Researchers have updated an index used to predict a cancer patient’s chances of survival.

A report in JAMA Oncology looked at factors on the molecular level that could affect survival rates in people with lung cancer and with tumors that have spread from the lung to the brain. After analyzing data from almost 2,200 patients in various institutions, the researchers were able to pinpoint two genes that can help determine a patient’s chances. There was an existing database called the Diagnosis-Specific Graded Prognostic Assessment, and those findings have been incorporated to create a new index called the “Lung-moIGPA.”

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The update focuses specifically on lung cancer and associated brain metastases, tumors that have spread from the original affected site, because a metastasis to the brain is a serious and frequent result with lung cancer, particularly as lung cancer treatments have improved to help patients overcome those original tumors, the American Medical Association explains in a statement. “Understanding prognosis for lung cancer is important, both for designing individualized care and future clinical trials.”

The two gene alterations implicated in affecting these cancer patients’ survival are both involved in producing proteins that ultimately play a role in cell division and growth, according to the U.S. National Library of Medicine, the EGFR gene and the ALK gene.

Although the median survival rate in the group was 12 months, the AMA notes that while the study shows an association between those genes and survival rate, it “cannot establish causality.”

Lung cancer is one of the most common types of cancer, according to the American Cancer Society, accounting for 14 percent of new cancer cases. It is estimated that more than 158,000 people in the United States will die from lung cancer by the end of 2016. “Lung cancer is by far the leading cause of cancer death among both men and women; about 1 out of 4 cancer deaths are from lung cancer.”

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Source: Sperduto PW, Yang TJ, Beal K, et al. Estimating Survival in Patients With Lung Cancer and Brain Metastases. JAMA Oncology. 2016.