Introduction and Background
Cancer is not a single disease. There are over 200 types of cancer afflicting individuals of all ages. It is also not necessarily a fatal disease. Depending on the type, some cancers are completely curable in over 95% of the cases, whereas other types of cancers are nearly always fatal.
Overall, cancer is the second leading cause of death in the U.S. for all ages, accounting for about 1 out of four deaths. The percentage of deaths due to cancer tends to peak in the years of early childhood and then again in mid to late adult life. According to the American Cancer Society, in 2014 about 580,000 Americans will die of cancer – more than 1600 people per day.
Despite these statistics, relative survival rates for cancer have been steadily climbing over the past several decades. According to the National Cancer Institute, over 50% of individuals diagnosed with cancer now survive at least 5 years from their diagnosis. Although certainly a serious condition, the diagnosis of cancer is clearly no longer a hopeless one.
What is Cancer?
Cancer is an uncontrolled proliferation of certain abnormal cell types in the body that invade surrounding normal tissue. The cell type and location determine the type of cancer. Cancers can be found in solid tissue or in tissues of the bone marrow, blood or lymph tissues. Cancer does its damage to the host by growing rapidly and robbing normal cells of nutrients. Additionally, cancer can spread to other areas, a process called metastasis. Cancers can cause secondary problems by obstructing organs, eroding tissue, causing swelling or seizures when found in the brain, or preventing the normal development of different types of blood cells.
Common Forms of Cancer
The most common form of cancer in the U.S. for both men and women, is non-melanoma skin cancer, with about 700,000 new cases annually. The majority of these are basal cell carcinomas (80%), while the remainder are predominantly squamous cell carcinomas. Cumulative exposure to ultraviolet sunlight radiation is the principal risk factor associated with this form of cancer. Fortunately, such cancers are amenable to surgical treatment, with relatively high success rates.
Each year about 1.3 million new cases of other cancers (besides non-melanoma skin cancers) are diagnosed in the U.S. The most common of these in men are prostate, lung, colon, bladder, and rectal cancer. For women, the most common new cancers in order of decreasing frequency, are breast, lung, colon, uterine, and ovarian cancers.
If ordered according to the cancers that cause the most deaths, the lists change slightly because some cancers have a greater potential for response to treatment than others. When forms of cancers are viewed in this manner, the top most lethal cancers for men are lung, prostate, and colon, pancreatic and leukemic cancers. For women, the most common causes of cancer deaths are due to lung, breast, colon, pancrease, and ovarian cancers, in that order.
Studies of Cancer in Pilots
Although several long-term studies have reviewed the occurrence of cancers in pilots, there is no broad consensus that has emerged within the aerospace medicine community regarding those forms of cancers that may occur more frequently in aviators. Results have varied depending on the size of the study, the number of years spanned, the comparison groups used, and the type/reliability of data available for use.
In studies that have focused on aviator deaths due to cancer, one review of 1538 U.S. commercial pilots and navigators suggested that deaths due to kidney cancers might be occurring more frequently than in the general population. Another large British study of 6209 pilots did not confirm the finding of increased kidney cancer deaths, but instead found that the occurrence of deaths attributed to melanomas was significant.
Some studies that looked at frequency of occurrence, rather than death reports, have shown higher rates of urologic cancers like prostate (Canadian study), bladder, and testicular (US Air Force study) cancers. Other studies suggest that pilots actually have decreased rates of certain cancers and other diseases. These findings may perhaps be related to their higher socioeconomic status, frequency of medical surveillance, availability of early medical care, and pre-selection for health. As more data accumulates with time, more reliable conclusions will no doubt become available, and allow for more definitive assessments of cancer risk in commercial pilots.
An excellent review article and synopsis of all scientific studies of cancer in aircrew members to date (meta-analysis) can be found in the journal Aviation, Space and Environmental Medicine, 2000; 71:216-24 “Cancer Incidence and Mortality Among Flight Personnel: A Meta-Analysis” Ballard et al. It concludes that there were slight increased incidence of cancers of the brain and melanoma in male pilots, who also had an increased mortality risk from prostate and brain cancer. The risk of other types of cancer was lower in pilots. Female flight attendants had higher risks of melanoma and breast cancer. The cause for these findings is not clear since it is difficult to separate occupational exposures from routine exposures such as potential for more sun with increased access to travel and potentially increased leisure time.
