The Impact of Therapies on the Genomics of a Tumor

As genomic panels are completed, and genetic mutations are identified, providers can decide on a treatment plan which would target the specific tumor or cancer cell mutations. Those targeted therapies can be one of several approved cancer treatments—hormone therapies, therapies which block a blood supply to a tumor, therapies which try to kill or destroy specific cancer cells or even immunotherapies which try to trigger the patient’s immune system to destroy those cancer cells.

There are limitations to targeted therapies. Cancer cells can either resist the planned action of therapy or mutate so they find another pathway to continued growth.

You can liken the change to the change seen in viruses, for example what has happened with HIV. Over time, immune systems can learn how to stop cells from replicating, but viruses and certain cancer cells can adapt or evolve, making them resistant to the initial drug treatment. The cells survive because they have found a new pathway or mechanism to reproduce by mutation. In Canada, the mutation of the HIV virus has led to faster developing AIDS-related illnesses1.

Tumor cells can show mutations in a single cell, in an entire tumor or in mutations per megabase (or an area of the genome equal to the length of 1 million bases—the chemicals that serve as the building blocks of DNA)2. The number of mutations is being considered as to whether or not it is an indicator of a response to treatments.

One of the biggest challenges facing researchers and providers is identifying who will respond to therapy, and if they can see any indications that specific patients (based on biomarkers) will show a resistance or even genetic mutations after therapy.

As therapies result in changes to a person’s immune system, longitudinal studies or real-world data will be needed to show that those changes don’t increase the possibility of other, possibly deadlier, cancer cells to grow.

Increased education on the understanding of these biomarkers is necessary to make decisions on a single or combination of treatment therapies for cancer.

 
  1. https://www.theglobeandmail.com/canada/article-study-finds-mutated-strains-of-hiv-in-saskatchewan-causing-quicker/
  2. https://www.bms.com/assets/bms/us/en-us/pdf/Disease-State-Info/tmb-101-fact-sheet.pdf