Von Willebrand factor levels do not predict or diagnose radiation pneumonitis

In search for an index of endothelial injury that would provide an early diagnosis of radiation pneumonitis, we investigated the plasma levels of von Willebrand Factor (Factor VIII Related Antigen, FVIII:RAg) in 14 patients undergoing pulmonary irradiation. This study was based on observations indicating that damage to the endothelium-rich pulmonary parenchyma may produce alterations in the synthesis, storage or release of FVIII:RAg, detectable in plasma. There was no correlation between FVIII:RAg levels and radiation pneumonitis, radiation dose, volume of irradiated lung, tumor burden, or time-interval between exposure and sampling. The heterogeneity of the neoplasms and the inconstant effects of radiation in the tumor vasculature are among several variables that may explain this lack of correlation. The plasma levels of FVIII:RAg cannot be used to diagnose or predict radiation pneumonitis.