Seven dogs with thyroid gland carcinoma were treated with 131I and hormone suppressive therapy either alone (3 dogs) or in combination with surgery (3 dogs) or 137Cs teletherapy and chemotherapy (1 dog). Empirically chosen doses of 75 to 137 mCi of 131I were given orally (2 dogs) and intravenously (5 dogs). Adverse effects were limited to acute, transient bone marrow hypoplasia and pancytopenia. Nominal objective reduction in tumor volume or size and number of pulmonary metastases was observed in 4 dogs treated with 131I and thyroxine. Of these 4 dogs, 2 had stable disease for periods of 4 and 12 months while a third dog had stable disease for 27 months following two 131I treatments at 3 month intervals. The fourth dog had progressive disease. Two dogs with mediastinal metastases showed reduction in localization of 99mTc pertechnetate and radioiodine following 2 and 3 treatments using 131I. It appears that relatively high doses of 131I can be used safely for the treatment of canine thyroid tumors and that further investigation can be justified to define its efficacy.
A study was conducted in the normal canine esophagus to compare continuous wave (CW) and pulsed laser light for photodynamic therapy with Photofrin (4 mg/kg). Forty-eight hours post-injection, 630 nm laser light (CW light from an argon-pumped dye-laser and pulsed light from a KTP/532-pumped dye-laser) was delivered using a 24 mm diameter cylindrical esophageal PDT balloon positioned at either distal or proximal esophagus. A 1.0 cm cylindrical diffuser placed in the center of the balloon delivered 300 J/cm of light at an intensity of 400 mW/cm. Three dogs received CW light proximally and pulsed light distally. Four dogs received CW light distally and pulsed light proximally. The light dose delivered to the esophageal mucosa was measured using three isotropic probes placed on the balloon wall. Laser-induced fluorescence technique was used to compare photosensitizer fluorescence intensities at distal and proximal locations. Similar mucosal light doses and drug fluorescence intensities were verified for sites receiving pulsed or CW laser light. Two days after light delivery, the dogs were endoscoped to evaluate the severity of the lesions. While some response variability was observed among different animals, endoscopic examination of the lesions revealed comparable injury from CW and pulsed light in each subject. The animals were then euthanized and necropsies were performed. Based on the gross and histological examination of the lesions, the CW and pulsed laser-induced injuries could not be distinguished.
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