Multifactorial gender disparities in incidence and survival

Although smoking rates have declined in the United States, lung cancer prevalence remains high, and the disease is the number one cause of cancer deaths in men and women worldwide. In 2006 US physicians diagnosed an estimated 174,000 patients with lung cancer, and the disease killed 162,000.

Although lung cancer incidence in men is falling, it is rising sharply in women, making it likely that both sexes will suffer similar rates of the disease in the next decade, says UAB’s Chief of Thoracic Surgery Robert J. Cerfolio, MD, who notes national registry-based studies have shown gender disparities in clinicopathologic characteristics and survival.

“Previous reports have suggested that women with non–small cell lung cancer [NSCLC] fare better than men, but these studies may have been hampered by their retrospective nature or missing or inaccurate data,” he says. “We designed a prospective study to evaluate lung cancer risk factors and trends between genders. To ensure the most accurate data, our patients underwent optimal preoperative staging with CT and PET scans and had all thoracic lymph nodes removed for precise intraoperative pathologic staging.”

Additionally, patients completed a questionnaire about demographic data and social habits. They were asked detailed questions such as type of cigarette smoked, eg, mentholated or nonmentholated. Such data are often lacking in larger national registry studies, and their data may affect outcomes.

Cerfolio and colleagues evaluated 1085 patients (671 men and 414 women) between 1998 and 2005. Investigators balanced the cohort in terms of race, comorbidities, smoking history, pulmonary function, and chemotherapy and resection rates. Women, however, were younger than men, presented at an earlier disease stage, and had a higher incidence of adenocarcinoma.

Despite identical clinical and pathologic staging and treatment strategies for each cancer stage, women with stage I, II, and III NSCLC had increased 5-year survival compared with men. Overall, 60% of women were alive 5 years after surgery compared with 50% of men.

The 5-year postresection survival rates differed by stage and sex: For stage I disease, postsurgical survival was 69% for women and 64% for men; for stage II disease, 60% for women versus 50% for men; and for stage III cancers, 46% for women versus 37% for men (Chest. 2006;130:1796-1802). “At all stages, women had better survival rates than men, even when adjusted for other factors, including age and histology,” Cerfolio says. “Women also were more likely to respond to neoadjuvant chemotherapy.”

Study coauthor Ayesha S. Bryant, MSPH, MD, says possible explanations for these disparities include gender-related biologic, hormonal, molecular, and infectious factors that may predispose women to cancer and alter their response to treatment. “For example, studies have linked human papillomavirus [HPV] with NSCLC, thus raising the question of whether the HPV vaccine will affect NSCLC incidence in women,” she says. “The gender disparity also may be affected by access to care as women tend to see their physicians more often than men, allowing greater opportunities for diagnosis.”

“More research could better elucidate NSCLC pathophysiology, helping scientists develop therapies that improve the dismal 13% overall 5-year survival rate,” Cerfolio says.

For more information
Dr. Robert Cerfolio
Dr. Ayesha Bryant
1.800.UAB.MIST
mist@uabmc.edu