The objective of this study is to investigate the effectiveness of combining doxorubicin or carboplatin and temozolomide with propranolol in dogs with hemangiosarcoma. The use of either doxorubicin or carboplatin alone as a treatment for hemangiosarcoma has been studied, and studies with propranolol (historically used to treat heart disease) have shown promise as an added treatment against hemangiosarcoma, however, survival times still remain quite low. We are hopeful that survival times can be further improved using a combination approach to treatment, with combination of both intravenous and oral treatments. Dogs with hemangiosarcoma of the spleen, liver, heart or intramuscular region will be considered for inclusion in this study.