Head and neck tumors associated with cell phone use have increased in the U.S. since 2000 (updated 6/3/2024)
The increase in age-adjusted incidence rates for these four tumors may be attributable to the chronic effects of mobile phone use in addition to increased exposure to other risk factors as well as improvements in diagnostic screening and reporting.
The following data on tumor incidence rates are from the National Cancer Institute's SEER 22 Registry which covers 48% of the total U.S. population. The data were age-adjusted to the population in the year 2000 so observed differences over time are not affected by changes in the age composition of the population.
Nonmalignant Meningioma
In the U.S. nonmalignant meningioma, a tumor that forms on the outer covering of the brain, is the most common brain tumor. The incidence of this tumor was not reported to the SEER registry prior to 2004.
The age-adjusted incidence rate of nonmalignant meningioma of the brain and nervous system significantly increased overall in the U.S. by 73% from 2004 (6.62 per 100,000) to 2021 (11.43 per 100,000). From 2004 to 2006 the increase was 12.67% per year, and from 2006 to 2021 the increase was 2.07% per year. The increase occurred in all age groups.
Thyroid Cancer
The age-adjusted incidence rate of thyroid cancer significantly increased overall in the U.S. by 79% from 2000 (7.59 per 100,000) to 2021 (13.57 per 100,000). The rate significantly increased from 2000 to 2009 by 7.16% per year and from 2009 to 2014 by 1.90% per year, and has decreased from 2014-2021 by 1.91% per year.
Salivary Gland Cancer
The age-adjusted incidence rate of salivary gland cancer significantly increased overall in the U.S. by 13% from 2000 (1.22 per 100,000) to 2021 (1.38 per 100,000). The rate significantly increased by 0.58% per year during this time period.
Reference: SEER*Explorer: An
interactive website for SEER cancer statistics [Internet]. Surveillance
Research Program, National Cancer Institute; 2024 Apr 17. [cited 2024 May 31].
Available from: https://seer.cancer.gov/statistics-network/explorer/. Data
source(s): SEER Incidence Data, November 2023 Submission (1975-2021), SEER 22
registries.
Hardell and Carlberg (2015) reported that brain tumor rates have been increasing in Sweden based upon the Swedish National Inpatient Registry data. Hardell and Carlberg (2017) reported that brain tumors of unknown type increased from 2007-2015, especially in the age group 20-39 years of age. According to the authors, "This may be explained by higher risk for brain tumor in subjects with first use of a wireless phone before the age of 20 years taking a reasonable latency period."
What about brain tumor rates in the United States?
The incidence of glioma, the most common malignant brain tumor, has increased in the United States, although not across-the-board. The National Cancer Institute reported that glioma incidence in the frontal lobe increased among young adults 20-29 years of age (Inskip et al., 2010).
The incidence of glioblastoma multiforme (GBM), which accounts for about half of all gliomas, increased in the frontal and temporal lobes, and in the cerebellum among adults in the U.S. from 1992-2006 (Zada et al., 2012).
The Cancer Prevention Institute of California (2016) in their annual report about cancer incidence in the greater San Francisco Bay Area noted that the incidence of GBM increased from 1988-2013 among non-Hispanic white male (0.7% per year) and female adults (1.1% per year) and remained stable among other race/ethnic groups.
Using national tumor registry data, a recent study found that the overall incidence of meningioma, the most common non-malignant brain tumor, has increased in the United States in recent years (Dolecek et al., 2015). The age-adjusted incidence rate for meningioma increased from about 6.3 per 100,000 in 2004 to about 7.8 per 100,000 in 2009. Brain tumor incidence increased for all age groups except youth (0-19 years of age).
Risk of glioma from cell phone and cordless phone use
Three independent, case-control studies have found that long-term use of cell phones increases risk for glioma (Interphone Study Group, 2010; Hardell et al, 2013; Coureau et al, 2014). The only research to examine cordless phone use also found increased glioma risk with long-term use (Hardell et al, 2013). These studies include data from 13 nations: Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the UK. After ten years of wireless phone use (i.e., cell phone plus cordless phone use), the risk of glioma doubles and after 25 years, the risk triples (Hardell et al, 2013).
Although the U.S. does not conduct research on wireless phone use and tumor risk in humans and does not participate in the international studies, there is no reason to believe that Americans are immune to these potential effects of wireless phone use.
