Evaluation of tumor angiogenesis measured with microvessel density (MVD) as a prognostic indicator in nasopharyngeal carcinoma: Results of RTOG 9505

The objective of this study was to evaluate tumor angiogenesis as measured by microvessel density (MVD) as an independent prognostic factor in patients with nasopharyngeal carcinoma (NPC) treated with radiotherapy alone. Eligible patients included those with NPC treated with radiotherapy. Paraffin blocks of the primary tumor had a hematoxylin and eosin–stained section prepared at the block face. One representative section for tumor was stained for factor VIII–related antigen using a standard immunoperoxidase staining technique. MVD was determined by light microscopy in areas of invasive tumor containing the highest numbers of capillaries and microvessels per area. Individual microvessel counts were made on a 200× field within the area of most intense tumor neovascularization. Results were expressed as the highest number of microvessels identified within any single 200× field. Using a breakpoint of MVD