumors by Non-Invasive Near-Infrared Spectroscopy

We examined the relationship between non-invasive estimates of the tumor hemoglobin concentration by near-infrared spectroscopy (NIBS) and histological scores of tumor vascularity by Chalkley counts in seven tumor lines in nude mice [malignant gliomas: U87, U118, U373; small cell lung cancers (SCLC): 54A, 5413, DMS79; prostate cancer: MatLyLu (MILL) ]. We also evaluated the effect of continuous anti-angiogenic treatment with TNP-470 on tumor hemoglobin concentration and tumor vascularity in U87 and MILL tumors. Non-invasive LAIRS recordings were performed with a custom-built flash near-infrared spectrometer using light guidecoupled reflectance measurements at 800±10 nm. Chalkley counts were obtained from CD31-immunostained cryosections. The LAIRS recordings in arbitrary absorbance units increased with tumor size in the individual tumors until a plateau was reached at approximately 150 mm3. This plateau was relatively tumor line-specific. LAIRS recordings at the plateau phase were strongly correlated (P