In sum, the peer-reviewed research on brain tumor risk and wireless phone use strongly suggests that we should exercise precaution and keep cell phones and cordless phones away from our heads. Moreover, the research calls into question the adequacy of national and international guidelines that limit the amount of microwave radiation emitted by cell phones and cordless phones.
Two earlier case-control studies conducted in other nations have found significant evidence of increased risk for meningioma among heavy cell phone users:
(2) In Australia, Canada, France, Israel and New Zealand, Cardis et al. (2011) found a two-fold greater risk of meningioma for heavy cell phone users (defined as 3,124 or more hours of lifetime use) (OR = 2.01; 95% CI = 1.03 to 2.93).
The two prior studies did not assess cordless phone use so it's likely they underestimate the meningioma risk from wireless phone use.
Thus, three independent, case-control studies have found that wireless phone use is a risk factor for meningioma.
(updated August 1, 2021)
Background: The American Cancer Society, Centers for Disease Control and Prevention, National Cancer Institute, and North American Association of Central Cancer Registries collaborate to provide annual updates on cancer incidence and mortality and trends by cancer type, sex, age group, and racial/ethnic group in the United States. In this report, we also examine trends in stage-specific survival for melanoma of the skin (melanoma).
Methods: Incidence data for all cancers from 2001 through 2017 and survival data for melanoma cases diagnosed during 2001-2014 and followed up through 2016 were obtained from the Centers for Disease Control and Prevention- and National Cancer Institute-funded population-based cancer registry programs compiled by the North American Association of Central Cancer Registries. Data on cancer deaths from 2001 through 2018 were obtained from the National Center for Health Statistics' National Vital Statistics System. Trends in age-standardized incidence and death rates and 2-year relative survival were estimated by joinpoint analysis, and trends in incidence and mortality were expressed as average annual percent change (AAPC) during the most recent 5 years (2013-2017 for incidence and 2014-2018 for mortality).
Results: Overall cancer incidence rates (per 100,000 population) for all ages during 2013-2017 were 487.4 among males and 422.4 among females. During this period, incidence rates remained stable among males but slightly increased in females (AAPC = 0.2%; 95% confidence interval [CI] = 0.1% to 0.2%). Overall cancer death rates (per 100,000 population) during 2014-2018 were 185.5 among males and 133.5 among females. During this period, overall death rates decreased in both males (AAPC = -2.2%; 95% CI = -2.5% to - 1.9%) and females (AAPC = -1.7%; 95% CI = -2.1% to - 1.4%); death rates decreased for 11 of the 19 most common cancers among males and for 14 of the 20 most common cancers among females, but increased for 5 cancers in each sex. During 2014-2018, the declines in death rates accelerated for lung cancer and melanoma, slowed down for colorectal and female breast cancers, and leveled off for prostate cancer. Among children younger than age 15 years and adolescents and young adults aged 15-39 years, cancer death rates continued to decrease in contrast to the increasing incidence rates. Two-year relative survival for distant-stage skin melanoma was stable for those diagnosed during 2001-2009 but increased by 3.1% (95% CI = 2.8% to 3.5%) per year for those diagnosed during 2009-2014, with comparable trends among males and females.
Conclusions: Cancer death rates in the United States continue to decline overall and for many cancer types, with the decline accelerated for lung cancer and melanoma. For several other major cancers, however, death rates continue to increase or previous declines in rates have slowed or ceased. Moreover, overall incidence rates continue to increase among females, children, and adolescents and young adults. These findings inform efforts related to prevention, early detection, and treatment and for broad and equitable implementation of effective interventions, especially among under-resourced populations.
"Among females, incidence rates increased during 2013-2017 for 8 of the 18 most common cancers: liver, melanoma, kidney, myeloma, corpus and uterus, not otherwise specified (uterus), pancreas, breast, and oral cavity and pharynx; were stable for 4 cancers: cervix, leukemia, stomach, and NHL; and decreased for 6 cancers: thyroid, ovary, lung, colorectum, bladder, and brain and ONS (Figure 3, Table 1). However, liver cancer incidence rates among females stabilized during 2014-2017 (Table 2)."
