Photodynamic therapy in the treatment of brain tumours. A feasibility study.

Background: Photodynamic therapy (PDT) constitutes a treatment modality that combines a photosensitizing agent with exposure to laser light in order to elicit phototoxic reactions that selectively destroy tumor cells and spare normal cells. PDT is a local treatment modality without long-term systemic effects. Its application can be repeated more than once to the same area without accumulative effects.

Methods: Patients diagnosed with primary brain tumors were treated with PDT. Treatment consisted in administration of the photosensitizer followed by craniotomy, surgical resection and laser illumination of the surgical bed. Primary brain tumors received also temozolomide-based chemotherapy and radiotherapy (RT).

Results: From May 2000 to December 2010, 41 patients (27 male, 14 female) with a median age of 49 years (range 13-70) diagnosed of primary brain tumors were included in the study. In 7 patients PDT was repeated at the time of the relapse. In 22 episodes PDT was part of the initial treatment of primary brain tumors and in 26 episodes was part of the treatment at relapse. Median PFS observed was 10 months for GBM (95% confidence interval 5.7-14.3), 26 months for AA (95% CI 4.5-47.5), and 43 months for OD (95% CI 4.5-47.5). Median OS was 9 months for GBM (95% CI 2.3-15.7), 20 months for AA (95% CI 0.0-59) and 50 months for OD (95% CI 32.5-67.5). The apparent discrepancy between PFS and OS data is due to patients not censored for PFS because they die from causes other than tumor progression. Median OS since first diagnosis was 17 months for GBM (95% CI 15.2-17.8), 66 months for AA (95% CI 2.9-129.1) and 122 months for OD (95% CI 116.1-127.8). Side effects were mild and manageable.

Conclusions: This study confirms that PDT can be considered as an adjunctive to surgery and/or RT and chemotherapy in the treatment of brain tumors, excluding those patients with thalamic or brain stem locations. It adds therapeutic effect without adding significant toxicity. In order to improve its contribution, it is essential to find new drugs with more penetration in order to destroy tumor cells more deeply at resection margins.