Lung cancer, the third most common cancer in women
Although it was considered a "man's disease", the increase in the number of new cases among women has caused this perception to be lost.
Lung cancer is the leading cause of cancer death worldwide and in Spain, accounting for 18% of all cancer deaths. In 2020 there were 283.000 new cases of lung cancer and 113.000 deaths for this disease in Spain.
Although lung cancer was traditionally considered a "man's disease", the worrying increase in the number of new cases among women has caused this idea to be gradually lost. Currently, lung cancer is the third most common cancer in Spanish women (after breast and colon-rectal cancer) and the second cause of death from cancer among them, after breast cancer.
Temporal trends in lung cancer mortality in Spain have been declining among men since the 90s, while in women have continued to increase progressively. These differences between the sexes have been attributed mainly to the later incorporation of women to smoking, which continues to be the main cause of lung cancer, being responsible for more than 80% of lung cancers.
It is currently estimated that in Spain 23% of men and 16% of women are habitual smokers, having observed a progressive increase in smoking in women since the 70s, something that is clearly having an impact on the current incidence and mortality from lung cancer in women. Compared with men who develop lung cancer, women with lung cancer are younger, start smoking later in life and smoke less heavily than men, something that has been suggested by a increased susceptibility in women to the carcinogenic effects of tobacco. On the other hand, various studies indicate that, once a woman acquires the smoking habit, the possibility that she will give it up is lower than in men. The main histological type of lung cancer in women is adenocarcinoma, regardless of smoking habits.
However, the incorporation of women to the smoking habit is not the only cause of this growing "epidemic" of lung cancer in women, since 20% of lung cancers occur in non-smokers. It appears that non-smoking women are more likely to develop lung cancer than non-smoking men, a fact that suggests biological differences between the sexes. Various mechanisms are being explored that could explain the greater vulnerability of women in the face of this disease, such as a greater susceptibility to the carcinogenic effects of tobacco, the role of certain hormones such as estrogens, the ability to repair damaged DNA, and genetic mutations and infections, among others.
Survival is another epidemiological indicator that informs us of the impact of the disease and that reflects the natural history of this cancer and the effectiveness of treatments. In this case, lung cancer survival at 5 years is very low, although slightly better among women (17%) than among men (12%). In other words, lung cancer is a very aggressive tumor, with only about two in ten women and one in ten men still alive 5 years after diagnosis. This is because, in more than half of the cases, the disease is detected in advanced stages, when treatments are less effective.
Why is it so difficult to diagnose lung cancer in its early stages? Many times lung cancer does not produce symptoms in the early stages and when they do appear, they are often confused with the symptoms of other respiratory diseases. This could delay the correct diagnosis, especially among young women who do not present the typical profile of the disease. One of the warning signs associated with lung cancer is a cough or hoarseness that does not go away or worsens over time. However, the results of a recent population survey that we carried out in collaboration with the Spanish Association Against Cancer (AECC) showed that 24% of the Spanish population would wait more than three weeks to contact their doctor for this symptom or would not contact absolutely.
Another key strategy for early diagnosis of lung cancer could be through a population screening, something that the Ministry of Health is evaluating to implement in people at risk. Screening would involve performing a detection test, in this case an imaging test, low-dose computed tomography (LDCT), in high-risk patients, classified according to age and duration and intensity of smoking. Numerous scientific studies support the implementation of this detection program, which promises to detect cases at earlier stages and reduce mortality. To what extent screening would benefit women compared to men remains to be seen, as as is often the case in many scientific studies, women have been far less represented in clinical trials that established the benefits of screening.
But it seems clear that the best way to prevent lung cancer, for both women and men, is not to smoke and to avoid smoke from people who smoke. Tobacco smoke also causes cancer in nonsmokers who inhale tobacco smoke from smokers and in children of parents who smoke. Ten years after quitting, even if you have smoked for many years, your chances of developing lung cancer decrease significantly.
Campaigns specifically targeting women are needed so that, on the one hand, they encourage her to give up the tobacco habit and, on the other, know the symptoms of lung cancer to be able to detect it in time.
Dr. Maria José Sánchez Pérez is a professor at the Andalusian School of Public Health and Scientific Director of the Biosanitary Research Institute of Granada (ibs.GRANADA)