Children aged 0-14 years:
Adolescents and young adults [AYA] aged 15-39 years:
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- Childhood
cancer varies geographically. This research may help states assess their
needs in order to make sure that cancer patients have access to high
quality cancer treatment and long-term care to monitor for side effects of
their treatment after they have completed therapy.
- Overall,
we found a slight increase in pediatric cancer from 2001 to 2014. Cancer was increasing for lymphoma,
thyroid, brain, kidney, and liver cancer and was decreasing for
melanoma. This study could help researchers more effectively study why
pediatric cancer is increasing or decreasing and why certain groups of
children and adolescents are more affected.
Abstract
PURPOSE: Reasons for worldwide variability in the burden of primary malignant brain and central nervous system (CNS) tumors remain unclear. This study compares the incidence and survival of malignant brain and CNS tumors by selected histologic types between the United States (US) and Taiwan.
METHODS: Data from 2002 to 2010 were selected from two population-based cancer registries for primary malignant brain and CNS tumors: theCentral Brain Tumor Registry of the United States and the Taiwan Cancer Registry. Two registries had similar process of collecting patients with malignant brain tumor, and the quality of two registries was comparative. The age-adjusted incidence rate (IR), IR ratio, and survival by histological types, age, and gender were used to study regional differences.
RESULTS: The overall age-adjusted IRs were 5.91 per 100,000 in the US and 2.68 per 100,000 in Taiwan. The most common histologic type for both countries was glioblastoma (GBM) with a 12.9% higher proportion in the US than in Taiwan. GBM had the lowest survival rate of any histology in both countries (US 1-year survival rate = 37.5%; Taiwan 1-year survival rate = 50.3%). The second largest group was astrocytoma, excluding GBM and anaplastic astrocytoma, with the distribution being slightly higher in Taiwan than in the US.
CONCLUSION: Our findings revealed differences by histological type and grade of primary malignant brain and CNS tumors between two sites.
Open access paper: http://www.ncbi.nlm.nih.gov/
Excerpts
Between 2002 and 2010, there were 183,740 newly diagnosed cases of malignant brain and CNS tumors in the US and 5,855 in Taiwan.
The most common histologic group for both countries was GBM; 47.8% of all tumors in the US and 34.9% of all tumors in Taiwan (Figure 3).
The IR of GBM was 2.9 times in the US (2.48 per 100,000) as compared with Taiwan (0.85 per 100,000). The second highest histologic group was astrocytoma (excluding GBM and AA) in both the US (0.95 per 100,000) and Taiwan (0.44 per 100,000).
In the US, the IRs by primary site were highest for tumors located in the frontal lobe (1.34 per 100,000), followed by tumors located in all other sites within the brain, temporal lobe, parietal lobe, and the other parts of brain and CNS. In Taiwan, the IRs were highest for tumors located in all other parts of the brain (0.70 per 100,000), followed by tumors located in the frontal lobe, temporal lobe, and cerebrum.
In this study, the lower age-adjusted IRs of malignant brain and CNS tumors in Taiwan was less likely due to differences in imaging diagnostic techniques as the standards for imaging for brain and CNS tumors was the same in both countries.
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Adolescent and Young Adult Primary Brain and Central Nervous System Tumors Diagnosed in the United States in 2008-2012
Ostrom QT, Gittleman H, de Blank PM, Finlay JL, Gurney JG, McKean-Cowdin R, Stearns DS, Wolff JE, Liu M, Wolinsky Y, Kruchko C, Barnholtz-Sloan JS. American Brain Tumor Association Adolescent and Young Adult Primary Brain and Central Nervous System Tumors Diagnosed in the United States in 2008-2012. Neuro Oncol. 2016 Jan;18 Suppl 1:i1-i50. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690545/
- "Incidence of oligodendroglioma (APC = 22.9) and anaplastic oligodendroglioma (APC = 24.1) in AYA has significantly decreased from 2004-2012.
- Incidence of tumors of the meninges in AYA has significantly increased from 2004-2012 (APC = 2.5), which is largely driven by the increase of meningioma incidence during that time (APC = 2.6).
- Incidence of lymphomas and hematopoietic neoplasms has significantly decreased from 2004-2012 (APC = 22.8) in AYA.
- Incidence of tumors of the sellar region in AYA has significantly increased from 2004-2008 (APC = 8.5), which is largely driven by the increase of tumors of the pituitary incidence from 2004-2009 (APC = 7.6).
