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A recent review examines lung cancer risk in women. SDI Productions/Getty Images
  • Researchers recently published a review highlighting possible reasons why rates of lung cancer among women have remained higher in recent decades than those among men.
  • Various factors, including radon exposure, secondhand smoke, and indoor cooking, may explain this trend.
  • The researchers say that further research is necessary to understand the risk factors for lung cancer among women and that organizations should bear these in mind when updating screening guidelines.

A few decades ago, most cases of lung cancer occurred among men who smoked. Nowadays, however, women are more likely to receive a diagnosis of lung cancer than men, even if they do not smoke.

The reasons behind these higher rates of lung cancer among women are unknown. Possible risk factors include exposure to radon, indoor cooking fumes, genetic differences, and secondhand smoke.

Although women tend to have better outcomes from lung cancer than men, the higher rates among women highlight the need for more research into the risk factors.

Recently, researchers from Stanford University, CA, and the University of California San Francisco published an article summarizing potential lung cancer risk factors among women. They also looked at screening and diagnosis patterns and clinical outcomes.

The researchers found several differences between men and women, including the development of lung cancer, its screening process, its outcomes, and the treatment side effects.

They hope that other researchers and clinicians will pay attention to these differences to improve patient care as lung cancer rates among women remain relatively high globally.

“This is an excellent review article describing some of the known sex-based differences in lung cancer epidemiology and treatment tolerability,” Dr. Andrea McKee, spokesperson at the American Lung Association, told Medical News Today.

“The findings are not surprising to me, but I feel they will be surprising to the general public, particularly the increased association between HPV and lung cancer in women.”

The review appears in the European Respiratory Review.

Although there has been an increase in lung cancer among people who have never smoked, the majority of people with lung cancer have a history of tobacco use.

Overall, the rates of lung cancer in the United States have declined from 67 to 43.2 cases per 100,000 over the last 2 decades, but the rate of decline has been slower for women than men. The reasons for this remain unknown, and studies show that women are not more susceptible than men to carcinogens in tobacco smoke.

According to the Environmental Protection Agency (EPA), radon, a radioactive compound present in soil, rock, and water, is the primary cause of lung cancer in nonsmokers and the second most common cause after tobacco use.

An analysis of seven case-control studies found that high radon exposure in residential settings correlates with an increased risk of lung cancer.

Secondhand smoke is the third most common risk factor for developing lung cancer. A meta-analysis of 37 studies found that women who do not smoke are 24% more likely to develop lung cancer if their spouse smokes than if they also do not.

Indoor cooking fumes may also contribute to lung cancer rates among women. A study from Asia found that women who cook with coal are five times more likely to develop lung cancer than those who do not.

Cooking oils also lead to the formation of polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens. Women who cook in areas with poor ventilation may have increased exposure to PAHs.

A study in Taiwan found that among people who do not smoke, women are more likely to have HPV-positive lung cancer than men.

Research has also linked mutations in genes that affect DNA repair and mutations in the TP53 gene to an increased risk of lung cancer in women. The TP53 gene produces a protein that prevents the replication of damaged DNA and cell division.

Estrogen levels might also be a risk factor. One study found that premenopausal women with lung cancer experienced more advanced disease than postmenopausal women. Other research shows that estrogen receptors are overexpressed in many lung cancers.

Current guidelines worldwide for screening lung cancer require a significant smoking history. They thus exclude growing lung cancer cases among people who do not smoke.

However, up to 80.6% of women who receive a lung cancer diagnosis do not meet the screening criteria that the U.S. Preventive Services Task Force (USPSTF) outlined in 2013.

The USPSTF did update its guidelines in 2021 to reduce the lower limit of screening age from 55 to 50 years and the minimum smoking history from 30 to 20 pack-years. By expanding the screening criteria, more women and racial minorities will be eligible for screening via low density computed tomography (LDCT). However, the exclusion of a rising proportion of the population will continue.

The researchers behind the current study note, though, that LDCT screening should only take place when necessary due to the possible side effects of radiation exposure. An older study from 2004 concluded that carrying out annual screening for half of all those in the U.S. population who are aged 50–75 years and smoke or have smoked would lead to about 36,000 cases of radiation-associated lung cancer.

The researchers conclude that screening guidelines should be expanded to include risk factors beyond tobacco use and that future clinical trials should investigate sex-based differences in lung cancer.

When we asked how this review could inform future research and public health, Dr. McKee told MNT:

“The authors indicate 50–80% of women diagnosed with lung cancer are not eligible for CT lung screening. [A recent publication] demonstrated 56% of lung cancers in women in [the] Chicago Race Eligibility for Screening Cohort Study (883 total patients in the study) were eligible for screening under the new 2021 USPSTF guidelines, which, for the most part, have now been adopted by the Centers for Medicare & Medicaid Services (CMS).”

“This is an improvement over the 2013 guidelines, but there is clearly room for improvement of future public health policies to expand screening eligibility guidelines for the benefit of women,” she concluded.