Australian researchers on Monday identified a defective gene, which explains why some colorectal cancer patients respond very well to radiotherapy but others not at all.
A team of Australian scientists from the Garvan Institute for Medical Research, have been investigating the tumor cells of over 200 colorectal cancer patients, and how they responded to their treatment.
They believe the outcome of treatment may depend on the gene MCC, which happens to be expressed at low levels in a subset of colorectal cancers.
According to Dr Laurent Pangon, the defective gene was a " double-edged sword", as it appeared to both encourage a tumor to develop but also make these less resistant and easier to kill off with radiotherapy.
"Our findings show that MCC appears to be involved at a kind of DNA damage checkpoint, when the cell recognizes that there is DNA damage and that it needs to do something to correct it," Dr Pangon told Australia Associated Press on Monday.
"If you lose MCC therefore you lose the ability of the cell to repair DNA damage ... and cancer would probably develop."
While surgical removal is the primary way to combat these cancers, patients can also undergo anti-cancer therapies to kill off any cancer cells left behind or tumors, which surgeons could not reach.
Dr Pangon said those patients with a defective MCC gene were found to have a much improved response to radiotherapy, and some types of chemotherapy, as their tumors were much less resistant to treatment.
"That is because those therapies kill cancer cells through inducing DNA damage and if the DNA damage response of the tumor is already defective, the therapies work better," he said.
"Our study has the potential to provide a scientific explanation as to why some patients respond to treatment better than others."
The researchers also developed a test which can identify those colorectal cancer patients who have the defective gene, and so those who do not and were best diverted to alternative therapies.
Dr Pangon said the study is part of the new frontier in cancer treatment, in which a patient's genetic make-up can point doctors to the anti-cancer treatment most likely to work.
The research is published online by the journal Genes and Cancer.