For decades, scientists have been trying to get around the drug resistance that is characteristic of all cancers. Some say, not a single drug or combination of drugs has succeeded.
The assumption behind all the efforts has been the gene mutation theory of cancer. Mutated genes somehow either cause cancer directly or inactivate genes thought to guard against cancer, the so-called oncogenes and tumor suppressor genes. However, there is no functional proof that the gene mutation theory is correct.
The gene mutation theory of cancer hasn’t yet produced the types of breakthroughs we all want. Everyone in cancer research seems to have centered their attention on gene being the culprit. It would be expected that after more than a century of pursuing this one angle, and the numerous links that have been made, this should have lead to more progress than is presently observed.
Sequencing the genome of cancer cells is explicitly based upon the assumption that the pathways of tumor cells can be known in sufficient detail to control cancer, an assumption that some scientists believe to be false. The assumption that the pathways of tumor cells can be known in a patient with metastatic cancer is logically inconsistent with the reality of tumor cell evolution.
The problem is that a patient with metastatic cancer can have billions of unknown cancer cells disseminated throughout the body at unknown locations. Each cancer cell can be different. And the cancer cells that are present change and evolve with time.
There is another effort in research called the chromosomal theory of cancer. Even if cancers are from the same tissue, and are generated with the same carcinogen, they are never the same. There is always a cytogenetic and a biochemical individuality in every cancer.
http://cancerfocus.org/forum/showthread.php?t=3666