Significantly increased lesion size by using the near-infrared photosensitizer 5,10,15,20-tetrakis (m-hydroxyphenyl) bacteriochlorin in interstitial photodynamic therapy of normal rat liver tissue

Background and Objective: Penetration of tissues by activating light ultima tely limits the size of the lesions achievable in interstitial photodynamic therapy. Measurements of the wavelength-dependence of tissue optical prope rties suggest that substantial improvements may be possible, particularly i n pigmented organs such as the liver, by using drugs absorbing at near infr ared wavelengths. Study Design/Materials and Methods: In this study, the extent of light indu ced necrosis with the photosensitive agents Photofrin (activated at 632 nm) , meta-tetra(hydroxyphenyl) chlorin (mTHPC) (activated at 652 nm) and 5,10, 15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (mTHPBC) (activated at 740 n m) are compared in normal rat liver. Interstitial irradiation of mTHPBC-sen sitized liver tissue resulted in significantly larger necrotic areas than i rradiation of Photofrin and mTHPC-sensitised livers. Conclusion: The results illustrate the advantage of near-infrared photosens itizer activation and point to a specific role for mTHPBC in the interstiti al treatment of liver tumours. Lasers Surg. Med. 27:235-240, 2000. (C) 2000 Wiley-Liss, Inc.