Cancer Facts General Info
What is cancer anyway?
Cancer is not one disease, but rather a group of diseases that have two main things in common:
- The presence of abnormal cells that have
- lost their usual function and
- divide uncontrollably.
The scientific terms for this loss of normal cellular function and cell division are de-differentiation and proliferation, respectively.
- The failure of normal internal host mechanisms that typically protect the body and rid it of such abnormal cells.
Cancer prevention strategies can prevent the abnormal cells from developing and growing and/or maintain or improve the fidelity of our protective host mechanisms.
How does cancer start?
Any cell in the body has the potential to become a cancer. The changes that a normal cell goes through to become a cancer cell is call transformation. The process by which a normal cell transforms into a cancer cell is called carcinogenesis. Carcinogenesis occurs in 3 phases: initiation, promotion, and progression.
Initiation is the first step in carcinogenesis. Initiation is characterized by an insult to a cell that results in an irreversible genetic mutation, typically in a gene that influences differentiation and/or proliferation. Example initiating insults include exposure to cancer causing agents, or carcinogens. In addition, it is possible to inherit a mutation that carries a predisposition to cancer development, such as in an oncogene (normal state is off, and mutation turns it on) or a tumor suppressor gene (normal state is on, and mutation turns it off).
Promotion is a reversible phase that is influenced by various mechanisms that alter gene expression. Typically, such mechanisms involve more than the DNA itself, and include interactions between the DNA and other proteins in the cell. Collectively, these mechanisms are often referred to as epigenetics.
|Progression is the final phase of carcinogenesis and is characterized by malignant growth. Some environmental exposures, for instance hormones, can feed this growth. There are several host mechanisms that can protect from such growth progressing, such that we can co-exist with small non-invasive cancers within us without significant danger to our lifespan or quality of life.|
How does cancer spread?
Once a normal cell has transformed into a cancer cells, and those cancer cells have started to divide to form a malignant tumor, there are two additional phases that characterize a cancer:
Invasion – Malignant, or cancerous cells are not themselves life threatening. It is only when they acquire the ability to invade surrounding tissues that a cancer begins to cause trouble. They can erode into surrounding structures within the body or they can follow blood, lymph, or nerve tracts to spread to different organs.
Before this step, pre-invasive lesions occur along a spectrum:
Dysplasia (or atypia) – These cells are a very early form of precancerous cell that may or may not ever develop into a cancer. This is equivalent to the part of the figure above that correlates to the promotion phase of carcinogenesis.
Intraepithelial neoplasia (or in-situ tumor) – These cells are fully malignant but have not acquired the ability to invade surrounding tissues. This is equivalent to the last portion of the figure above, at the end of the progression phase of carcinogenesis. In-situ tumors are also sometimes called precancers.
Metastasis – Metastasis, or cancer spread, can occur regionally via the lymphatic system to regional lymph nodes. Distant metastasis occurs through the bloodstream. The most common organs that cancers spread to include bone, liver, lung, and brain.
Invasion and metastasis form the basis of the Stages of Cancer. While staging differs between different types of cancer, in general, cancers that are not yet invasive are called Stage 0, cancers that have metastasized to lymph nodes are Stage 3, and cancers with metastasis into distant organs in the body are Stage 4.
Generally, the earlier the stage at diagnosis, the better the prognosis, or likelihood of long-term cure. This is why we emphasize proper risk-based cancer screening. Such screening can lead to earlier detection and better outcomes, if a cancer does occur.
Where does cancer start?
Cancer can start in any place in the body. Where it starts, not where it spreads to, dictates the cancer type. This is because the originating cell type influences its biologic behavior. For instance, some cancer types are typically indolent, or slow growing, and others tend to be aggressive. Patterns of spread also differ by where the cancer originates.
The most common cancers in both the U.S. and the world are breast, prostate, lung, and colorectal. These four cancers comprise more than 50% of all cancer diagnoses. The 5th and 6th most common cancers vary between the U.S. and the rest of the world. In the U.S., they are gynecologic (particularly uterine) and skin cancers, respectively. In the world, they are stomach and gynecologic (both uterine and cervical) cancers, respectively. This is according to 2016 Global Burden of Disease statistics compiled by the Institute for Health Metrics and Evaluation (IHME). Each of these cancers have different risk factors, different presenting symptoms, and different screening and prevention approaches. Please see our specific cancer fact sheets to learn more about each of these cancer types.
How does cancer persist?
As mentioned above, our bodies have several natural mechanisms that protect us from cancers developing and spreading. Below are just a few.
The Proofreader and The Eraser: Our cells have DNA repair mechanisms that proofread for genetic mutations, and if one is found, cut them out and correct the DNA back to its prior code.
The 007: Our cells are internally programmed to self-destruct if it detects an abnormality within it. This Bond-like feature is called Apoptosis.