Stages of Cancer
“Staging” of cancer is a means to help categorize the severity of the disease, establish a prognosis for the individual, and determine a recommended treatment for the condition based on the location and severity of the disease.
A current standard format for staging includes the TMN classification. “T” refers to the size or location of the tumor at its original (or “primary”) site, and whether it has extended to local tissue. “N” refers to the involvement of any lymph nodes. “M” refers to the presence of tumor cells in more distant metastatic sites.
Alternatively, a four-staged, Roman numeral classification is often used. The stages in this system reflect the extensiveness of the cancer, with Stage I being the least extensive and Stage IV being the most extensive. Colon cancer uses a “Duke’s” classification with the earliest stage term “Duke’s A” and the most advanced being a “Duke’s D”. Using these forms of staging does not preclude also categorizing cancer in the TMN classification.
Additionally, cancers can be categorized as to how closely they resemble the original tissue from the primary site. “Well differentiated” cancers resemble the original tissue fairly closely and are considered less severe. “Moderately differentiated” tissues are intermediate in severity and “poorly differentiated” cancers indicate a more serious and aggressive disease. Prostate cancer uses a “Gleason” scale to characterize the differentiation of the cells with higher numbers indicating more poorly differentiated cancers.
Screening for Cancer
Some types of cancer have well-developed screening tests, which attempt to detect disease before it is fully established or at an early enough stage where a cure is likely. Examples include the Papanicolaou smear (PAP) for cervical cancer. Tests such as the prostate specific antigen (PSA) for prostate cancer, a mammogram for breast cancer, or colonoscopies and stool sampling for colon cancers are examples of screening to detect early disease at a hopefully curable stage.
Other types of cancers do not have effective screening tests but do have chemical indicators possibly indicative of the presence of a tumor. One such example is the carcinoembryonic antigen (CEA) level for colon cancer. Many other proxies for cancer detection exist. Lung cancer is the leading cause of cancer deaths in both men and women. Unfortunately, there is no effective screening test available to detect early stages of lung cancer. By the time lung cancer is visible on a chest x-ray, the chances for curing the disease are minimal. Likewise, there is no effective serum tumor marker for lung cancer. New treatment protocols and clinical studies at research institutions may offer improved survival and quality of life in some cases of cancer discovered in later stages.
Other than PAP smears and mammography, most screening tests for cancer do not have broad acceptance or scientific evidence to support their routine use in all populations. Colon cancer screening is slowly gaining acceptance, particularly with a variety of testing methods available.
Positive screening tests generally lead to definitive follow-up evaluations, some of which can involve relatively invasive procedures. This can result in a risk of complications and increased cost for an individual who does not have the disease, but instead simply had an initial test that was a false positive.
Causes of Cancer
Many different factors are considered to place individuals at increased risk for cancer, and each specific type of cancer has its own unique set of risk factors. The strongest associations between risk factors and cancers appear to occur with smoking, radiation exposures, and other lifestyle factors such as diet, alcohol use, and others. A strong family history of a particular type of cancer may also lead an individual to seek early screening for this type of disease.
The use of tobacco, in particular, is felt to be responsible for the development of more cancers than all other causes combined. Those people who knowingly choose to use tobacco products are placing themselves and those around them at increased risk for a significant number of cancers. Exposure to radiation in the form of occupational hazards, natural hazards ( radon and cosmic radiation) and man-made exposures (primarily medical diagnostic tests and treatments), can also pose significant hazards. Recent public education about the hazards of radon in homes causing lung cancer and the role of ultraviolet light in causing skin cancer may reduce the upward trends in these specific diseases. The National Cancer Institute is constantly researching for conducting research to determine avoidable causes of cancer in the general population.
From an aeromedical perspective, the windscreens and metallic skin of aircraft shield flight crews from ultraviolet radiation. Studies are underway to determine if aircrew are exposed to significantly elevated levels of cosmic radiation, and if so, whether aviators are at a resulting increased risk for any form of cancer.
Diagnosis of Cancer
The diagnosis of cancer is usually made by obtaining a piece of tissue to be studied under a microscope. A physician with specialized training in pathology determines whether the tissue is normal or has changes indicative of cancer. This piece of tissue is called a biopsy specimen may be obtained through the skin using a hollow-core needle, by direct surgical excision, or with the aid of various forms of fiberoptic scopes and biopsy forceps.
