In preliminary findings from an ongoing study, researchers at Mayo Clinic have identified four different factors they say predicts long-term survival in patients diagnosed with lung cancer, and one of the strongest is inheritance of a gene variant, GSTM1 positive, which is more efficient than another allele type of the GSTM1 gene at detoxifying carcinogens.
They found that patients with a null type at this gene were four times more likely to die within two years as were matched patients who had the positive variant.
The researchers also found that patients who had surgery, who were active, and whose cancer did not come back or progress were much more likely to survive five years or longer.
"Outcome varies among lung cancer patients, even within groups that have the same stage at the time of diagnosis, and so it is difficult to know how aggressively to treat and provide follow-up care for individual patients," said the study's lead investigator, Ping Yang, M.D., Ph.D., a clinical and genetic epidemiologist at Mayo Clinic.
"In order to enhance both survival and quality of life, we are trying to establish a model that will identify patients who would benefit from additional clinical intervention, and the data we have accumulated to date could be enormously helpful," she said.
To derive these predictive factors, the researchers aim to compare 400 lung-cancer patients treated at Mayo Clinic and who have survived five or more years, with 400 patients who lived less than two years after treatment. The researchers match the groups by age at diagnosis, gender, tumor cell type, cancer stage and the number of primary lung cancers, and they examine blood samples and follow the progress of the patients' disease as well as their quality of life.
In an interim analysis of data on 150 patients in each group, the researchers specifically found that patients who experienced any progression or recurrence of their cancer were almost three times more likely to die within two years, compared to patients of the same cancer stage whose disease did not progress or return.
They also concluded that lung cancer patients who had surgery were three times as likely to have longer survival as matched patients who did not have surgery. "This can be very useful information for patients who are undecided about whether they should risk having surgery," she said.
Patients who reported being "unable to do work or could only do light work" were at a 2.7-5.8 fold higher probability of dying within two years than were patients who were active, the researchers also discovered. "The clinical care of these patients is a long- term process," Yang said. "If, through follow-up and monitoring, we find a patient is physically inactive, we may recommend exercise and rehabilitation as appropriate to keep them stronger."
Knowing the contribution of inheriting a GSTM1 gene form to outcome is also important, she said. "If our model tells us that a patient's cancer has a higher chance of recurring or progressing because of innate genetics in metabolism, we can watch them more closely, and consider treating them aggressively and promoting preventive measures," Yang said.
The GSTM1 gene is just one of many candidate genes the investigators are studying in these patients.
Materials provided by American Association For Cancer Research. Note: Content may be edited for style and length.
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