Projection of future numbers of mesothelioma cases in the US and the increasing prevalence of background cases: an update based on SEER data for 1975 through 2018

Abstract

Historically, mesothelioma, which is almost exclusively a cancer of the pleura or peritoneum, has been referred to as a sentinel disease for asbestos exposure meaning that the disease is an epidemiologic marker for asbestos. This description of mesothelioma often has been misinterpreted to mean that the only risk factor for mesothelioma is asbestos. In addition to a few risk factors other than asbestos, in the US, background mesotheliomas, i.e. mesothelioma cases that are a consequence of spontaneous tumor formation, are the most prevalent number of cases after asbestos-associated cases.¹ My analysis of SEER data for 1973 through 2005 published in 2009 projected that around 2040 virtually all mesothelioma cases in the US will be background cases. The update here, which is based on the most current SEER data, 1975 through 2018, and the same methods used in 2009 shows that the pattern of mesothelioma incidence is unchanged. Further, in general agreement with the analysis published in 2009, after 2040 virtually all mesothelioma cases, currently estimated to be approximately 1600 per year, will be background cases.

Keywords:

• Mesothelioma
• asbestos cases
• background cases
• age birth cohort model
• future numbers of cases

Acknowledgement

I thank the three reviewers for their insightful comments which have led to revisions and additions that improved my article.

Declaration of interest

Noting the many references in the peer review literature to my article “Time trend of mesothelioma incidence in the United States and projection of future cases: An update based on SEER data for 1973 through 2005,” Critical Reviews in Toxicology, 2009; 39(7): 576–588 which was based on SEER data through 2005, I thought an update was justified using the most current SEER data, 1975 through 2018.

I received no financial support for the analysis or for the preparation of my article.

I have been a consultant concerning asbestos issues to companies that mined talc and vermiculite and to former manufacturers of asbestos-containing products. I have testified in legal proceeding at the request of former manufactures of asbestos-containing products on asbestos exposure and the risk of asbestos-associated disease.

Notes

1 Some researchers use “background” to refer to cases that are a consequence of exposure to the typically low ambient levels of asbestos. “Background” in this article means not caused by asbestos or any other known risk factor for the disease; also referred to as spontaneous tumor formation.

2 This estimate is based on total US deaths before 2020 when Covid deaths began to add significantly to the annual number of US deaths.

3 Age-adjusted incidence data makes possible unbiased comparisons of the incidence of a disease that may depend on age across groups with different age distributions. All other things being equal, the risk of mesothelioma increases with age. Age-adjusted incidence allows unbiased comparisons of incidence across years.

4 The incidence data in Figure 1 are the sum of pleural plus peritoneal mesothelioma for the 18 cancer registries contributing data to the SEER database at the time of the analysis presented here. The SEER database includes mesothelioma at other anatomical sites, e.g. pericardium and testis. However, mesothelioma of the pleura and peritoneum make up the vast majority of mesothelioma cases in the SEER database. The sum of cases at these two sites does not distort the trend of cases (see Discussion section).

5 36 FR 23207

6 37 FR 11318; 51 FR 22612; 59 FR 40964

7 One exception to this characterization of asbestos exposure for women is a group who were exposed to asbestos at the same high occupational levels experienced by men. Starting in 1940, coinciding with World War II, between 5 and 6 million women went to work in heavy industry; early in 1944, 2.7 million women were employed as factory workers; within a year after the end of the war, 3.5 million women left the labor force (Lane 1951).

8 A diagnostic effect is an increase in the number of mesothelioma cases diagnosed due to increased awareness about the disease, which was likely around 1982 because of publicity concerning EPA’s program concerning asbestos in schools and the Agency’s expression of concern about the disease potential associated with asbestos exposure. EPA regulations requiring school inspections for asbestos-containing materials were promulgated in 1982 (47 FR 23360)

9 Background rates for women are estimated as the number of female cases predicted for the US by the model (Figure 2) divided by the total number of US females ages 15 and older. Lifetime risk is an estimate produced in a survival analysis. (See the Materials and Methods section.)

10 Female Asbestos: 10% of women born between 1900 and 1924 worked in high asbestos exposure jobs during WWII; subsequently, 0.1% of women born between 1925 and 1959 worked in high asbestos exposure jobs. These parameter values were developed from data in Lane (1951). The number of female background cases is estimated as all female cases minus female asbestos cases. Male Asbestos: The number of male background cases is the same as the number of female background cases. Therefore, the number of male asbestos cases is the number of all male mesothelioma cases minus the number of female background cases.