Can heredity contribute to cancer is a question that medical researchers across the world have been trying to answer for a long time. Genetic science has always been searching for the answer through several bodies of work over the years, though some have by now partially linked it to lung cancer, which is mostly caused by smoking.
A latest study in Taiwan has, however, found clear evidence for a family history of lung cancer. The study — The Taiwan Lung Cancer Screening in Never-Smoker Trial (TALENT), published in The Lancet journal on November 29 — has established that people with a family history of lung cancer have a much higher risk. The higher the number of first-degree relatives affected, the higher the risk of lung cancer, the study shows.
The Lancet report said that the participants in the TALENT study whose mother or sibling had lung cancer were at an increased risk of the disease. This finding has shaken the general belief until now that smoking is the predominant cause of lung cancer. The Taiwanese study was prompted by the particular situation in the country that lung cancer occurs predominantly in never-smokers, of whom nearly 60% have stage IV disease at diagnosis.
What does the study say
The Taiwanese trial, which primarily focussed on screening the other risk factors for lung cancer among never-smokers, was a nationwide, multicentre, prospective cohort study. This eight-year-long study was initiated at 17 tertiary medical centres in Taiwan. It recruited people aged 55-75 with either no history of smoking or who stopped smoking for more than 15 years.
The trial, however, found that most of these people had one of the following risk factors — a family history of lung cancer; passive smoke exposure; a history of pulmonary tuberculosis or chronic obstructive pulmonary disorders (COPD); a cooking index of 110 or higher; or cooking without using ventilation.
According to the Lancet report, between December 1, 2015, and July 31, 2019, 12,011 participants, of which 8868 were females, were enrolled for the TALENT study. Of these, 6009 people had a family history of lung cancer.
Among the total trial volunteers, who were scanned with low-dose computed tomography (LDCT) for lung cancer, 2094 (17·4%) were positive, and a clear case of lung cancer was diagnosed in 318 (2·6%) participants. In participants with a family history of lung cancer, the detection rate of invasive lung cancer increased significantly with age, the report said.
In multivariable analysis, female sex, a family history of lung cancer, and age older than 60 years were associated with an increased risk of lung cancer. However, passive smoke exposure, cumulative exposure to cooking, cooking without ventilation, and a previous history of chronic lung diseases were not associated with lung cancer, even after stratification by family history of lung cancer.
Detection of lung cancer
In the study, lung cancer was diagnosed through invasive procedures, such as image-guided aspiration, biopsy or surgery. The primary outcome was lung cancer detection rate. Univariate and multivariable logistic regression analyses were also used to assess the association between lung cancer incidence and each risk factor.
“In individuals who do not smoke, our findings suggest that a family history of lung cancer among first-degree relatives significantly increases the risk of lung cancer as well as the rate of invasive lung cancer with increasing age,” wrote the researchers in the Lancet report.
Even though the report says that further research on risk factors for lung cancer is needed, particularly for those without a family history of lung cancer, the overall findings certainly reveal the direct genetic linkage of cancer, at least in the case of the targeted disease — lung cancer.
Genetic linkage of lung cancer
While smoking remains the most important cause of lung cancer, some of the earlier studies have also reported similar findings, establishing the genetic causes of lung cancer. According to global patient data, smoking is considered responsible for 80-90% of lung cancer cases and it is estimated that close to 8% of cases are linked to family history and genetic reasons.
While a lung cancer history in the family doesn't need to result in more cases in the same generation or the next, previous studies have suggested that genetics plays a key role in the spread of lung cancer in never-smokers, young people below the age of 50 and the female population.
Certain genetic mutations (changes or alterations in one’s genetic code) found in families increase the risk of lung cancer, though it doesn't mean that all such genetic mutations are inherited from generation to generation.
At the same time, “...one can inherit genetic mutations, or acquire these changes at any time during his/her life due to environmental factors such as smoking or environmental pollution,” says Dr Lynne Edridge, a cancer expert and author, in her recent report in verywell health.
Lung cancer in India
According to a 2022 survey by the Indian Council of Medical Research (ICMR), India had about 70,275 lung cancer cases. Being one of the most prevalent cancers with a high mortality rate, lung cancer accounts for 9.3% of all death cases in the country at present.
While the rising incidence and delayed diagnosis of lung cancer in India are serious concerns, current estimates show that the number of cases is expected to rise sharply to 81,219 cases among males and 30,109 in females in the next two to three years.
Conclusion
More scientific evidence to prove that genetic mutations contribute to lung cancer is quite useful information to the healthcare world. The currently established diagnosis and treatment protocols as well as the disease prevention measures globally as far as lung cancer is concerned are still mostly based on the assumption that it is a smoker’s disease.
Since lung cancer is a significant public health concern in low-and middle-income countries, including India, an informed revision in the approach is imperative.
Hence, it’s time to make necessary changes in the disease prevention standards and to include family-based screening to control the potential spread of lung cancer in the current as well as future generations.
(Edited by : Amrita)
First Published: Dec 1, 2023 8:54 AM IST
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