Following your diagnosis of cancer, your reaction may be one of shock and disbelief. If you have been told that chemotherapy or radiation therapy are an important part of your treatment, many unpleasant images may come to mind. But as you move beyond that initial shock to begin the journey of surviving your cancer, you have good reason to be optimistic. Medicine has made—and continues to make—great strides in treating cancer and in making cancer treatment more personal and tolerable. The greatest recent advances are in Precision Medicine.
It’s safe to say that precision medicine is now considered one of the pillars of cancer therapy, joining the three longstanding pillars or surgery, radiation therapy and chemotherapy.
Treating Abnormalities That Are Cancerous
It is now understood that most cancers result from abnormal genes or gene regulation. The cause of these changes can be environmental, spontaneous, or inherited. By identifying the genomic changes and knowing which genes are altered in a patient, cancer drugs that specifically attack that gene (or the later consequences of that gene) can be used to target the cancer and avoid the more general side effects of chemotherapy.
Because precision cancer medicine seeks to define the genomic alterations that are driving a specific cancer, rather than relying on a simple broad classification of cancer solely based on its site of there is no longer a “one-size-fits-all” approach to cancer treatment. Even among patients with cancer originating in the same tissue or organ, the behavior of the cancer and its response to treatment can vary widely.
The idea of matching a specific treatment to an individual patient is not a new one. It has long been recognized, for example, that hormonal therapy for breast cancer is most likely to be effective when the breast cancer contains receptors for estrogen and/or progesterone. Testing for these receptors is part of the standard clinical work-up of breast cancer. What is new, however, is the pace at which researchers are identifying new tumor markers, new tests, and new and more targeted drugs that individualize cancer treatment. Tests now exist that can assess the likelihood of cancer recurrence, the likelihood of response to particular drugs, and the presence of specific cancer targets that can be attacked by new anti-cancer drugs that directly target individual cancer cells.
Genomics vs Genetics
Genomic tests are used to identify the specific genes in a cancer that are abnormal or are not working properly. In essence, this is like identifying the genetic signature or fingerprint of a particular cancer. Genomic testing is different from genetic testing. Genetic tests are typically used to determine whether a healthy individual has an inherited trait (gene) that predisposes to a specific health condition.
How Does Precision Cancer Medicine Work?
The purpose of precision cancer medicine is not to categorize or classify cancers solely by site of origin, but to define the genomic alterations in the cancers DNA that are driving that specific cancer.
Precision cancer medicine utilizes molecular diagnostic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. Once a genetic abnormality is identified, a specific targeted therapy can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells. Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed.
What’s Normal?
Normal cells have control systems that allow them to replicate only as needed for growth – in children, for example – or to replace damaged or worn-out cells. Most normal cells are firmly anchored to one area of the body, such as the lung or the breast. When damage to a cell cannot be repaired or when a cell reaches the end of its useful life span, it is programmed to die, a process called apoptosis.
What’s Not Normal?
Cancer cells don’t follow these rules. Gene mutations, chromosome alterations, and changes in other molecules enable them to replicate endlessly, ignoring signals ordering them to self-destruct, and to migrate to distant sites in the body, such as the bones, liver, or brain, where they set up satellite tumors. Usually, several genomic abnormalities are driving the cancer, but these can be different in different cancers that otherwise seem to be the same. Two people with the same type of lung cancer, for example, may not respond to treatment in the same way if their cancers are driven by different combinations of mutations.
Cancer-driving abnormalities may occur spontaneously (de novo) or be passed from parent to child (hereditary). Spontaneous changes happen all the time – thousands of times a day in single cell – often due to DNA damage caused by factors like sunlight, diet, or smoking. Some abnormalities are harmless, some cause the cell with the mutation to die, and some are fixed by the body’s elaborate repair mechanisms or are eliminated before cell replication occurs. A very small minority of these changes, however, can evade repair and alter the cell in a way that, rather than die, develops an improved ability to grow or survive. These alterations lead to cancer or predisposes them to developing cancer. Genomic tests evaluate the genes in a sample of diseased tissue (cancer) from a patient who has already been diagnosed with cancer. In this way, genes that have mutated, or have developed abnormal functions, are identified in addition to those that may have been inherited.
Further Reading and Other Resources
Liquid Biopsies Find Distinct Genomic Profiles in Most Patients with Carcinoma of Unknown Primary
Liquid Biopsy Can Help Predict Outcomes in Metastatic Triple-Negative Breast Cancer
Tissue Agnostic – Genomic Based Treatment – A Paradigm Shift in Cancer Treatment
Precision Cancer Medicine Offers Hope for Treating Rare Cancers
