Patients with breast cancer, lung cancer and chronic lymphocytic leukemia (CLL) who have the CYP3A7*1C allele of the CYP3A7 gene experience worse outcomes than those without the allele.1  

The CYP3A7 gene encodes enzymes that metabolize endogenous hormones as well as chemotherapy agents. The gene is typically only active during infancy, but it is switched on in some people in adulthood. Patients with the CYP3A7*1C allele may metabolize chemotherapy agents differently, resulting in the outcomes, according to researchers. .

“Identifying genetic variants that are associated with outcome could be important for 2 different reasons: prognostic and predictive,” Olivia Fletcher, PhDsenior investigator at the Breast Cancer Now Toby Robins Research Center at The Institute for Cancer Research, London, United Kingdom told Cancer Therapy Advisor.

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“The overall treatment that a woman receives for breast cancer is determined by her risk of recurrence based on a number of standard prognostic indicators…. Finding additional prognostic indicators – including genetic variants – may help to refine this process and allow clinicians to select treatment plans that are optimized for particular risk levels,” she said.

“’Predictive’ refers to selection of particular treatment types. Again, we would hope that identifying particular genetic variants that are involved in drug metabolism or involved in determining tumor characteristics might inform decisions about which treatments would be optimal for which patients,” she added.

Dr Fletcher and her colleagues analyzed DNA samples from 1008 patients with breast cancer, 1128 patients with lung cancer, and 347 patients with chronic lymphocytic leukemia (CLL) for the single nucleotide polymorphism (SNP) rs45446698, which is one of the SNPs unique to the CYP3A7*1C allele. A total of 73 breast cancer patients, 89 lung cancer patients, and 23 CLL patients were carriers of the allele.

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Patients with breast cancer who had the the allele demonstrated a 74% increased risk for disease-specific mortality, and patients with demonstrated a 43% increased risk of all-cause mortality; patients with CLL who had the allele demonstrated a 62% increased risk for disease progression.