Information about the prevention of cancer and the science of screening appropriate individuals at high-risk of developing cancer is gaining interest. Physicians and individuals alike recognize that the best “treatment” of cancer is preventing its occurrence in the first place or detecting it early when it may be most treatable. Skin cancers, which include basal cell carcinoma, squamous cell carcinoma and melanoma, occur more commonly than any other type of cancer. In general, basal cell carcinomas and the most common squamous cell carcinomas are related to chronic sun exposure and are cured by surgical removal. Melanoma is a potentially fatal type of skin cancer that begins in the melanocytes, which are the cells that are responsible for skin color.
The incidence rate of melanoma has been climbing steadily since the early 1970s. In 2003, the American Cancer Society estimated 54,200 cases of melanoma with 7,600 deaths related to the disease. Although melanoma can be successfully cured in its early stages, it is the most common fatal form of skin cancer, accounting for more than 79% of all skin cancer–related deaths. The chance of an individual developing cancer depends on both genetic (inherited) and non-genetic (environmental) factors. Non-genetic or environmental factors may include diet, exercise, or exposure to other substances present in our surroundings. An example of an environmental factor that is known to play a role in facilitating the process of healthy cells turning cancerous is the relationship between tobacco smoking and lung cancers. Other cancers have no known environmental correlation but are known to have a genetic predisposition. A genetic predisposition means that a person may be at higher risk for a certain cancer if a family member has that type of cancer. Melanoma results from a combination of environmental factors (exposure to ultraviolet light) and genetic factors.
Heredity or Genetic Factors
Approximately 10% of individuals diagnosed with melanoma have a family history of the disease. The vast majority of these patients have only one or more affected close relatives, which translates to only a small increase in the risk of developing a melanoma. Those at highest risk for developing melanoma are members of rare melanoma-prone families in which there are usually 3 or more affected members in 2 or more generations on the same side of the family. These family members are generally characterized as having multiple melanomas in the setting of dozens of atypical moles. The risk of developing melanoma in members of melanoma-prone families is estimated to be around 50% by age 50. By studying these families, researchers have discovered that the DNA of certain genes is often damaged in melanoma cells. Forty percent of melanoma-prone families have an alteration in the gene, CDKN2A, which is a gene that is normally involved in regulating normal cell growth. Research is ongoing to further define the role of CDKN2A in the development of melanoma.
Xeroderma Pigmentosum (XP): Xeroderma pigmentosum (XP) is a rare, inherited skin disorder characterized by extreme sensitivity to ultraviolet light. Individuals with XP have a genetic defect that prevents the repair of sun-induced damage to DNA. As a result, individuals with XP have a 1000-times higher risk of developing skin cancer than the general population. Almost half of individuals with XP develop a skin cancer by the age of 8 and the condition shortens life expectancy by over 30 years.
Environmental or Non-Genetic Factors
Although the causes of melanoma are poorly understood, researchers have identified some risk factors that are associated with melanoma.
Moles (Nevi): Most people have moles and most moles are harmless. Generally, moles develop in children and teenagers and increase in size slightly over time to a maximum diameter of 2 mm or so and remain the same size, shape and color for many years. Normal moles are usually evenly colored brown, tan or black spots on the skin that are round or oval and flat or raised. Atypical moles often called “dysplastic nevi” are defined as moles with a diameter of 5 mm or larger, with an irregular shape and variable color. It is not uncommon to have one or several atypical moles over the extremities or truncal regions. However, about 2% of the population is estimated to have Atypical Mole Syndrome (AMS), which is characterized by the presence of large numbers of moles and atypical moles (100 or more) or moles located on unusual sites (ears, scalp, buttocks, or feet). The lifetime risk for developing melanoma in the U.S. population is estimated to be about 1%. Patients with AMS have a slightly increased risk of developing melanoma (6-10%), which is lower than patients who belong to melanoma-prone families. Melanoma can often be recognized by applying the ABCD rule:
- Asymmetry: The mole is asymmetrical.
- Border Irregularity: The mole has ragged edges.
- Color: The mole is not evenly colored. It may have differing shades of tan brown, black, red, blue or white.
- Diameter: The mole is bigger than 6 millimeters, although some melanomas may be smaller.
A biopsy should be performed on any pigmented lesion that undergoes a change in size, shape or color.
Fair skin: Melanoma is more common in individuals who have fair skin and red or blond hair. With their fair complexions, these individuals tend to burn easily, placing them at a higher risk for developing melanoma. In addition, white people have a 20-times higher risk of developing melanoma than black people because they lack the protective effect of dark skin pigment. However, melanoma can develop in individuals with dark skin.
Ultraviolet (UV) Radiation: UV radiation has been recognized as a major environmental risk factor for melanoma. Sunlight and tanning lamps are sources of ultraviolet radiation. In fact, excessive exposure to the ultraviolet rays of the sun may account for two-thirds of all melanoma cases. Melanoma is more common in individuals who live in areas with greater exposure to UV radiation, such as Australia, New Zealand, Hawaii and California. There has been controversy regarding artificial tanning beds and whether the ultraviolet rays from these beds further increases the risk of melanoma. Several studies have suggested that more than 10 hours of exposure to a sunlamp/sun bed increases the risk of melanoma. However, given the delay between exposure and cancer development this is difficult to prove. The bottom line is that there is good data to suggest that exposure to tanning beds may provide exposure to dangerous levels of UV radiation and that over the next several decades there will be a dramatic increase in melanoma cases related to this hazardous agent.
Weakened Immune System: Individuals with weakened immune systems are at an increased risk of developing melanoma. This includes individuals who have been treated with medicines to suppress the immune system following an organ transplant and individuals who have AIDS or certain types of cancers that weaken the immune system.
