Vascular-targeted photodynamic therapy with glucose-conjugated chlorin e6 for dogs with spontaneously occurring tumours

Background: Photodynamic therapy (PDT) using photosensitisers is a minimally invasive treatment for malignant tumours. However, ideal photosensitisers are not yet established. Recently, we developed a new photosensitiser, glucose-conjugated chlorin e6 (G-Ce6).

Objectives: To evaluate the clinical efficacy of vascular-targeted PDT (VTP), a type of PDT utilising a short drug-light interval, using G-Ce6 to treat spontaneously occurring tumours in dogs.

Methods: Five dogs with spontaneously occurring tumours (malignant melanoma: three; haemangiopericytoma: two; and squamous cell carcinoma: one) were subjected to VTP. These dogs were intravenously injected with G-Ce6 at doses of 1-3 mg/kg 5 min before laser irradiation. Tumours were superficially or interstitially irradiated using a 677-nm diode laser.

Results: Repeated VTP decreased tumour size, yielding complete remission in three dogs. Complications such as oedema surrounding normal tissues and fistulae were observed, and the oedema was self-limiting. The fistula was cured by debriding the necrotic tissues formed after VTP.

Conclusions: Our findings demonstrate that VTP using G-Ce6 had antitumour effects in dogs with spontaneously occurring tumours.