A study published Feb. 5 by four researchers, including two from ACS, finds that the emerging pattern of higher lung cancer incidence among young women than young men is widespread across geographic areas and income-levels.
The authors say this pattern "is not fully explained by sex-differences in smoking prevalence, underscoring the need for etiologic studies." They also warn that "our findings forewarn of a higher lung cancer burden in women than men at older ages in the decades to follow. Further work is therefore needed to intensify anti-tobacco measures and identify factors for the higher incidence of lung cancer among young women."
The study was published online in the International Journal of Cancer.
The two ACS researchers contributing to the study are Lindsey Torre, MSPH, and Ahmedin Jemal, DVM, PhD. This new study extends an earlier study led by Dr. Jemal that found that in the U.S. the incidence of lung cancer in young women is higher than that in their male counterparts.
The researchers examined lung cancer incidence rates from 1993 to 2012 in women and men, ages 30 - 64, in 40 countries across five continents. Among men, the age‐specific lung cancer incidence rates generally decreased in all countries, while in women the rates varied across countries with the trends in most countries stable or declining, albeit at a slower pace compared to those in men. As a result, rates in ages 30-49 years became higher in young women than in young men in Canada, Denmark, Germany, New Zealand, the Netherlands, and the United States, reversing the historically lower rates in women than men. This crossover was largely driven by growing adenocarcinoma incidence.
The researchers posit that "it is possible that females may be at an increased risk of lung cancer compared to males.” They cite a pooled analysis of 13 studies that “found that lifelong female nonsmokers of European, African American, and Asian-descent had higher rates of lung cancer compared to their male counterparts." It's possible, they write, that women have a higher susceptibility to lung cancer because of various gene variants. "Research has suggested that women with lung cancer have impaired DNA repair mechanisms compared to men, which makes them especially susceptible to lung cancer," the researchers wrote.
Historically, lung cancer rates have been higher among men because they start smoking in large numbers earlier and smoke at higher rates, the researchers explained. However, there has been a convergence in lung cancer incidence between men and women.
With an estimated 2.1 million cancer cases in 2018, lung cancer is the most common cancer worldwide among men and the second most common cancer among women. By histologic type, it is grouped into four major categories: nonsmall cell carcinoma, adenocarcinomas, squamous cell carcinomas, and large cell carcinomas.
Cigarette smoking is the main risk factor for all lung cancer subtypes, though the risk of lung cancer associated with smoking is greater for small cell and squamous cell lung cancers than the other types. Other known risk factors for lung cancer include exposure to secondhand smoke, mineral and metal dust, asbestos, and radon.
The best way to avert future lung cancer cases and deaths among current smokers is through smoking cessation. The risk of dying of lung cancer can be reduced substantially by quitting at any age.