Lung cancer risk among nonsmoking Chinese women pinned to family history

People who have never smoked in their lives still run the risk of developing lung cancer, and among Chinese women in Singapore, this risk is attributed to a history of lung cancer in the immediate family.

In a local study that involved 1,159 women of Chinese ethnicity aged 67 years on average, having a first-degree relative with lung cancer was found to be an important risk factor for lung cancer overall (adjusted odds ratio [aOR], 2.08, 95 percent confidence interval [CI], 1.25–3.47), even more so among women who never did smoke (aOR, 2.78, 95 percent CI, 1.57–4.90). [Sci Rep 2021;11:21862]

Further stratification by fruit consumption (cutoff, 7.36 servings/week) also showed a significant association between family history of lung cancer and higher risk of lung cancer among never-smokers who had low fruit intake (≤ vs >7.36 servings/week: aOR 3.09, 95 percent CI, 1.37–7.01).

While these results are consistent with previous studies, the investigators stressed that the relationship between a family history of lung cancer and lung cancer risk among women cannot be immediately ascribed to the heritability of genes that cause susceptibility to the cancer. This is because shared lifestyle habits may play a role as well. [Eur J Cancer 2012;48:1957-1968; Chin J Lung Cancer 2010;13:224-229; Cancer Causes Control 2010;21:1091-1104]

“[Then again], our stratified analysis by smoking status … suggests that familial clustering of lung cancer is possibly not due to shared familial smoking habits among Singaporean women,” the investigators said.

Also, with regard to the fact that dietary factors may potentially alter gene expression via epigenetic mechanisms, the protective effect of fruit consumption appears to be outweighed by having a family history of lung cancer, the investigators pointed out. They noted that even among women consuming high amounts of fruit in the study, the risk of lung cancer was still elevated. [Nat Commun 2018;9:3375]

The analysis included 374 Chinese women with lung cancer and 785 noncancer controls. Smoking was accordingly more prevalent among lung cancer patients (p<0.001). Compared with controls, patients were more likely to have a history of respiratory disease (16.3 percent vs 11.7 percent; p=0.021), family history of cancer (9.9 percent vs 5.4 percent; p=0.009), and lower body mass index (median, 21.6 vs 23.3 kg/m²; p<0.001). The latter also consumed less meat (median, 11.2 vs 13.8 servings/week; p<0.001), fruits (median, 4.9 vs 7.4 servings/week; p<0.001), and vegetables (median, 14.4 vs 17.3 servings/week; p<0.0047).

“To our best knowledge, this is the first study in a Southeast Asian population to investigate the association between family history and lung cancer risk. Even though there has been literature published on risk factors for lung cancer in Singaporean women, there is still much to be studied about this population,” according to the investigators. [Nutr Cancer 2011;63:850-859; Environ Health Perspect 2010;118:1257-1260]

“Furthermore, this study population was unique in that it had a high proportion of never-smokers among lung cancer cases (67.1 percent). This allowed us to conduct analysis restricted to never-smokers, even when stratified by other risk factors, while retaining appreciable statistical power,” they added.

The investigators called for additional studies evaluating the role of a family history of cancer in other ethnicities and lung cancer subtypes.