Increased uptake of Tc-99m-HL91 in tumor cells exposed to X-ray radiation

Tc-99m-HL91, a hypoxic marker, may be a predictor of tumor response to radi otherapy and an indicator of tumor oxygenation in the course of treatment. In this study, serial changes in Tc-99m-HL91 uptake were observed in the no rmoxic condition in a human bladder cancer cell line exposed to a single do se or a fractionated dose of 10 Gy with an x-ray beam. The uptake per cell increased during cell growth retardation induced by the irradiation. This f inding indicates that Tc-99m-HL91 uptake is affected by injury to cells due to radiation; it may therefore be difficult to correctly assess the tissue oxygenation status during radiotherapy with Tc-99m-HL91.