## 3 PDT in Veterinary Oncology
### Carcinomas
BPD-MA (Verteporfin, 0.5 mg/kg) and diode laser (690 nm) were used to treat four dogs with squamous cell carcinoma, which originated in the nasal planum (two cases), rostral mandible, and nasal cavity. A few days after treatment, necrosis was observed in the tumor site. It was suggested that a protocol with a shorter drug-light interval could be an interesting option to target tumor vasculature [105]. The same author later published the effectiveness of the antivascular PDT based on the same compound (BPD-MA, 0.5 mg/kg) and the use of a 690 nm diode laser. Despite tumor recurrence, the treatment was a promising method for treating dogs' squamous cell carcinoma and adenocarcinoma (oral and nasal) [106]. The l3,17-bis [1-carboxypropionyl] carbamoylylethyl-3-ethehenyl-8 ethoxyiminoethylidene-7-hydroxy-2,7,12,18-tetramethyl porphyrin sodium (PAD-S31) was used in a cat with a basal cell carcinoma. PAD-S31 was administered intravenously and irradiated with an argon laser (670 nm, 150 J/cm\({}^{2}\)). Three sessions of the PDT were performed, and no lesion recurrence was reported [107]. After radiotherapy's tumor recurrence, three dogs affected by intranasal carcinoma were treated with alloronin sodium. In this report, PDT induced almost complete remission and prolonged survival time, suggesting that it is a functional therapeutic approach for recurrent intranasal carcinomas [108]. The use of 5-ethylamino-9-diethylaminobenzo(a)phenothiazinium chloride (EtNBS) was considered safe for dogs and cats. Two feline sublingual squamous cell carcinomas showed minor response; six feline facial squamous cell carcinomas showed partial response in two cases and complete long-term responses in four cases. A cat with eyelid squamous cell carcinoma presented a partial response to therapy. Two dogs with intraoral squamous cell carcinomas showed a case of minor response and another of complete long-term responses [96]. Two dogs and a cat diagnosed with intranasal adenocarcinomas were submitted to a PDT session. Overall, all animals presented facial swelling after PDT with pyropheophoride-a-hexyl ether (HPPPH) without the need for treatment and no photosensitizer-associated adverse effects. PDT decreased the frequency and severity of some clinical signs, such as epistaxis, sneezing, and nasal content release, demonstrating the ability to control the disease for some time [109]. HPPH-based PDT was performed in 51 cats with naturally occurring facial skin squamous cell carcinomas. Outcomes of one-year follow-up pointed to local control of 62% of the neoplasms and hematological and biochemical toxicity or clinical side effects [110]. HPPH-based PDT was investigated in four dogs. Three dogs had squamous cell carcinomas in the rostral mandibula, ventral abdominal skin, and footpad. The other dog had an apocrine gland adenocarcinoma of the skin of the muzzle. After PDT, eschar formation occurred. Two months later, the squamous cell carcinomas were considered complete responses. The dog with apocrine gland adenocarcinoma remained unchanged for 56 weeks after treatment. This study included three cats with squamous cell carcinoma, which showed complete responses for 60 days [111]. Eleven dogs diagnosedwith oral squamous cell carcinomas were treated with HPPH, intravenously injected at a 0.3 mg/kg dose. Tumors were irradiated 48 h later at 665 nm with 100 J/cm\({}^{2}\). Eight dogs were considered cured without recurrence for 17 months. PDT outcome was comparable to surgical removal, but was superior regarding the aesthetic results [112]. Ten cats were diagnosed with carcinomas, with one of the animals presenting squamous cell carcinoma and carcinoma in situ. The patients were treated with chloro-aluminum sulfonated phthalocyanine (CASPc, 1 mg/kg) and irradiation of 50-150 J/cm\({}^{2}\)[113]. Tumors with more than 1.5 cm were surgically thinned before PDT. As the first three animals produced oedema, dexamethasone sodium phosphate was administered by intravenous infusion for approximately 10 min before laser irradiation of most animals.