- Incidence of unclassified tumors in AYA has significantly increased from 2004-2012 (APC = 5.5), which is largely driven by the increase of hemangioma incidence from 2004-2010 (APC = 18.8)."
Malignant Brain Tumors Most Common Cause of Cancer Deaths in Adolescents & Young Adults
Press Release, American Brain Tumor Association, Feb 24, 2016
A new report published in the journal Neuro-Oncology and funded by the American Brain Tumor Association (ABTA) finds that malignant brain tumors are the most common cause of cancer-related deaths in adolescents and young adults aged 15-39 and the most common cancer occurring among 15-19 year olds.
The 50-page report, which utilized data from the Central Brain Tumor Registry of the United States (CBTRUS) from 2008-2012, is the first in-depth statistical analysis of brain and central nervous system (CNS) tumors in adolescents and young adults (AYA). Statistics are provided on tumor type, tumor location and age group (15-19, 20-24, 25-29, 30-34 and 35-39) for both malignant and non-malignant brain and CNS tumors.
"When analyzing data in 5-year age increments, researchers discovered that the adolescent and young adult population is not one group but rather several distinct groups that are impacted by very different tumor types as they move into adulthood," said Elizabeth Wilson, president and CEO of the American Brain Tumor Association.
"For these individuals -- who are finishing school, pursuing their careers and starting and raising young families -- a brain tumor diagnosis is especially cruel and disruptive," added Wilson. "This report enables us for the first time to zero-in on the types of tumors occurring at key intervals over a 25-year time span to help guide critical research investments and strategies for living with a brain tumor that reflect the patient's unique needs."
Although brain and CNS tumors are the most common type of cancer among people aged 15-19, the report shows how other cancers become more common with age. By ages 34-39 years, brain and CNS tumors are the third most common cancer after breast and thyroid cancer.
"What's interesting is the wide variability in the types of brain tumors diagnosed within this age group which paints a much different picture than what we see in adults or in pediatric patients," explained the study's senior author Jill Barnholtz-Sloan, Ph.D., associate professor, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine and Scientific Principal Investigator for CBTRUS.
"For example, the most common tumor types observed in adults are meningiomas and glioblastomas, but there is much more diversity in the common tumor types observed in the adolescent and young adult population. You also clearly see a transition from predominantly non-malignant and low-grade tumors to predominantly high-grade tumors with increasing age," Barnholtz-Sloan said.
There are nearly 700,000 people in the U.S. living with brain and CNS tumors and approximately 15 percent of these tumors occurred in the AYA population during the 2008-2012 time frame analyzed in this report. Approximately 10,617 brain and CNS tumors are diagnosed among adolescents and young adults each year and are the cause of approximately 434 deaths annually.
"The American Brain Tumor Association's recognition of this understudied population, and their commitment to data and information sharing should be applauded," added Barnholtz-Sloan. "There are clearly unique characteristics of the 15-39 age group that we need to more comprehensively understand and the information in the ABTA report starts that important dialogue."
The full report is available at http://www.abta.org/about-us/
To learn more or access additional statistics, go to http://www.abta.org.
http://bit.ly/1OvDHYy
Brain tumors are the:
- most common cancer among those age 0-19 (leukemia is the second).
- second leading cause of cancer-related deaths in children (males and females) under age 20 (leukemia is the first).
- Nearly 78,000 new cases of primary brain tumors are expected to be diagnosed this year. This figure includes nearly 25,000 primary malignant and 53,000 non-malignant brain tumors.
- It is estimated that more than 4,600 children between the ages of 0-19 will be diagnosed with a primary brain tumor this year.
- There are nearly 700,000 people in the U.S. living with a primary brain and central nervous system tumor.
- This year, nearly 17,000 people will lose their battle with a primary malignant and central nervous system brain tumor.
- There are more than 100 histologically distinct types of primary brain and central nervous system tumors.
- Survival after diagnosis with a primary brain tumor varies significantly by age, histology, molecular markers and tumor behavior.
- The median age at diagnosis for all primary brain tumors is 59 years.
- Meningiomas represent 36.4% of all primary brain tumors, making them the most common primary brain tumor. There will be an estimated 24,880 new cases in 2016.
