Concomitant liposomal doxorubicin and daily palliative radiotherapy in advanced feline soft tissue sarcomas

Local recurrence of feline soft tissue sarcomas is common despite aggressive treatment. Liposomal doxorubicin might serve as a depot radiosensitizer if administered concomitantly with daily radiotherapy and thus improve tumor control. In this pilot study, the feasibility of concomitant liposomal radiochemotherapy was evaluated in a palliative setting in 10 cats with advanced soft tissue sarcomas. Cats were treated with median number of 5 (range 5-7) daily fractions of radiotherapy and a median total dose of 20 Gy (range 20-31.5 Gy). One dose of liposomal doxorubicin was administered at the beginning of radiotherapy. Seven cats received further free or liposomal doxorubicin after completion of the liposomal doxorubicin/radiation protocol. Seven of the treated 10 cats (70%) achieved a partial (n=5) or complete (n=2) response with a median response duration of 237 days. The median progression free interval in all 10 cats was 117 days and the median overall survival time was 324 days. Concomitant liposomal radiochemotherapy was tolerated well in nine cats, one cat experienced temporary anorexia. Although the number of patients is too small to make definitive conclusions, results appear promising enough to investigate the role of liposomal doxorubicin as a radiosensitizer further.