Finally, cancer is an incredibly heterogeneous disease. Not only is each site different, but each individual cancer is markedly different (e.g. an adenocarcinoma which is not EGFR/Alk mutated has a much worse prognosis than an adenocarcinoma with such mutations). Therefore, there will never be a universal cancer cure (barring the introduction of micromachine nanobot assassins, which will put all procedure based specialties out of business). Furthermore, cancer is a micro-evolutionary process and is ever adapting to therapy. The sure fire ways to "kill cancer" to obtain a cure are to surgically remove it or irradiate the bejesus out of it. In 99% of cases where Medical Oncologists have touted a chemo or small molecule "cure" the cancers come back as more resistant. Case in point is imatinib.