Possible indications of cancer may also be detected with laboratory studies, testing for tumor markers in the blood, or revealing abnormalities in the function of organs, which may be the site of metastases, such as the liver. Nuclear medicine scans using radioisotopes can also reveal primary and metastatic cancers. Scanning techniques using MRI or CT technology and ultrasound may also reveal the presence of tumors.
Treatments for Cancer
There are a number of possible treatments for cancer. Each type of cancer has its own specific set of medically accepted treatments. Additionally, experimental treatments for cancer are continually being developed. Western medical treatments for cancer include surgical excision or debulking, radiation therapy, chemotherapy, immunotherapy, thermal therapy, hormonal therapy, and the newly evolving gene therapy. Complimentary and alternative medicine practitioners have a host of alternate recommendations for cancer. All medical models encourage optimum nutrition and emotional well being. Additionally, since cancer survivors are susceptible to recurrence of the disease, continued close medical follow-up is essential. Finally, some individuals with cancer elect not to undergo treatment at all, for individual reasons.
Surgical treatments of cancer are generally designed to remove all of the primary cancer. If a particular type of cancer is slow growing and confined to a specific area, surgical removal of the primary cancer may represent a cure. Common examples include early forms of prostate, colon, thyroid, cervical and endometrial cancers. Surgery might also be used to remove metastatic lesions in attempt to slow the progress of the disease, or alleviate symptoms caused by their particular location. For example, surgical excision is used to debulk or reduce the size of the primary tumor or a metastasis that may be affecting other organs, such as an abdominal cancer that is blocking the small intestine.
- Radiation Therapy
Radiation therapy uses high dose, focused radiation beams to kill rapidly growing tumor cells. “Local radiation” uses x-ray beams from two different sources to focus on tumor cells in a circumscribed area.
“Whole body radiation” is often used in certain types of cancer of the blood-forming organs, such as leukemias. This type of treatment may require a subsequent bone marrow transplant procedure to restore the individual’s capacity to produce blood cells.
Another form of radiation treatment, called brachytherapy, makes use of implanted radioactive “seeds” within cancerous tissue to kill the tissue locally. Prostate cancer is an example of where such implants are commonly used.
Chemotherapy employs a variety of different pharmaceuticals and chemicals that can adversely affect normal cells, while targeted cancer cells are being destroyed. For this reason, people often get very sick when undergoing treatment with chemotherapy. Because cancer cells are growing more rapidly than normal cells, the cancer cells presumably take up the chemotherapeutic agents faster than surrounding cells and will be killed sooner.
Unfortunately, to ensure adequate kill rates for cancerous cells, normal cells may also be affected, and as a result, normal body functions can be interrupted. For example, the rapidly reproducing cells such as those of the hair and lining of the gastrointestinal tract are frequently injured causing the symptoms of nausea, vomiting, diarrhea, and hair loss.
A newly evolving field of cancer treatment involves injecting the individual with proteins and other compounds that bind specifically to tumor cells and kill the cells through a variety of mechanisms. An example of this technology has been applied to the treatment of malignant melanomas. Antibodies against the tumor cells are genetically spliced into non-pathologic microorganisms that are injected in the body, where they produce the antibodies that seek out and kill malignant cells.
- Thermal Therapy
Another new technique for treating cancer is the use of heat or cold focused on the tumor to kill the malignant cells. Temperature changes may be induced by physical, chemical or microwave energies.
- Hormonal Therapy
Hormonal therapy is frequently used when tumor cells are sensitive to levels of hormones in the body. By depriving the tumor cells of the hormone, the growth of the tumor is slowed, arrested or reversed. Examples include the use of tamoxifen for breast cancer and the use of Lupron for prostate cancer.
- Gene Therapy
The newest area of research and cancer treatment involves gene therapy. In this technique, genes specific for cancer are substituted within the tumor chromosome with more benign genes, using a technique similar to gene splicing.
Finally, some individuals elect to not undergo any treatment for cancer. The reasons for this decision are varied. In some cases, the cancer grows slowly enough that it is not likely to cause significant illness or discomfort before the individual?s expected death from other causes. Examples include chronic lymphocytic leukemia and prostate carcinoma in older individuals. Some individuals have cancer that has progressed far enough at the time of discovery that any intervention is unlikely to significantly alter quality of life or longevity. In such cases, further treatment can inflict more pain and discomfort than symptomatic treatment alone. Pancreatic carcinoma is frequently in this category. The third possible reason for not undergoing treatment for cancer by traditional Western means would include a lack of confidence in conventional cancer treatment versus alternative treatments, or dissatisfaction with the toxicity of traditional treatments.