- Gliomas, a broad term which includes all tumors arising from the gluey or supportive tissue of the brain, represent 27% of all brain tumors and 80% of all malignant tumors.
- Glioblastomas represent 15.1% of all primary brain tumors, and 55.1% of all gliomas.
- Glioblastoma has the highest number of cases of all malignant tumors, with an estimated 12,120 new cases predicted in 2016.
- Astrocytomas, including glioblastoma, represent approximately 75% of all gliomas.
- Nerve sheath tumors (such as acoustic neuromas) represent about 8% of all primary brain tumors.
- Pituitary tumors represent 15.5% of all primary brain tumors. There will be an estimated 11,700 new cases of pituitary tumors in 2016.
- Lymphomas represent 2% of all primary brain tumors.
- Oligodendrogliomas represent nearly 2% of all primary brain tumors.
- Medulloblastomas/embryonal/
primitive tumors represent 1% of all primary brain tumors. - The majority of primary tumors (36.4%) are located within the meninges.
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Central Brain Tumor Registry of the United States: 2018 Fact Sheet
One in 161 Americans (0.62%) will be diagnosed with brain or other central nervous system (CNS) cancer (i.e., malignant tumors) during their lifetime according to the Central Brain Tumor Registry of the United States.
Excerpts
The incidence rate of all primary malignant and non-malignant brain and CNS tumors is 23.03 cases per 100,000 for a total count of 392,982 incident tumors; (7.12 per 100,000 for malignant tumors for a total count of 121,277 incident tumors and 15.91 per 100,000 for non-malignant tumors for a total count of 271,105 incident tumors). The rate is higher in females (25.31 per 100,000 for a total count of 227,834 incident tumors) than in males (20.59 per 100,000 for a total count of 164,148 incident tumors).
An estimated 86,970 new cases of primary malignant and non-malignant brain and CNS tumors are expected to be diagnosed in the United States in 2019. This includes an estimated 26,170 primary malignant and 60,800 non-malignant tumors expected to be diagnosed in the US in 2019.
Pediatric Incidence (Ages 0-14 Years)
The incidence rate of childhood primary malignant and non-malignant brain and CNS tumors in the US is 5.65 cases per 100,000 for a total 5-year count of 17,273 incident tumors. The rate is higher in males (5.84 per 100,000) than females (5.45 per 100,000).
An estimated 3,720 new cases of childhood primary malignant and non-malignant brain and CNS tumors are expected to be diagnosed in the US in 2019.
Adolescent & Young Adult (AYA) Incidence (Ages 15-39 Years)
The incidence rate of AYA primary malignant and non-malignant brain and CNS tumors is 11.2 cases per 100,000 for a total 5-year count of 57,821 incident tumors.1 The rate is higher for non-malignant tumors (7.94 per 100,000) than malignant tumors (3.26 per 100,000).
An estimated 12,290 new cases of AYA primary malignant and non-malignant brain and CNS tumors are expected to be diagnosed in the US in 2019.
Mortality
The average annual mortality rate in the US between 2011 and 2015 was 4.37 per 100,000 with 77,375 deaths attributed to primary malignant brain and CNS tumors.
An estimated 16,830 deaths will be attributed to primary malignant brain and CNS tumors in the US in 2019.
Lifetime Risk
From birth, a person in the US has a 0.62% chance of ever being diagnosed with a primary malignant brain/CNS tumor (excluding lymphomas, leukemias, tumors of pituitary and pineal glands, and olfactory tumors of the nasal cavity) and a 0.47% chance of dying from the primary malignant brain/CNS tumor.
For males in the US, the risk of developing a primary malignant brain/CNS tumor is 0.70%, and the risk of dying from a primary malignant brain/CNS tumor (excluding lymphomas, leukemias, tumors of pituitary and pineal glands, and olfactory tumors of the nasal cavity) is 0.53%.
For females in the US, the risk of developing a primary malignant brain/CNS tumor is 0.54%, and the risk of dying from a primary malignant brain/CNS tumor (excluding lymphomas, leukemias, tumors of pituitary and pineal glands, and olfactory tumors of the nasal cavity) is 0.41%.
Prevalence
The prevalence rate for all malignant primary brain and CNS tumors was estimated to be 47.60 per 100,000. It was estimated that more than 103,634 persons were living with a diagnosis of malignant primary brain and central nervous system tumor in the United States in 2010.
