Background and Objective: One of the major side effects of photodynamic therapy (PDT) employing Photofrin as the sensitizer is enhanced photosensitivity of the skin. The basic mechanism in PDT damage is believed to be the formation of singlet oxygen and radical species. N-acetylcysteine (NAC) increases glutathione levels and is known to prevent pathology elicited by radicals and reactive species. Study DesignlMaterials and Methods: NAC was tested in a randomized, open label study for its protective effect on skin photosensitivity. Twenty-seven patients treated with PDT for central obstructive lung cancer or esophageal cancer received either "early" or "delayed" NAC, starting 5 or 10 days after Photofrin, in a dose of 3 x 600 mg per day for 5 da s. Light, obtained from a halogen lamp (fluence rate 200 mW-cm-') was used to illuminate skin patches of 2.5 cm2 on the back (10, 25, and 50 Jscm-'). Skin response was measured by using a visual scoring system and by measuring the redness using a reflectance meter. Results: Skin responses varied from no changes at 10 J-crn-' to redness with edema at energies of 50 J-cm-'. In the absence of edema, measurements with the reflectance meter appeared to be more sensitive than visual scoring.
Conclusion:
In a limited number of patients, there was a trend for decreased sensitivity after NAC, but statistical analysis failed to show any significant protective effect of this short course of NAC.