This is a type of cancer treatment? imatinib mesylate?

Yes it's cancer drug: Imatinib is an oral tyrosine kinase inhibitor- used to treat CML and other cancers of the blood cells. Imatinib is also used to treat gastrointestinal stromal tumors (gist; a type of tumor that grows in the walls of the digestive passages and may spread to other parts of the body). Imatinib is also used to treat dermatofibrosarcoma protuberans when the tumor can't be removed surgically.

Yes, CML & GIST: This drug, gleevec, (imatinib) is used for treatment of chronic myeloid leukemia and gastrointestinal stromal tumors.