From disease detection to predicting the most effective medication

Posted September 22, 2016By Tania Haas, Staff Writer

Allison Hazell, MSc, CCGC, CGC, Director of Genetics, led this Medcan seminar on September 15, 2016.

Participants learned that policies, laws and clinical expectations are adapting as genetics furthers the reach and depth of individualized medicine. Hazell distinguished between trusted genomic technologies – and those areas to consider with caution.  She also offered helpful context to media coverage of genetics, as well as the role of hereditary cancer panels and pharmacogenomics. The future role of liquid biopsy in disease detection was also addressed.

Some key takeaways are below as well as the complete online seminar with a Q&A session.

Today’s hereditary cancer panels: greater yield, lower cost

A gene panel is the simultaneous evaluation of several genes from different locations in the genome. Often the genes on a gene panel will relate to a single condition or a family of similar conditions. Hazell made the distinction between common and hereditary cancers. (Common cancers make up around 90% of all diagnoses while hereditary cancers are around 5 to 10% of diagnoses.) The most common hereditary cancer is due to mutations in breast cancer genes called BRCA1 and BRCA2.

“If I am working with someone who has a family cancer and it looks like a suspicious hereditary cancer; then we are trying to find the genetic mutation that is responsible for the cancer in the family. It’s really like looking for a needle in a haystack,” said Hazell.  “In the past, we had very targeted testing focused on a specific area. Today’s panel testing enables a more broad efficient testing of the genome, resulting in  greater coverage and yield.”

She adds that other benefits include reduced cost, more comprehensive data and it avoids the need for gene-by-gene testing and/or reflex testing.

Shifting paradigm: universal early detection

Hazell highlighted the evolution of genetic testing by quoting Marie Claire King, the geneticist credited with discovering the BRCA gene mutations.

“Right now we choose who to test based on family history or a significant risk of cancer.  Advocates like King argue that to identify someone as a carrier only after she develops cancer is a failure of cancer screening and cancer prevention,” said Hazell. “Her radical proposal is that every woman at age 30 is screened in order for early detection and prevention.”

Importance of pre-test counselling

A common question regarding specialized genetic testing is ‘Why not do more testing? Isn’t testing more genes better?’  Hazell spoke to how, when it comes to genetic testing, more is not always necessarily better. There is a lot to consider when digging into the genome, and that’s why the pre-test counselling piece is really important part of the process.

“It’s not as easy as testing everyone for everything. There are a lot of things to consider , and people will make different decisions based on their situation and/or preferences.”

Pharmacogenomics: improving the efficacy of medication

Pharmacogenomics can reduce trial-and-error prescribing by predicting which medications and dosages may be most effective.

“It provides an important piece of information that physicians can use when considering medication choice and/or dose,” said Hazell, who noted that it does not replace clinical judgment by any means. “The physician still takes into account traditional factors in decision-making.”

Pharmacogenomics requires team-based approach to medicine, with team members including the genetic counsellor, the primary care physician, the specialist (when needed) and the pharmacist.

Variation in medication response

While other factors like age, body mass or drug interactions can influence the response to or effect of medications, genetic factors can account for up to 95% of drug-response variability and susceptibility, according to Hazell.

The study of the genetic basis of drug response can reveal individual differences in: absorption or distribution, metabolism and excretion.  At this time, pharmacogenomics can predict responses to over 200 medications.

Post-cancer monitoring with liquid biopsy

Liquid biopsy is a non-invasive blood test to detect circulating tumour DNA. It is currently being used as a tool for post-cancer monitoring; for detecting the effectiveness of cancer treatment; and/or the recurrence of cancer in an individual However, there is a lot of excitement about the potential future applications of lipquid biopsy as population-based screen for early cancer.

Click here for the 30-minute online seminar.