Cancer originates from alterations within our genes. These changes disrupt the instructions guiding cell growth and division. Normally, cells grow, divide, and die in an orderly fashion. When genetic instructions are disrupted, cells behave abnormally, leading to uncontrolled proliferation. This uncontrolled cell growth forms the basis of all cancers.
The Genetic Basis of Cancer Development
Cancer develops from specific genetic alterations called mutations. These mutations affect two main gene categories regulating cell growth and division. Proto-oncogenes act like a “gas pedal,” promoting cell growth and division when activated. When mutated, a proto-oncogene becomes an oncogene, like a gas pedal stuck “on.” This leads to continuous, unregulated cell proliferation and tumor formation.
Tumor suppressor genes function like a cell’s “brakes.” They normally slow cell division, repair DNA errors, and initiate programmed cell death for damaged cells. If these genes mutate, their function is compromised, removing the brakes on cell growth. This allows cells with damaged DNA to divide unchecked, accumulating mutations and driving cancer.
Hereditary vs. Acquired Gene Mutations
Cancer-related gene mutations are either acquired during a person’s lifetime or inherited from a parent. Acquired (somatic) mutations are most common, occurring in a single body cell after conception. These mutations are not in every cell and cannot be passed to offspring. Environmental factors, like UV radiation or tobacco chemicals, and errors during normal cell division often contribute to acquired mutations. Such mutations are confined to tumor cells, explaining why most cancers are not hereditary.
Hereditary (germline) mutations are present in the egg or sperm cell from which an individual develops. This means the mutation is in every body cell from birth and can be passed down. While inheriting such a mutation increases cancer risk, it does not guarantee cancer. Individuals are born with one “faulty brake” in every cell, making it easier for a second “brake” to fail later, initiating cancer.
Identifying Genetic Cancer Risk
Identifying genetic cancer risk often begins with genetic counseling. A trained professional reviews a person’s personal and family medical history. This assessment helps determine if cancer patterns suggest an inherited predisposition. Factors like early-onset cancers, multiple family members with the same cancer, or rare cancers indicate a higher likelihood of a hereditary mutation.
If family history suggests elevated risk, genetic testing may be recommended. This involves analyzing blood or saliva for specific inherited mutations in genes known to increase cancer risk. Common genes tested include BRCA1 and BRCA2 (breast and ovarian cancers) and genes linked to Lynch syndrome (colorectal and endometrial cancers).
Genetic test results fall into three categories: positive, negative, or a variant of uncertain significance. A positive result indicates a detected mutation, providing information about elevated cancer risk. A negative result means no known cancer-associated mutation was found. An uncertain variant indicates a genetic change whose impact on cancer risk is not yet understood. A genetic counselor interprets these results for personal health and family planning.
Managing Hereditary Cancer Risk
Individuals with identified hereditary cancer risk have various proactive health management strategies. One approach is enhanced cancer screening. This may include starting screenings earlier or undergoing them more frequently. For example, individuals with a BRCA1/2 mutation might begin mammograms or breast MRIs in their 20s or 30s, or undergo more frequent colonoscopies for Lynch syndrome.
Another strategy is chemoprevention, using risk-reducing medications. Certain drugs lower the risk of specific cancers in individuals with high genetic predisposition. For instance, some hormonal therapies can reduce breast cancer risk in women with BRCA1/2 mutations. These medications are considered based on the individual’s genetic mutation, health, and potential side effects.
Risk-reducing surgery is a more definitive option for some with very high hereditary cancer risks. Prophylactic procedures, like a bilateral mastectomy (breast cancer) or oophorectomy (ovarian cancer), are considered. These surgeries significantly reduce, but do not eliminate, the chance of developing cancer by removing at-risk tissues. The decision is personal and involves discussions with healthcare providers about benefits, risks, and quality of life.
Genetic Information in Cancer Treatment
Genetic information increasingly transforms existing cancer treatment. This involves analyzing acquired genetic mutations within a patient’s tumor, forming the foundation of personalized medicine in oncology. By sequencing tumor DNA, doctors identify specific genetic alterations driving its growth.
These identified mutations guide treatment decisions. If a tumor has a specific mutation making it reliant on a particular pathway, doctors select targeted therapies. These drugs block the mutated protein or pathway, halting cancer progression with fewer side effects on healthy cells. Examples include drugs targeting EGFR in lung cancer or HER2 in breast cancer.
Genetic analysis of tumors also helps predict cancer response to treatments, including immunotherapies. Genetic markers within a tumor can indicate if the patient’s immune system will respond to drugs that unleash its anti-cancer activity. This detailed genetic profile allows oncologists to tailor treatment plans, matching strategies to each patient’s tumor.