BOSTON (Reuters) – Doctors have identified two genetic mutations that control the growth and development of malignant gliomas, a particularly deadly and difficut-to-treat type of brain tumour.

The discovery opens the possibility of helping to distinguish between two subtypes of particularly deadly gliomas, known as primary and secondary glioblastoma multiforme, and may point the way to new treatments for the cancer – the same type affecting US Senator Edward Kennedy, the doctors said last week.

The mutations also may help predict which patients will live longer, the researchers reported in the New England Journal of Medicine.

Patients with mutations in either of the genes, known as IDH1 or IDH2, tended to survive an average of 31 months compared to 15 months for glioblastoma patients whose tumours lacked either mutation.

"All GBMs are basically considered the same and are treated in the same way. Our studies clearly demonstrate that we need to start thinking about them as different," Dr. Hai Yan of Duke University in North Carolina, who worked on the study, said in a statement. "The results are so clear cut. I have been doing intensive genetic studies in brain cancers for six years, and I have never seen gene mutations as striking as in this study."

The findings were based on samples from 445 brain tumours that were compared with 494 cancers from outside the nervous system.