“In this first Australian prospective study of lung cancer survival comparing men and women, we found that men had a 43% greater risk of dying from their lung cancer than women,” comments lead author Xue Qin Yu, PhD, the Daffodil Centre, the University of Sydney, and colleagues.
“[However], when all prognostic factors were considered together, most of the survival differential disappeared,” they add.
“These results suggest that sex differences in lung cancer survival can be largely explained by known prognostic factors,” Dr. Yu and colleagues emphasize.
The study was published in the May issue of the Journal of Thoracic Oncology.
The ‘45 and up’ study
The findings come from the Sax Institute’s 45 and Up Study, an ongoing trial involving over 267,000 participants aged 45 years and older living in New South Wales, Australia. Patients were recruited to the study between 2006 and 2009. At the time of recruitment, patients were cancer free.
A total of 1,130 participants were diagnosed with having lung cancer during follow-up – 488 women and 642 men. Compared with men, women were, on average, younger at the time of diagnosis, had fewer comorbidities, and were more likely to be never-smokers or to have been exposed to passive smoke.
Women were also more likely to be diagnosed with adenocarcinoma than men and to receive surgery within 6 months of their diagnosis.
“Lung cancer survival was significantly higher for women,” the authors report, at a median of 1.28 years versus 0.77 years for men (P < .0001).
Within each subgroup of major prognostic factors – histologic subtype, cancer stage, cancer treatment, and smoking status – women again survived significantly longer than men.
Interestingly, the authors note that “women with adenocarcinoma had significantly better survival than men with adenocarcinoma independent of smoking status,” (P = .0009). This suggests that sex differences in tumor biology may play a role in explaining the sex survival differential between men and women, they commented. That said, never-smokers had a 16% lower risk for lung cancer death than ever-smokers after adjusting for age, the authors point out.
The authors also note that approximately half of the disparity in survival between the sexes could be explained by differences in the receipt of anticancer therapy within 6 months of the diagnosis. “This could partly be due to a lower proportion of men having surgery within 6 months than women,” investigators speculate, at 17% versus 25%, respectively.
Men were also older than women at the time of diagnosis, were less likely to be never-smokers, and had more comorbidities, all of which might also have prevented them from having surgery. Women with lung cancer may also respond better to chemotherapy than men, although the sex disparity in survival persisted even among patients who did not receive any treatment for their cancer within 6 months of their diagnosis, investigators point out.
Furthermore, “smoking history at baseline was identified as a significant contributing factor to the sex survival disparity, explaining approximately 28% of the overall disparity,” Dr. Yu and colleagues observe.
Only 8% of men diagnosed with lung cancer were never-smokers, compared with 23% of women. The authors note that never-smokers are more likely to receive aggressive or complete treatment and respond well to treatment.
Similarly, tumor-related factors together explained about one-quarter of the overall sex disparity in survival.