Epidemiology study of never-smokers with non-small cell lung cancer (NSCLC): High percentages of Asian and Hispanic female never-smokers and the significance of Asian ethnicity
Non-small cell lung cancer (NSCLC) remains the number one cause of cancer death in both men and women in the United States. The greatly increased risk of NSCLC development in tobacco users has been well recognized for several decades. More recently, a sharp rise has been seen in NSCLC among never smokers and this cancer has been found to be biologically different from that of a NSCLC in a current of former smoker. Common features of never-smokers with NSCLC have been identified, including East Asian ethnicity, female sex, adenocarcinoma (specifically bronchoalveolar) pathology, and an increased likelihood of EGFR mutations, which may result in different therapy choices. This study attempted to increase the understanding of the epidemiology (the occurrence and distribution) of NSCLC in never smokers and to look at the affect of ethnicity on prognosis.
Utilizing a southern California database that included smoking status, 2240 never smokers were identified with a NSCLC diagnosis (and compared with 22964 current and former smokers). Never smokers had significantly improved survival when compared with smokers. Never smokers responded better to chemotherapy, with an 8 month median survival in never-smokers versus 6 month median survival in smokers with metastatic disease receiving chemotherapy. Response to radiation therapy also appears to be better.
When the never smokers (NS) were compared to the smokers (SK), the NS group contained more females, their tumors were more likely to be adenocarcinoma and more specifically, bronchoaveolar. When looking at ethnicity, 13% of Caucasian women were NS, 45% of Asian women were NS, and 25% of Hispanic women were NS. Of women born in North America, 11% of women born in Canada and 12% of women born in the United States with NSCLC were never-smokers. Thirty percent of women born in Mexico with NSCLC were never smokers. Of women born in Asian countries with NSCLC, 53% of Philippine women, 64% of Vietnamese women, 17% of Japanese women, and 61% of Chinese women were never-smokers.
Being of Asian ethnicity was a favorable prognostic sign for both NSs and SKs. Other groups have demonstrated improved responses among Asian women to certain therapies. While the information from this study is interesting, actual treatments were not considered and the population was limited to one geographic area. It is unclear what is driving the rise in these ethnic groups. Further studies must look at exposures and genetics as possible causes and evaluate how ethnic factors play into treatment decisions.