Determinants of Prognosis
Prognosis for any given type of cancer is dependent on many factors. These factors include the type of cancer, the stage of disease when discovered, the aggressiveness of the individual cancer, cell type, the types of treatment available, co-existing diseases and the general health of the individual. Any individual with cancer should remember that a prognosis is simply medical sciences? best guess based on a large population with similar diseases. Any single individual can behave quite differently than the generally accepted prognosis. Individuals having experiences outside the standard prognoses are often termed as “having beat the odds”, “having experienced a miracle” or “having a surprisingly rapid demise.”
FAA Policy on Cancer
Most cancers are disqualifying conditions according to current FAA policy. Pilots diagnosed with cancer are obligated under FAR Part 61.53 to ground themselves until their case is reviewed by the FAA or their Aviation Medical Examiner (AME). Exceptions to this rule involve certain superficial, non-melanoma skin cancers and very superficial melanoma skin cancers that have been completely excised. In such cases, pilots may return to flight duty and report the condition at the time of their next physical. The FAA allows AMEs to clear airmen with prostate cancer, certain urological cancers, and pedunculated colon polyps with adenocarcinoma without metastasis (policy is evolving and should be discussed with an AMAS physician).
Most other cancers, however, require documentation of successful removal of the tumor, completion of any therapy, and the absence of metastatic disease before the FAA will favorably consider an airman’s application for a medical certificate. In some cases, the pilot may still be undergoing treatment for disease and be certified. A common example is the use of hormonal suppressive therapy in prostate carcinoma.
The current FAA policy for metastatic cancer requiring intravenous chemotherapy is for a one-year observation period to pass following surgical removal of the tumor. The chemotherapy course must be completed before the case will be considered for certification. Distant metastases not involving the central nervous system may require a three year observation period before recertification consideration. Because of the increased risk of brain involvement with metastatic breast cancer, lung cancer, and malignant melanoma, the resulting potential for seizures or cognitive dysfunction with these metastatic cancers require specific protocols for mandatory observation periods following their treatment. If spread to the central nervous system does occur, a five-year observation period is often required before recertification is possible.
In general, pilots with a history of cancer will be granted a Special Issuance medical certificate allowing the pilot to fly for a limited period of time under their medical certificate. Controllers are granted Special Consideration in the same fashion. Instead of the certificate lapsing to a lower class of certificate, the medical will expire for all classes pending resubmission of updated medical information and a current status report from the treating physician regarding the controller or pilot’s continued freedom from cancer. You may also want to read our article regarding Aeromedical Certification for more details on this process.
Numerous world and national scientific health organizations recommend a variety of lifestyle modifications to lower an individual’s risk of cancer. The most widely recommended and accepted measure is avoidance of tobacco products. Some estimates state that the rate of new cancer cases would be cut in half by avoidance of tobacco use. An additional protective measure against some types of skin cancer is provided by the use of sunscreens that block harmful UV rays. Homes that are found to have elevated radon levels should have effective abatement equipment installed to lower the risk of non-tobacco related lung cancer.
One of the simplest interventions involves changing an individual’s diet to one rich in fruits, vegetables, anti-oxidants, and fiber. Decreasing high dietary fats, which have been associated with colon cancer, is an added protective step.
The American Cancer Society has published Guidelines for Nutrition and Physical Activity for the Prevention of Cancer. This document gives excellent advice of proven, postulated, unproven and harmful interventions for many types of cancer. Of note, moderate regular physical activity is beneficial for nearly every type of cancer.
Finally, each individual should discuss cancer-screening techniques with their attending health care provider to determine which tests may be most appropriate for them.
Sources of Information
Many reputable sources of information on cancer prevention, detection, treatment, and recovery are widely available. These include the American Cancer Society (1-800-227-2345) www.cancer.org and the National Cancer Institute of the National Institutes of Health (1-800-4-CANCER) www.cancer.gov .
AMAS Aeromedical Assistance
For a more specific personal explanation to your questions or those concerning aeromedical certification, contact AMAS for a private consultation. For help in reporting treatment for and obtaining clearance from the FAA to fly or control with these conditions, refer to the AMAS Confidential Questionnaire. If you are an AMAS Corporate Member, these services are FREE to you.