How can rapid growth cancer get nutrients in vivo?
Long back in 1971 Falkman and others put forward new therapeutic implications of targeting blood vessels supplying nutrients to tumors.   Treatment you are mentioning is called 'Anti-angiogenic therapy '. However current challenges in this therapy are resistance to antiangiogenic agents and non specificity. Plus there was huge 'normalization effect' which was actually helping other blood vessels around tumor. To answer your question, Cancer cell makes their own blood vessels instead relying on host machinery. There are many other factors also why this kind of treatment is not successful yet.