Adjuvant intraoperative photodynamic therapy in experimental colorectal cancer using a new photosensitizer.

BACKGROUND: Photodynamic therapy is a promising anticancer modality. The effect of adjuvant intraoperative photodynamic therapy (AIOPDT) using photosensitizers Photofrin or mesotetra (hydroxyphenyl) chlorin (m-THPC) was evaluated in a mouse model of local recurrence of colorectal cancer. METHODS: Animals were injected with either photosensitizer 24 h before surgery. Standard excision included removal of all visible tumour by a surgeon blinded to both the drug and subsequent light treatment. Following surgery the tumour beds were illuminated with either 70 J cm-2 of 510-nm light (Photofrin) or 2.5 J cm-2 of 652-nm light (m-THPC). Control groups had either surgery only, surgery and Photofrin only, surgery and m-THPC only, or surgery and either 652-nm or 510-nm light. RESULTS: After a 70-day observation period, the local recurrence rates were 25-26 per cent in the photodynamic therapy groups compared with 80-90 per cent in the control groups (P < 0.001). CONCLUSION: AIOPDT using either Photofrin or m-THPC was equally effective in reducing local recurrence in this model. Since treatment time with m-THPC was only 25 s compared with 11 min with Photofrin, the use of the former new photosensitizer increases the practicality of AIOPDT and could enable the laser to be replaced with cheaper, less intense light sources.

Treatment of head and neck cancer with photodynamic therapy: results after one year.

Photodynamic therapy (PDT) is a new and promising treatment modality for the treatment of malignant disease. This paper reports the preliminary experience of our group in the use of this therapy for the treatment of tumours arising in the head and neck. The majority of treatments in these cases have used a second generation systemic photosensitizer, meta-tetrahydroxyphenylchlorin (m-THPC). Two other cases were treated with either Photofrin 2 (a first generation systemic sensitizer) or with the topical photosensitizer, delta-aminolaevulinic acid (delta-ALA). The initial results have been encouraging with good clinical responses evident in patients presenting with a variety of differing tumour types. We feel there is now sufficient evident of the efficacy of this treatment to warrant a multicentre prospective study into the treatment of early head and neck cancer with PDT.