BACKGROUND AND PURPOSE: To determine if laser Doppler flowmetry could be used to non-invasively evaluate microvasculature function after radiation therapy (RT), we assessed blood flow response to heating in women following RT after breast conservation. MATERIALS AND METHODS: Forty women with unilateral stage I/II breast cancer treated with conservative surgery and RT were evaluated at varying intervals post RT. Ten patients were retested after an interval of 55 to 57 months to assess reproducibility of the control data. A laser Doppler probe fitted into a heat source was used to non-invasively measure blood flow in a small area of skin on the treated breast and a matched area on the untreated side. The heating element increased skin surface temperature to 40 degrees C, permitting assessment of heat stress induced changes in blood flow. RESULTS: Blood flow increased in response to heating in the untreated and treated breast skin, however the magnitude of the increase was significantly greater in the non-irradiated skin. The difference in relative blood flow to the heat stress was found to be greatest in patients < or =6 months post RT. In the patients who were >36 months post RT, there was no significant difference seen in relative blood flow between the irradiated and non-irradiated sides. Cutaneous blood flow response to the heat stress was very reproducible when women were reassessed 55 to 57 months after initial testing. CONCLUSIONS: Laser Doppler flowmetry can quantify the reduced response of irradiated microvasculature to a heat stress. The difference in relative blood flow to a heat stress is greatest in patients < or =6 months post RT, and normalized in patients >36 months post RT.
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