Aetiological factors in lung cancers in Chinese female patients who are non-smokers

Abstract

The lung cancer incidence in Chinese women is among the highest in the world, but most of the patients are life-long non-smokers, and adenocarcinoma is the predominant cell types. These findings have prompted studies to find possible aetiological factors for lung cancer in these non-smoking female patients.

Environmental inhaled agents: Indoor coal burning for heating and cooking in unvented homes has been found to give a risk ratio of 2.2 to 5.9 in Xuan Wei county and Guangzhou. Cooking oil vapours - Both epidemiologic and laboratory studies, mainly from Shanghai, have implicated its role. A recent study showed that high temperature wok cooking with unrefined Chinese rapeseed could increase lung cancer risk. Environmental tobacco smoke - studies in China and Hong Kong have shown inconsistent findings with risk ratio ranging from 0.79 to 2.86. No association has been found with exposure to kerosene stove cooking, incense burning and indoor radon. In fact, a Taiwanese study has found that incense burning was associated with decreased risk for lung cancer. Diet: A Hong Kong study has shown a possible protective effect against lung cancer associated with consumption of fruits, leafy green vegetables and food sources rich in vitamin A, whereas cured meat, salted fish and other preserved food were associated with increased risk. Tuberculous scar: In Hong Kong, both TB and lung cancer are common, but a surgical-pathological study did not find a causal relationship between TB scar and lung cancer. A retrospective cohort study in Shanghai however found that in women with TB, the risk for lung cancer, adjusted for smoking, was 2.79. Genetic factors: The observed worldwide high incidence of lung cancer in non-smoking Chinese women raised the possibility of genetically determined susceptibility factors. But studies of HLA A and B antigens, K-ras oncogenes, p53 and other molecular analysis have so far not shown any positive associations. Hormonal factors (Menstruation): Studies from Shanghai have shown (i) increased risk for adenocarcinoma of lung m women with shorter menstrual cycles and (ii) increased risk for squamous cell lung cancer in women with a higher total number of menstrual cycles. Further studies on environmental, genetic and hormonal factors should continue.