Lung Cancer

Sex and Gender-based Analysis of this topic

Definition

Lung cancer is the leading cause of cancer death in both Canadian women and men [1]. Tobacco smoke is the most common risk factor of lung cancer, followed by indoor exposure to radon gas especially in radon rich areas and second-hand smoke exposure [2]. The combined number of lung cancer cases for both men and women (23,400) is less than the number of prostate diagnoses (25,500) in men, but more than the number of breast cancer diagnoses (22,700) in women [1]. More deaths are due to lung cancer than from cancers of prostate, colon and breast combined. For men over the age of 69, lung cancer incidence and mortality rates have levelled off due to overall decreases in tobacco use over the last thirty years. However, women’s lung cancer incidence rates have only begun to level off recently, while lung cancer mortality in women continues to increase. This parallels historic trends in women's smoking, which peaked later than for men.

There are two main types of lung cancer based on the appearance of the cells: non-small-cell lung cancer (NSCLC) is an umbrella term that includes squamous cell carcinoma, adenocarcinoma and large cell carcinoma; and small-cell carcinoma (SCLC, also known as oat cell carcinoma). SCLC grows quickly and often spreads to other parts of the body before diagnosis [3] while NSCLC grows and spreads more slowly. More than half of all newly diagnosed lung cancer cases occur in individuals over the age of 50 [1]. Survival rates are highest in cases with localized (no spread) NSCLC tumors, which are rare [2].

 
 
Sex Issues

The likelihood of dying from lung cancer is 1 in 13 for men and 1 in 18 for women while the five-year relative survival ratio (RSR), a measure of patient survival, is 13% for men and 17% for women [1]. The differences may be accounted for by biological differences between the sexes. For example, women have smaller airways than men and may have a lower tolerance to cigarette smoke. In addition, the way women metabolize cigarette smoke may differ due to hormone differences [4].

Women may have some protective factors as evidenced by women being more likely to be living 10 years after lung cancer surgery compared to men [5]. However, women (even women who are non-smokers) may be at increased risk for developing lung cancer due to a gastrin-releasing peptide processor gene that is located on the X chromosome, which plays a role in lung cancer [6].  Women who quit smoking can reduce their overall risk for lung cancer; but cessation is not a guarantee. Five years smoke-free will halve the risk of any tobacco-related cancer, and 10-15 years of being smoke-free reduces the risk to almost that of a woman who never smoked.

 
 
Gender Issues

Women’s higher rates of lung cancer mortality over the age of 50 may be due to societal pressures to smoke in the post-World War era [2]. Early age of smoking initiation has been identified as a risk factor for lung cancer, even more so than duration or amount smoked [2], which is problematic for women given that many women start smoking at an earlier age [7]. Additionally, deeper inhalation and more frequent puffs have been identified as a risk behaviour for women but not in men [8], however, duration of smoking may be the most important risk determinant.

Environmental exposure to certain pollutants, such as asbestos and arsenic, has also been linked to lung cancer. This may put men at increased risk with regards to certain professions (e.g., construction workers or miners). However, women are also at risk for environmental exposure to environmental or second-hand smoke, particularly in service-industry jobs that are predominantly held by women [9].

 
 
Diversity

Lung cancer rates vary across Canada. Quebec has the highest rates of lung cancer incidence, while British Columbia has the lowest incident rates [1]. Females in Quebec have the highest lung cancer mortality, while females in Alberta and Saskatchewan have the lower lung cancer mortality.

In Canada, the highest RSR for men and women is in Manitoba (19%), while the lowest RSR is in Prince Edward Island (11%). Low-income women who have limited access to fresh fruits and vegetables may be at further risk for developing lung cancer [10] as a diet high in vegetables and fruit may offer a protective effect in terms of developing lung cancer.

 
 
Critique

Improving biomedical, health services, social, cultural, and policy research is needed in order to address the gaps in the literature on women and tobacco [7]. Minimal sex-disaggregated data exist for certain groups, such as Aboriginal people, adolescents under 15 years, and Francophones. Researchers have suggested a need for further quantitative studies exploring the relationships between age, smoking initiation, smoking before pregnancy, lifetime exposure to tobacco smoke, and the duration of pack-years smoking [11].

 
 
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