The prevalence rate for all pediatric (ages 0-19) malignant primary brain and central nervous system tumors was estimated at 22.31 per 100,000 with more than 13,657 children estimated to be living with this diagnosis in the United States in 2004.
Note
Estimated numbers of incidence of malignant and non-malignant brain and CNS tumors and deaths due to these tumors were calculated for 2015 and 2016 using age-adjusted annual tumor incidence rates generated for 2000-2012 for non-malignant tumors by state, age, and histologic type.
http://www.cbtrus.org/www.cbtrus.org/factsheet/factsheet.html--
Brain Tumors in Children and Adolescents
According to a recent study, there has been a significant increase in the incidence of primary malignant brain and central nervous system (CNS) tumors in American children (0-14 years of age) between 2000-2010, with an annual percentage change (APC) of 0.6%. In adolescents (15-19 years old), there was a significant increase in the incidence of primary malignant brain and CNS tumors between 2000-2008, with an APC of 1.0%. Adolescents also experienced an increase in non-malignant brain and CNS tumors from 2004-2010, with an APC of 3.9%.
The four-nation CEFALO case-control study found a 36% increased risk of brain tumors among children and adolescents 7-19 years of age who used mobile phones at least once a week for six months. Since this risk estimate was not statistically significant (OR = 1.36; 95% CI = 0.92 to 2.02), the authors dismissed this overall finding. However, in a subsample of 556 youth for whom cell phone company records were available, there was a significant association between the time since first mobile phone subscription and brain tumor risk. Children who used cellphones for 2.8 or more years were twice as likely to have a brain tumor than those who never regularly used cellphones (OR = 2.15, 95% CI = 1.07 to 4.29).
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Trends in Incidence of Non-Malignant Head and Neck Tumors in the U.S.
The likelihood of developing a non-malignant brain tumor has increased in recent years in the U.S. According to newly-released data from the Centers for Disease Control and Prevention (CDC), the overall age-adjusted incidence (per 100,000 persons) of non-malignant brain tumors significantly increased from 2004 through 2012. The increase was observed among children 0-19 years of age (1.7 in 2004; 2.3 in 2012) and among adults 20 years and older (15.9 in 2004; 19.7 in 2012).
A peer-reviewed study reported a significant Increase over time in the incidence of specific types of malignant brain tumors among adults in the U.S. (see May 7, 2015 post below).
A recent study reported a significant increase in meningioma incidence for the period 2004 through 2009 (Dolecek et al., 2015). Several case-control studies have found a significant association between risk of meningioma and wireless phone use (see May 7, 2015 post below).
A prospective study of 790,000 women in the United Kingdom reported that the risk pituitary gland tumors was more than twice as high among women who used a cell phone for less than five years as compared to never users (Benson et al., 2013).
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"Users must be aware of diverse issues that influence collection and interpretation of cancer registry data, such as multiple cancer diagnoses, duplicate reports, reporting delays, misclassification of race/ethnicity, and pitfalls in estimations of cancer incidence rates." (Izqierdo, JN, Schoenbach, VJ. The potential and limitations of data from population-based state cancer registries. Am J Public Health. 2000;90:695-698. URL:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1446235/)
Delays in reporting and late ascertainment are a reality and a known issue influencing registry completeness and, consequently, rate underestimations occur, especially for the most recent years.22 CBTRUS also recognizes that the problem may be even more likely to occur in the reporting of non-malignant brain and CNS tumors, where reporting often comes from non-hospital based sources and mandated collection is relatively recent (2004). Ostrom et al. (2014). URL:For a discussion of the factors that undermine the data quality and completeness of cancer registry coverage of diagnosed tumors see Bray et al (2015), Coebergh et al (2015), and Siesling et al (2015).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4193675/).
The shortcomings of cancer registries are not just hypothetical. For example, Hardell and Carlberg (2015) recently reported that brain cancer rates have been increasing in Sweden based upon the Swedish National Inpatient Registry but not according to the Swedish Cancer Registry. Based upon their results they "postulate(d) that a large part of brain tumours of unknown type are never reported to the Cancer Register ... We conclude that the Swedish Cancer Register is not reliable ..."