Introduction

Risk Factors for lung cancer include increased exposure to radon gas, personal traits such as a family history of lung cancer, and smoking status and environmental tobacco smoke (ETS) exposure. The NRC, Biological Effects of Ionizing Radiations (BEIR) VI report, Health Effects of Exposure to Radon concludes that indoor radon is “the second leading cause of lung cancer after cigarette smoking”. The EPA estimates that among nonsmokers, increased radon exposure is the leading cause of lung cancer. (NRC 1999; EPA 2003). This is important information when deciding on appropriate assessment strategies, even if the patient is not exhibiting symptoms.

In cases where increased exposure to radon is suspected, the medical evaluation might include

• An exposure history
• A medical history with review of organ systems,
• A physical examination, and
• Additional laboratory testing as clinically indicated.

Patients with potential exposure to increased radon levels should undergo a thorough medical evaluation.

Currently no effective, community-wide screening methods are available for medical prevention or early diagnosis and treatment of lung cancer—radon-induced or otherwise. Neither the American Cancer Society (ACS) nor any other medical/scientific organization recommends for or against screening for the detection of early lung cancer in asymptomatic persons (AAFP 2010; CTFPHC 2003; Smith 2009; USPSTF 2004).

Exposure History

A detailed exposure history is an important step in evaluating a patient who may be at risk for health outcomes related to increased radon exposure. In general, radon levels typically encountered in a community’s outdoor ambient air have not resulted in short- or long-term adverse health effects. That said, increased exposure doses may be significant for some and could result in more serious health outcomes requiring further evaluation and treatment.

An exposure history as part of the patient history will aid in assessing potential exposure to increased levels of radon. The exposure history may include

• A work history of any current and past occupations is relevant in evaluating this and other exposures, especially occupations in which the patient may have been exposed directly or indirectly to radon.
• Age of home (to determine how tightly the building may be sealed).
• Family history of lung cancer.
• Number and type of gas appliances used in the home. Are the appliances vented to the outside? Do they have double wall pipe? (This will identify improperly vented gas-fed stoves and fireplaces, gas dryers, and water heaters).
• Presence and numbers of smokers in the home.
• Testing results from radon measurements in their home.
• Time spent in the basement or lower level of the structure (depending on the type of home).
• Type of home foundation (e.g., built on a slab, with a crawl space, finished or unfinished basement).
• Types of ventilation (opening windows and frequency) systems in the home.

The ATSDR Case Studies in Environmental Medicine: Taking an Exposure History Course provides more information and a sample form to use when taking an exposure history (ATSDR 2009, http://www.atsdr.cdc.gov/csem/csem.asp?csem=17&po=0).

Medical History

Knowing the complete medical history of a patient who has been exposed to increased radon levels can help in making an accurate diagnosis. To ask about lung function is especially important—the lung is the target organ for inhaled radon.

No signs and symptoms are specific to increased levels of radon gas exposure.

Typically, radon-associated lung cancer has a long latency period; many patients exposed to increased levels of radon may be asymptomatic for years. Clinical manifestation of target organ toxicity is based on

• Route of exposure
• Dose
• Genetic factors
• Frequency, duration, and intensity of exposure, and
• Time elapsed since exposure.

Physical Exam

Increased radon exposure can result in lung cancer. But the exposure has no acute or subacute health effects, no irritating effects, and no warning signs at levels normally encountered in the environment.

A physical examination of patients with potential exposure to increased radon levels needs to focus on signs and symptoms of the respiratory system. Although physical examination may not provide radon-specific information, to determine whether radon exposure has or has not occurred is important. The physical examination might be indeterminate for assessing lung cancer specific to radon exposure. Still, to proceed is clinically reasonable, given that radon is a significant environmental cause of lung cancer deaths and may cause lung disease.

Lung cancer’s clinical presentation may vary; some patients may be asymptomatic. In fact, about 25% of people with lung cancer do not have advanced cancer symptoms from when their lung cancer is detected (Humphrey 2004). When present, lung cancer symptoms may include

• Shortness of breath,
• Persistent cough,
• Wheezing,
• Hemoptysis, and
• Chest pain.

Other lung cancer-related changes that can sometimes occur may include repeated bouts of pneumonia, changes in the shape of the fingertips, and swollen or enlarged lymph node (glands) in the upper chest and lower neck (Harrison 2008).

Clinical presentation and clinical judgment will dictate the next steps in assessment, using the data retrieved from the history and the physical exam. This may include testing, referral to a specialist, or both.

Testing

To determine the most beneficial method(s) to test for lung cancer in an asymptomatic patient potentially exposed to increased radon levels, more studies are needed. Methods may include using either low-dose computerized tomography (LDCT), chest x-ray (CXR), sputum cytology, or a combination of these tests (Smith 2009; USPSTF 2004). Still, whether these tests can help prevent deaths from lung cancer is currently unknown.

For more information about lung cancer diagnosis and treatment, visit the National Cancer Institute’s (NCI) Physician Data Query (PDQ) sites. http://www.cancer.gov/cancertopics/pdq

Community Wide Screening

Screening at the community level for lung cancer in asymptomatic persons involves both benefits and risks.

Screening is best described as tests to assess the likelihood of a disease or condition in an apparently healthy person. The fundamental purpose of screening is to prevent the onset of disease through early diagnosis and treatment.

Currently no effective, community-wide screening methods are available for medical prevention or early diagnosis and treatment of lung cancer—radon-induced or otherwise—in asymptomatic persons. Neither the American Cancer Society (ACS) nor any other medical/scientific organization recommends for or against screening for the detection of early lung cancer in asymptomatic individuals (AAFP 2010; CTFPHC 2003; Smith 2009; USPSTF 2004).

But consider: screening for lung cancer that involves taking a CXR adds to the person’s radiation dose and increases the risk of lung cancer.

The sensitivity of LDCT for detecting lung cancer is four times greater than the sensitivity of CXR. Compared with CXR, however, LDCT is associated with a greater number of false-positive results, more radiation exposure—up to 100 times the radiation dose of a CXR—and increased costs.

Because of the high rate of false-positives, lung cancer screening will subject many patients to invasive diagnostic procedures. Although the morbidity and mortality rates from these procedures in asymptomatic individuals are not available, mortality rates because of complications from surgical interventions in symptomatic patients reportedly range from 1.3 to 11.6%; morbidity rates range from 8.8 to 44%, with higher rates associated with larger resections (USPSTF 2004).

Other potential screening hazards are potential anxiety and concern from false-positive results and misplaced reassurance from false-negative results. These hazards, however, have not been adequately studied.

”The benefit of screening for lung cancer has not been established in any group, including asymptomatic high-risk populations such as older smokers. The balance of harms and benefits becomes increasingly unfavorable for persons at lower risk, such as nonsmokers” (USPSTF 2004).

Progress Check