Photodynamic therapy of malignant primary brain tumours: clinical effects, post-operative ICP, and light penetration of the brain.

Abstract

Abstract We are reporting our experience with intraoperative PDT in 32 patients with malignant supratentorial gliomas; in 19 cases the tumour was recurrent. There were 20 males and 12 females with an age range of 17‐73 (mean = 45) yr. The first 8 patients in this series received HpD (Photofrin I) and the next 24 received DHE (Photofrin II). A photo‐illuminating device, of the author's design, was coupled to an argon dye pump laser in order to deliver light at 630 nm to a tumour cavity created by radical tumour resection and/or tumour cyst drainage. The total light energy delivered ranged from 440 to 3888 J and the light energy density ranged from 8 to 68 J cm−2.There were two post‐operative deaths as the consequence of hematoma accumulation in an extensive tumour resection cavity. In two patients neurological function was worse post‐operatively and did not recover. Post‐operative cerebral edema was pronounced in eight cases and required emergency craniotomy in two patients (the histology from both showed hemorrhagic necrosis of residual tumour). We have fashioned continuous post‐operative ICP measurements in the last 15 patients treated with PDT and compared the values to those obtained from cases with malignant gliomas who did not have PDT; the mean ICP was significantly greater in the PDT group. Four patients developed wound infections; two of these required surgical treatment. Four patients, two of whom were hemiparetic, developed deep vein thrombosis and required anticoagulant therapy. There were no adverse systemic reactions to the administration of either photosensitizer and only 3 skin photosensitivity reactions.Follow up has ranged from 1 to 26 months at the time of writing; 38% were still alive; in the interval between PDT and death, the deaths per observation year was 1.11 for the whole group and 1.00 when the two post‐operative deaths are excluded. In the interval between first diagnosis and death the rate was 0.45 deaths per observation year. Photodynamic therapy of malignant brain tumours using surface or cavitary photo‐illumination can be carried out with acceptable risk.In eight patients we determined the penetration depth of light in brain tissue in vivo by reading the detected light flux from a fiber passed radially into the brain towards the centre of the irradiation volume. The optical fiber consisted of a single 400 μ.m, cleaved fiber fixed in a 17‐gauge biopsy needle coupled to a photometer. The light penetration depth ranged from 0.8 to 4.9. The mean PD values in the‘tumour’group and the‘brain’group was 2.9 ± 1.5 and 1.5 ± 0.43, respectively. We attribute this significant difference to the differences in the absorption and scattering properties of brain and tumour.