Importance and Risk Factors

Importance and Risk Factors

The guiding principle of cancer screening is that if a cancer can be found at a very early stage then morbidity or mortality from the cancer can be prevented by early treatment with possible cure. Almost all cancers are treatable if detected early enough and proper treatment is given in a timely fashion. Screening for cancer in the general population is based upon what cancers occur commonly. The most common cancers in adults in the United States are; breast, prostate, lung, colon, cervical, skin, bladder and non-Hodgkin lymphoma.

The most common cause of death from cancer is overwhelmingly from lung cancer. Also in the list of common causes of cancer deaths from less common cancers are ovarian and pancreatic cancers. For some cancers there is not a readily available screening test such as with ovarian or pancreatic cancer. That is why these types of cancers are sometimes referred to as “silent killers.” The major effort of public health initiatives for screening is to apply evidence based screening tests that are proven to decrease mortality from cancer as a result of the screening test.

Just as important as early detection and screening for cancer are, decreasing modifiable risk factors for cancer formation is a focus also.  Overwhelmingly, the biggest modifiable risk factor for cancer prevention is to target smoking cessation.  Lung cancer is the number one cancer killer and cigarette smoking is strongly associated with lung cancer and increases the risk of getting lung cancer greatly.  Another example of a modifiable risk factor is sun exposure and proper sunscreen use to help reduce skin cancerOther avoidable or modifiable risk factors include diet, infections and weight control.  A modifiable diet example would be the chewing of the betel nut which is common in areas of the world such as Papua New Guinea.  Exposure to toxins of this nut greatly increases the risk of cancer of the mouth.  Certain infections such as Hepatitis C increase the risk for cancer of the liver.

It is estimated that by the time a cancer is palpable (a tumor big enough to feel), it has been growing for several years.  Waiting for a cancer to cause symptoms is not very efficient as this usually occurs in later stages of the cancer.  Screening should be focused on the common cancers that can be treated early and thus have a beneficial effect on the natural history of the disease.

Some cancers can be detected in the “pre-invasive” stage. A cancer is defined by abnormalities in cells that cause them to develop abnormally and/or invade beyond their normal growth area or organ of development. When cells become abnormal but have not yet crossed the boundary of the basement membrane or invaded adjacent tissue, this is termed a pre-invasive cancer or carcinoma in-situ (CIS). Several common cancers have pre-invasive forms that are detectable.

Oral cancer may be detectable by a white plaque that develops on the mouth, lips, cheek or tongue known as leukoplakia. This may be felt by the person with the tumor and it can be seen by a doctor performing an examination. Someone with many years of smoking and alcohol abuse who visits a doctor should have examination and inspection of their mouth to look for these suspect lesions. In fact, dentists also look at the mouth for suspicious areas.

Skin cancers can also be readily screened for by a physician who is experienced in spotting skin cancers. It is common for older adults to develop many different types of skin lesions that are not skin cancer such as the stuck-on waxy or warty appearance of a seborrheic keratosis. An actinic keratosis, on the other hand, feels rough. Actinic keratoses are pre-cancerous and can generally be examined and treated by a number of methods such as cryotherapy (freezing) or topical medications. Suspicious moles or skin lesions that could be melanomas or other skin cancers need biopsy and/or excision for diagnosis.

Screening for pre-invasive lesions in the esophagus is possible via a test called endoscopy. Upper endoscopy is a camera that is passed through the mouth to look at the esophagus. If concerning areas are seen, biopsies can be taken at the same time. This would only be done in people at risk for esophageal cancer, which is not common in the US.

Screening for pre-cancers in the colon can similarly be done with colonoscopy. Screening for pre-invasive breast cancers is done in the same manner as screening for breast cancer, with breast examination and mammography. The key difference here is that pre-invasive lesions, by definition are not cancer yet and would not be palpable.

Screening for pre-invasive cancer of the cervix is commonly done with the Pap smear and tests for HPV. This can be followed with colposcopy and biopsy if there is evidence of abnormal cells.

When any of these screening tests are done and detects a pre-invasive cancer, the next step is usually to confirm the cancer and take a sample of the cancer cells or remove the tumor entirely. Sometimes this is done in stages (as with esophageal cancer or colon cancer) or the biopsy and diagnosis is done at the same time (as with many skin cancers).

In addition to screening for early cancers and avoiding risk factors for the development of cancer, another form of early prevention is to take a medication that reduces the risk of a future cancer forming. This type of therapy is termed chemoprevention. The best example of this is taking the medication tamoxifen in a woman at high risk for breast cancer.

Another form of risk reduction is to remove the target organ of a future cancer before it ever forms. For example, a man that has several brothers and father that all developed colon cancer in their early 40’s may desire to have his colon removed in his 30’s. This type of procedure would be termed a prophylactic colectomy. Similar strategies are applied to woman at very high risk for breast cancer (such as those with the BRCA-1 gene), they might undergo a prophylactic mastectomy.

All of these different types of strategies help to detect an early cancer, minimize morbidity from a cancer or even prevent it from occurring entirely. The exact strategy that is best for you should be discussed with your doctor based upon a detailed review of your personal risk factors.

REFERENCES:

  1. www.cancer.gov/cancertopics/screening
  2. apps.nccd.cdc.gov/uscs/toptencancers.aspx#All
  3. Carey WD. (2010) Cleveland Clinic: Current Clinical Medicine, 2nd ed. Section 14. Cleveland, OH: Saunders.
  4. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical Oncology, 4th ed. Chapter 26. Philadelphia, PA: Churchill Livingstone – Elsevier
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.