Clinical and Health Affairs
Lung Cancer in Women—An Unrecognized Epidemic
By Mary J. Boylan, M.D.
ABSTRACT
Lung cancer claims the lives of more women in the United States than breast cancer. The overall 5-year survival rate for lung cancer—15%—has not changed much in the past 50 years. By contrast, the 5-year survival rate for breast cancer in women is 86%. In Minnesota, the number of lung cancer deaths among women started exceeding deaths from breast cancer in 1992. This article looks at the explanations behind the phenomenon and ways to reduce deaths from lung cancer among women.
More American women now die of lung cancer than breast cancer.1 Although the incidence of breast cancer is higher than that of lung cancer, lung cancer claims more women’s lives every year. In addition, while the lung cancer incidence and mortality rates for men have been decreasing over the past few decades, the rates for women have been trending upward.1 Lung cancer is clearly an equal-opportunity malignancy and should be considered a priority in terms of women’s health.
Lung cancer mortality has reached epidemic proportions both in the United States and around the globe, and cigarette smoking is largely responsible for this epidemic. The World Health Organization has identified lung cancer as a major health issue. There were more than 1 million deaths from the disease worldwide in 2000, more than half of which (53%) occurred in developed countries. Women accounted for more than a quarter of those deaths.2
For American women, the statistics are particularly alarming. Since 1930, there has been a 600-fold increase in the death rate from lung cancer.1 In 1950, the incidence of lung cancer was 5 times greater in men than that in women. By 1980, it was only 2.6 times greater in men.3 By 2004, 80,600 of the estimated 173,770 new cases of lung cancer in the United States were diagnosed in women, and nearly half (46%) of all lung cancer deaths occurred in women.4
Although survival rates for many forms of cancer have improved during the last several decades, the rate for lung cancer has remained low. Today, the overall 5-year survival rate for lung cancer in both men and women is 15% in the United States, which is a slight improvement from the mid 1970s, when the rate was 12%. There is a magnitude of difference in survival between lung and breast cancer. By contrast, the overall 5-year survival rate for breast cancer in women is 86%, which is significantly improved from the mid 1970s, when the rate was 75%. When comparing early-stage cancers (ie, cancer without regional or distant metastasis), the disparity between survival rates is even greater, with a 97% 5-year rate for breast cancer and a dismal 49% 5-year rate for lung cancer.5 Breast cancer, which is the most commonly occurring malignancy in women, accounts for 32% of all cancers; lung cancer accounts for 12%. However, lung cancer accounts for 25% of all cancer deaths in women, which is more than the combined number of deaths from breast (15% of total cancer deaths), ovarian (5%), and uterine (3%) cancers.6
Minnesota Data
In 1992, lung cancer became the No. 1 cause of cancer death among Minnesota women, surpassing breast cancer and mirroring national cancer mortality rates, which saw the number of deaths from lung cancer surpass the number of deaths from breast cancer in 1987 (Figure).1 The death rate per 100,000 population for lung cancer in Minnesota women is 36; the rate for breast cancer among Minnesota women is 26.7 Although women in Minnesota enjoy some of the highest health status rankings in the country, the trends in lung cancer mortality have been ominous. From 1988 to 2001, the number of women who died from lung cancer in the state increased by 33% (from 618 to 996), while the number of deaths from breast cancer decreased by 22% (from 765 to 685).8 During that same time frame, lung cancer mortality for Minnesota men decreased by 9%.9
Some subpopulations of women are at even greater risk of developing lung cancer than others. These groups also have higher smoking rates. In Minnesota, the lung cancer mortality rate for African American women is 40% higher than that of white women. American Indian women bear the greatest burden, with a lung cancer mortality rate twice that of white women in the state.8
Women’s Risks
Although lung cancer trends in part can be explained by differing smoking behaviors of women and men during the last several decades, there is growing suspicion that women may have a different risk propensity because of their sex. A study of 1,889 patients with cancer concluded that dose for dose women were more susceptible to the carcinogens in tobacco than men.10 Other large studies of men and women with lung cancer found that the women tended to be younger, consumed fewer cigarettes on a daily basis, and had smoked for a shorter period of time than the men.11-13 They also found an over-representation of adenocarcinoma in women.
