Clinical trials for spleen hemangiosarcoma in dogs:
http://www.petcancercenter.org/Clinical_Trials_Current_Dogs_Splenic_hemangiosarcoma.html
See the link for 3 different clinical trials, location, and contact info:

NEW YORK
–   Study: Combination Chemotherapy and Immunotherapy for Dogs with Splenic Hemangiosarcoma

PENNSYLVANIA
–   Study#1: Evaluation of the safety of a recombinant viral vector (AAV8) encoding an anti-VEGF antibody and its ability to delay tumor progression and prolong survival in dogs with splenic hemangiosarcoma
–   Study#2: Further Evaluation of the Benefits of a Traditional Chinese Medicine Supplement for Dogs with Splenic Hemangiosarcoma