Photodynamic Therapy of Malignant Brain Tumors: Preliminary Experiences with Four Patients

Abstract

The ability of hematoporphyrin (Hp) and some chemical derivatives (HpD) to be accumulated in greater amounts and retained for longer periods of time by neoplastic than by normal tissues is the basis of a new phototherapeutic possibility for tumors (Dougherty 1984) called photodynamic therapy (PDT). The technique has been successfully applied to both superficial (Dahlman et al. 1983) and deep-seated tumors (Dougherty et al. 1981); in the latter case, the light emitted from the laser source is focused into an optical fiber, which is then inserted into the tumor mass. The photoactivation of tumor-localized Hp or HpD is most frequently obtained by irradiation with red light (600–630 nm; Dougherty 1984): these wavelengths have the dual property of not being absorbed by common cell constituents and of having a significant penetrating power into biological tissues. As a consequence, the Hp-promoted photodamage is restricted to the level of the neoplastic areas, which are illuminated in a uniform way for diameters of up to 1cm (Dougherty et al. 1981).