Measuring the projected public health impact of lung cancer through lifetime and age-conditional risk estimates

Impact of reduced patient life expectancy on potential cancer risks from radiologic imaging

PURPOSE

To quantify the effect of reduced life expectancy on cancer risk by comparing estimated lifetime risks of lung cancer attributable to radiation from commonly used computed tomographic (CT) examinations in patients with and those without cancer or cardiac disease.

MATERIALS AND METHODS

With the use of clinically determined life tables, reductions in radiation-attributable lung cancer risks were estimated for coronary CT angiographic examinations in patients with multivessel coronary artery disease who underwent coronary artery bypass graft (CABG) surgery and for surveillance CT examinations in patients treated for colon cancer. Statistical uncertainties were estimated for the risk ratios in patients who underwent CABG surgery and patients with colon cancer versus the general population.

RESULTS

Patients with decreased life expectancy had decreased radiation-associated cancer risks. For example, for a 70-year-old patient with colon cancer, the estimated reduction in lifetime radiation-associated lung cancer risk was approximately 92% for stage IV disease, versus 8% for stage 0 or I disease. For a patient who had been treated with CABG surgery, the estimated reduction in lifetime radiation-associated lung cancer risk was approximately 57% for a 55-year-old patient, versus 12% for a 75-year-old patient.

CONCLUSION

The importance of radiation exposure in determining optimal imaging usage is much reduced for patients with markedly reduced life expectancies: Imaging justification and optimization criteria for patients with substantially reduced life expectancies should not necessarily be the same as for those with normal life expectancies.

Demographical analyses of lung cancer incidence and mortality trends in Vojvodina

BACKGROUND: Studies conducted in Vojvodina from 1960 to 1978 showed that the highest number and percentage of lung cancer cases and deaths occurred in seventh decade of life. Our aim was to analyze epidemiological characteristics of lung cancer in Vojvodina demographically from 1989 to 1998. METHODS: Data used for analyses were provided by the Cancer Registry of Vojvodina from the Institute of Oncology Sremska Kamenica. Descriptive epidemiological method was used. RESULTS: The sex ratio (males to females) of lung cancer incidence in Vojvodina is 5.14. Our study showed that the most unfavorable lung cancer incidence trends were present in age groups ranged from 45 to 49, 60 to 64, 65 to 69, and 70 to 74 years in men and in age groups ranged from 35 to 39, 40 to 44, and 45 to 49 years in women. We also found that the most unfavorable lung cancer mortality trends were present in age groups ranged from 45 to 49, 60 to 64, 65 to 69, and 70 to 74 years in men and in age groups range from 45 to 49 and 70 to 74 years in women. Favorable lung cancer mortality and incidence trend was present only in the age group ranged from 80 to 84 years in men. The highest percentage of diseased and deaths was in the age group ranged from 60 to 69 years for both sexes. In younger age groups the percentage of diseased was less than 2%. CONCLUSION: Preventive measures against lung cancer in our population do not show good results yet. This is either because of greater exposure of population to the risk factors or because of greater exposure to the risk factors of certain age cohorts. Decrease in sex ratio has shown that females are closing onto males when we talk about numbers of new lung cancer cases. It is clear that lung cancer incidence trends in males by age groups has shown greater variability while in females variability occurs on smaller scale when lung cancer incidence trends by age groups are discussed.

Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer

PURPOSE

To estimate the radiation-related lung cancer risks associated with annual low-dose computed tomographic (CT) lung screening in adult smokers and former smokers, and to establish a baseline risk that the potential benefits of such screening should exceed.

MATERIALS AND METHODS

The estimated lung radiation dose from low-dose CT lung examinations corresponds to a dose range for which there is direct evidence of increased cancer risk in atomic bomb survivors. Estimated dose-, sex-, and smoking status-dependent excess relative risks of lung cancer were derived from cancer incidence data for atomic bomb survivors and used to calculate the excess lung cancer risks associated with a single CT lung examination at a given age in a U.S. population. From these, the overall radiation risks associated with annual CT lung screening were estimated.

RESULTS

A 50-year-old female smoker who undergoes annual CT lung screening until age 75 would incur an estimated radiation-related lung cancer risk of 0.85%, in addition to her otherwise expected lung cancer risk of approximately 17%. The radiation-associated cancer risk to other organs would be far lower. If 50% of all current and former smokers in the U.S. population aged 50-75 years received annual CT screening, the estimated number of lung cancers associated with radiation from screening would be approximately 36,000, a 1.8% (95% credibility interval: 0.5%, 5.5%) increase over the otherwise expected number.

CONCLUSION

Given the estimated upper limit of a 5.5% increase in lung cancer risk attributable to annual CT-related radiation exposure, a mortality benefit of considerably more than 5% may be necessary to outweigh the potential radiation risks.

Respiratory cancer risks associated with low-level nickel exposure: an integrated assessment based on animal, epidemiological, and mechanistic data

Increased lung and nasal cancer risks have been reported in several cohorts of nickel refinery workers, but in more than 90% of the nickel-exposed workers that have been studied there is little, if any evidence of excess risk. This investigation utilizes human exposure measurements, animal data from cancer bioassays of three nickel compounds, and a mechanistic theory of nickel carcinogenesis to reconcile the disparities in lung cancer risk among nickel-exposed workers. Animal data and mechanistic theory suggest that the apparent absence of risk in workers with low nickel exposures is due to threshold-like responses in lung tumor incidence (oxidic nickel), tumor promotion (soluble nickel), and genetic damage (sulfidic nickel). When animal-based lung cancer dose-response functions for these compounds are extrapolated to humans, taking into account interspecies differences in deposition and clearance, differences in particle size distributions, and human work activity patterns, the predicted risks at occupational exposures are remarkably similar to those observed in nickel-exposed workers. This provides support for using the animal-based dose-response functions to estimate occupational exposure limits, which are found to be comparable to those in current use.

Epidemiology, etiology, and prevention of lung cancer

Over the past century, lung cancer has gone from an obscure disease to the leading cause of cancer death worldwide. Initially an epidemic disease among men in industrialized nations, lung cancer now has become the leading cancer killer in both sexes in the United States and an increasingly common disease of both sexes in developing countries. Lung cancer incidence largely mirrors smoking prevalence, with a latency period of several decades. Other important risk factors for the development of lung cancer include environmental exposure to tobacco smoke, radon, occupational carcinogens, and pre-existing nonmalignant lung disease. Studies in molecular biology have elucidated the role that genetic factors play in modifying an individual's risk for lung cancer. Although chemopreventive agents may be developed to prevent lung cancer, prevention of smoking initiation and promotion of smoking cessation are currently the best weapons to fight lung cancer. No other malignancy has been shown to have such a strong epidemiologic relation between a preventable behavior and incidence of disease. Despite this knowledge, more than 20% of all Americans smoke, and tobacco use is exploding in developing countries. Based on current and projected smoking patterns, it is anticipated that lung cancer will remain the leading cause of cancer death in the world for decades to come.