Adenocarcinoma is one of 4 major lung cancer cell types: squamous cell, large cell, and small cell undifferentiated being the others. Squamous cell was once the most common type of lung cancer. However, in the mid 1970s, there was a shift toward adenocarcinoma, which today is the most common lung cancer cell type and the predominant type found in women.14 Whether this change in cell type is caused by a change in the contents of light, low-tar, and women’s cigarettes in unknown.
These observations do not address the basic question of biology, however. The plausible explanations for physiological differences in the biology of lung cancer in men and women focus on genetic susceptibility, the possible role of hormones, nicotine metabolism, the individual cell’s ability to repair damaged DNA, and p-450 enzyme systems.10,14,15
Women and Tobacco
The landmark 1964 Surgeon General’s report on smoking and health causally linked smoking and lung cancer in men.16 Four years later, the 1968 Surgeon General’s report detailed this same association for women. The fact is that 90% of lung cancers are tobacco-related, making lung cancer a very preventable disease.1 Thus, any discussion of prevention mandates discussion of smoking trends.
In the early 1920s, less than 6% of American women smoked. This number steadily increased and peaked in the mid 1960s, when 34% of adult women smoked. Although 50% of men smoked in the 1960s, the number quickly dropped to 37% by 1979 and 26% by the mid 1980s. By the mid 1990s, the rate of smoking among women dropped to approximately 1 in 5.17 The current smoking rates are holding steady at 22% for women and 26% for men.1 The incidence of lung cancer, however, reflects those earlier smoking patterns. This explains, in part, why lung cancer is still on the rise for women while it is declining for men, who were already starting to give up cigarettes in the mid 1950s. Today, more than 50% of high school students have tried a cigarette, and 20% are smokers (ie, smoked on 1 or more of the 30 days preceding the survey).18 In the past, smoking was more common among boys; but now the difference between the smoking rates of boys and girls is only a few percentage points.18 Smoking among adolescents is a concern because most adults begin smoking as youths.
Many girls believe that smoking can help them control their weight and improve their mood; thus, they have a positive association with smoking.1 This leaves these girls very vulnerable to the marketing tactics of the tobacco industry, which in 2001 spent $39 for every person in the country on advertising and promotional activities.19
Both in the United States and around the world, cigarette marketing toward women and girls is laced with images of glamorous, slim models to associate smoking with social desirability and women’s equality (eg, “You’ve come a long way, baby”).1
However, there are effective counters to this industry’s efforts. The Minnesota Target Market campaign, which began in 2000, specifically reached out to adolescents in Minnesota to raise awareness about the risks of tobacco use. By mid 2003, 84% of 12- to 17-year-old girls were aware of the campaign’s messages. In July 2003, the funding for the program dropped from $24 million to $5 million. By the end of 2003, awareness had fallen to 58%, and susceptibility to cigarette smoking jumped from 42% to 51% among girls in this age group.20
Prevention and Treatment
Lung cancer is a priority women’s health issue that must be addressed comprehensively through research, economics, education, and social action. We need to do clinical investigations to learn about the molecular mechanisms of lung cancer in women. This will open the door to new approaches to treatment. Education is needed, especially among the most vulnerable population—youths. Education does work, as demonstrated by the Florida Tobacco Pilot Program, which provided anti-tobacco marketing and education and was responsible for cutting smoking among middle school girls by 40% from 1998 to 2000.17 Tobacco-control strategies, such as legislated smoking bans have been shown to reduce smoking. This has been proven in California, where residents voted in 1988 to increase the state’s surtax on cigarettes by 25 cents a pack to fund tobacco-related education, research, and care for the indigent and which banned smoking in workplaces in 1994. The prevalence of smoking decreased, and women in California are enjoying the benefit. In contrast to the rest of the nation, the incidence of lung cancer in women in California has dropped during the last few years.17
There is no effective screening for early-stage lung cancer, so prevention is the key to decreasing the incidence of this disease. From a clinical standpoint, asking patients about their smoking habits should be a routine part of every health interview. This will identify individuals at risk and open the door for discussion about the consequences of smoking and the availability of smoking-cessation programs. Although it will take a concerted effort on all levels to bring the disease among women under control, this simple step is one way physicians can make an impact. MM
Mary Boylan is a cardiothoracic surgeon with St. Luke’s Cardiothoracic Surgery Associates in Duluth.
References
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20. Centers for Disease Control and Prevention. Effect of Ending Antitobacco Youth Campaign on Adolescent Susceptibility to Cigarette Smoking—Minnesota, 2002-2003. MMWR April 16, 2004;53(14);301-4.