Immunotherapy is more powerful than this because it is a new paradigm for treating cancers, that adapts to their changing mutations.
The current therapy that is showing broad spectrum efficacy is “checkpoint inhibitors.” What Is a Checkpoint Inhibitor? Immune Checkpoint Inhibitor Definition Unlike most cancer drugs, these work on the healthy immune cells, not on the cancer itself, so this reduces the ability to escape its effect.
After that is promising results from personalized cancer vaccines (based on neoantigens). http://www.sciencemag.org/news/2015/04/personalized-cancer-vaccines-may-fight-tumors Here, again, the target is healthy immune cells, that have the ability to adapt as the cancer adapts to automatically learn the new antigens that arise.
Of course, there is reason to hope these approaches will work synergistically together, and with other approaches like chemotherapy and radiation therapy. It is important to recognize that this is a fundamentally new approach to treating cancer, and it is seeing real efficacy in patients already.