Severe Sunburns: Individuals who have had one or more severe, blistering sunburn, especially as a child or teenager, are at an increased risk for developing melanoma. The risk of melanoma is greater for individuals who have had occasional but intense UV exposure than for those who have had consistent but lower level UV exposure, even if the overall UV dose is the same. Although sunburns during adult years are damaging, research indicates that 50-80% of the skin’s lifetime sun damage occurs during childhood or adolescence.
History of Melanoma: The risk of developing a second melanoma in a patient who has had a previous melanoma is estimated to be 3-7% or about 0.25% per year lifetime risk.
Two-thirds of cancer deaths in the U.S. can be linked to tobacco use, poor diet, obesity, and lack of exercise. All of these factors can be modified. Nevertheless, an awareness of the opportunity to prevent cancer through changes in lifestyle is still under-appreciated. The best way to reduce the risk of developing melanoma is to avoid known risk factors.
Reduce UV Exposure: Two-thirds of melanoma cases are directly associated to UV radiation exposure. In order to reduce the risk of developing melanoma, it is important to limit exposure to UV radiation and avoid severe sunburns. The UV rays of the sun are strongest between 10 a.m. and 3 p.m. One way to reduce exposure to UV radiation is to remain indoors or seek shade during this part of the day. In addition, individuals can protect their skin by covering up with long-sleeved clothing, hats and sunglasses.
Sunscreens with a sun protection factor (SPF) of 15 are considered to be adequate for normal people under most conditions. However, some recommend higher SPFs, such as 20-30, to compensate for uneven application by the typical users. It is important to note that sunscreen only reduces the amount of UV exposure, but does not prevent melanoma altogether. Sunscreen should not be used as an excuse to prolong sun exposure. Individuals who use sunscreen to extend their time in the sun expose themselves to the same amount of UV radiation as if they had remained outside for a shorter period of time without sunscreen.
Artificial tanning devices are best avoided, as a growing body of evidence indicates that they emit UV radiation that can damage the skin and increase the risk of developing melanoma.
Because 50-80% of the skin’s lifetime sun damage occurs during childhood and adolescence, it is imperative that parents take appropriate precautionary measures to adequately protect their children from excessive sun exposure.
Currently, the American Academy of Dermatology recommends the following measures: use of a broad-spectrum sunscreen with an SPF of 15 or greater; use of sunscreens for any sun exposure of more than 20 minutes; application of sunscreens 15 to 30 minutes before sun exposure; particular attention to the face, ears, hands, arms, and areas not covered by clothing; reapplication of sunscreen every 2 hours, using approximately 1 ounce for exposed areas; and use of hats and other protective clothing in addition to sunscreen for adequate protection.
Screening and Early Detection
For many types of cancer, progress in the areas of cancer screening and treatment has offered promise for earlier detection and higher cure rates. The term screening refers to the regular use of certain examinations or tests in persons who do not have any symptoms of a cancer but are at high risk for that cancer. The primary risk factors for melanoma are: (a) members of melanoma-prone families; (b) presence of atypical mole syndrome, (c) history of previous melanoma, (d) fair skin / blue eyes / red hair, (e) history of blistering sunburn, and (f) numerous moles.
When detected early, most melanomas can be cured with surgery alone. Individuals with and without risk factors should check their own skin for changes in order to detect melanoma early when it is most treatable.
Self-Exam: It is currently recommended that individuals check their own skin about once a month. This is especially important for individuals who have any of the risk factors for melanoma. During a self-exam, individuals should use a full-length mirror to familiarize themselves with the pattern of moles and other blemishes on their skin. It is important to notice any new moles or changes in the size, shape or color of existing moles. Individuals who perform self-exams consistently should notice any changes that occur on their skin and notify their physician immediately.
Routine checkup: It is currently recommended that individuals between the ages of 20 and 40 have a cancer-related checkup every three years and that individuals over 40 have a checkup every year. This routine checkup should include a skin examination. During this checkup, a physician will obtain information regarding family history, sun exposure and other risk factors and examine the skin for any abnormalities. The physician may also examine lymph nodes, as enlarged lymph nodes can indicate the presence of melanoma that has spread.
Careful Follow-up: Patients who have been diagnosed with melanoma have a 10-25 times greater risk of developing a second melanoma than the general population. As a result of this increased risk, as well as stage-specific risk of recurrence, patients should be evaluated using stage-appropriate surveillance strategies which will be discussed below. These evaluations should include a history with investigation of specific symptoms and a physical exam that includes a detailed skin and lymph node assessment. Particularly in patients previously diagnosed with early stage melanoma, routine skin assessments are designed to detect and treat a second melanoma in its earliest stages.
Recently, researchers at the John Wayne Cancer Institute conducted a clinical study involving over 3,000 patients who had been diagnosed with early stage melanoma between 1971 and 1999. At the time of treatment of their initial melanoma, these patients were thoroughly educated on performing self skin exams and instructed to seek medical attention if they observed any sign of a suspicious skin change. In addition, patients underwent a complete physical by a surgical oncologist and a complete skin assessment by a dermatologist every 6 months for 5 years following treatment of their initial melanoma. At five years and thereafter following treatment of the initial melanoma, patients underwent yearly physical examinations by a surgical oncologist and were advised to continue biannual examinations by a dermatologist.
Of these patients, 114 developed a second skin melanoma. Records for both melanomas were obtained in 82 of these patients. Of these 82 patients, the thickness of the second melanoma was decreased in approximately 79% of patients. Only 2 patients had a higher stage secondary melanoma than their initial melanoma.
It has been demonstrated that patients who undergo routine skin examination and education in self-exam following the diagnosis of their primary melanoma are likely to detect second melanomas at an earlier stage.