The Clean Up Crew: Our bodies have a whole family of cells, including cytotoxic T-cells, dendritic cells, and natural killer cells, that coordinate Immune surveillance for the presence of abnormal cancer or pre-cancer cells. Working together, they can detect and then clear individual cancer cells from the body.
There are also several mechanisms that cancer cells use to trick our bodies to help them grow:
The Enablers: Cancer cells cannot survive unless they are surrounded by other cells that allow them to grow. The cells that form this cozy environment for cancer formation and growth, called the Tumor microenvironment, include fibroblasts and pericytes.
The Seductress: A malignant tumor cannot grow beyond a millimeter in diameter unless it can attract blood vessels to grow toward it to deliver oxygen and nutrients to support its growth. This process is called Neovascularization and can be counteracted by Anti-angiogenesis.
What are specific risk factors for cancer?
While some types of cancer tend to occur in childhood or young adulthood, in general, cancer risk increases with age. The reason for this general trend is because our protective host mechanisms tend to become less effective as we age. However, it is important to remember that cellular age can be much younger than chronologic age, if we take good care of ourselves.
Gender differences in cancer can occur due to differences in the presence of tissue (for instance, only women can develop ovarian or uterine cancer, and only men can develop prostate cancer), the volume of tissue (eg. men can develop breast cancer, but it is much more rare than in women), and differential hormonal interactions with environmental carcinogens (eg. obesity and poor diet are major risk factors for colorectal cancer (CRC), but men have a higher risk of developing CRC than women).
Socioeconomic differences and access to health care play a role in cancer frequency. In addition, some hereditary forms of cancer are more frequently found in certain subpopulations (eg. hereditary breast and ovarian cancer associated with BRCA mutations occur more frequently in Ashkenazi Jews).
These are quite numerous and vary by cancer type. The lifestyle choice that causes the highest number of cancer cases is tobacco use. Chronic and/or heavy smokers not only have a high risk for lung cancer, but also have an increased risk for head and neck cancers and gastrointestinal cancers. The second most impactful lifestyle risk factor includes overweight and obesity, which is associated with 13 difference cancers. Unprotected sex and other high-risk behaviors can lead to viral infections that are associated with certain cancers (eg. HPV, HIV, hepatitis). And some cancers are associated with exposures to environmental toxins. Other lifestyle risk factors amenable to behavior modification include poor diet, physical inactivity, and more than modest alcohol use.
PERSONAL MEDICAL FACTORS
Some medications have been associated with an increased risk of certain cancers, as well as high dose radiation. In addition, because of a phenomenon known as the field effect, cancer survivors have an increased risk of have a new unrelated cancer in the same organ (eg. breast cancer survivors sometimes find a new cancer in the opposite breast, and colorectal survivors have a higher risk of developing another cancer in a different part of the colon). Lastly, the finding of dysplasia on pap smear or in-situ lesions on biopsy is associated with an increased risk of cancer.
FAMILIAL AND GENETIC FACTORS
Families share both genes and environments. In addition, cancer associated behaviors tend to cluster within families. Therefore, not all family history is significant when considering the potential for hereditary cancer risk. However, certain family history patterns can suggest the presence of a hereditary syndrome.
Hereditary cancers generally account only for 5-10% of cancers. Genes can still be involved in sporadic, or non-inherited cancers, but instead of mutations in high susceptibility genes, they are due to variants in single base errors that influence how our bodies interact with our environment.
However, it is important to identify significant family history, because most hereditary cancer syndromes are associated with an increased risk of several different cancers. This makes individuals who carry the associated genetic mutations eligible for special cancer screenings and highly effective medical and surgical interventions for risk reduction. Yet, unfortunately, the vast majority of individuals with hereditary cancer risk are unaware of their syndrome until after they are diagnosed with cancer, which doesn’t allow them the opportunity for prevention. Therefore, it is important for individuals with a family history of cancer to seek the expertise of a health care professional with training in cancer genetics, who can examine the family pedigree for patterns suggesting a hereditary syndrome, which is usually associated with a high risk for more than one cancer, instead of clustered environmental exposures, which is typically associated with a moderately increased risk for just the index cancer.
What is your best next step?
As complex human beings, often we have a complicated mix of risk factors. To add to that complexity, two individuals with identical risk profiles will often make different risk reduction choices, based on their own risk tolerance and personal preferences.
A 1:1 Cancer Risk and Prevention consultation will help you tease out your personal history, discover what your risks actually are, and what are your options for living your healthiest, happiest, and longest life. Then, you will be empowered to make well-informed decisions about how you would like to proceed, empowered to take charge of your health! And, because we understand the gap between knowing what to do and actually doing can sometimes be wide, we even offer health coaching support to integrate healthy habits into your busy life.
- To schedule your consultation today, go here.
- If you would like to take our FREE cancer risk self-assessment first, go here.
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To your health!
P.S. Medical references for any of the materials contained in this fact sheet are available upon request. Please note that this information is provided for general educational purposes only and cannot substitute for personalized medical advice