Geographic clustering of testicular cancer incidence in the northern part of The Netherlands

State Trends of Cannabis Liberalization as a Causal Driver of Increasing Testicular Cancer Rates across the USA

BACKGROUND

The cause of the worldwide doubling-tripling of testicular cancer rates (TCRs) in recent decades is unknown. Previous cohort studies associated cannabis use with TCR including dose-response relationships but the contribution of cannabis to TCRs at the population level is unknown. This relationship was tested by analyzing annual trends across US states and formally assessed causality. Four US datasets were linked at state level: age-adjusted TCRs from Centers for Disease Control Surveillance Epidemiology and End Results database; drug use data from annual National Survey of Drug Use and Health including 74.1% response rate; ethnicity and median household income data from the US Census Bureau; and cannabinoid concentration data from Drug Enforcement Agency reports. Data was processed in R in spatiotemporal and causal inference protocols.

RESULTS

Cannabis-use quintile scatterplot-time and boxplots closely paralleled those for TCRs. The highest cannabis-use quintile had a higher TCR than others (3.44 ± 0.05 vs. 2.91 ± 0.2, mean ± S.E.M., t = 10.68, p = 1.29 × 10-22). A dose-response relationship was seen between TCR and Δ9-tetrahydrocannabinol (THC), cannabinol, cannabigerol, and cannabichromene (6.75 × 10-9 < p < 1.83 × 10-142). In a multivariate inverse probability-weighted interactive regression including race and ethnic cannabis exposure (ECE), ECE was significantly related to TCR (β-estimate = 0.89 (95%C.I. 0.36, 2.67), p < 2.2 × 10-16). In an additive geospatiotemporal model controlling for other drugs, cannabis alone was significant (β-estimate = 0.19 (0.10, 0.28), p = 3.4 × 10-5). In a full geospatial model including drugs, income and ethnicity cannabinoid exposure was significant (cannabigerol: β-estimate = 1.39 (0.024, 2.53), p = 0.0017); a pattern repeated at two spatial and two temporal lags (cannabigerol: β-estimate = 0.71 (0.05, 1.37), p = 0.0.0350; THC: β-estimate = 23.60 (11.92, 35.29), p = 7.5 × 10-5). 40/41 e-Values > 1.25 ranged up to 1.4 × 1063 and 10 > 1000 fitting causal relationship criteria. Cannabis liberalization was associated with higher TCRs (ChiSqu. = 312.2, p = 2.64 × 10-11). Rates of TC in cannabis-legal states were elevated (3.36 ± 0.09 vs. 3.01 ± 0.03, t = 4.69, p = 4.86 × 10-5).

CONCLUSIONS

Cannabis use is closely and causally associated with TCRs across both time and space and higher in States with liberal cannabis legislation. Strong dose-response effects were demonstrated for THC, cannabigerol, cannabinol, cannabichromene and cannabidiol. Cannabinoid genotoxicity replicates all major steps to testicular carcinogenesis including whole-genome doubling, chromosomal arm excision, generalized DNA demethylation and chromosomal translocations thereby accelerating the pathway to testicular carcinogenesis by several decades.

Causal inference multiple imputation investigation of the impact of cannabinoids and other substances on ethnic differentials in US testicular cancer incidence

Background

Ethnic differences in testicular cancer rates (TCRs) are recognized internationally. Cannabis is a known risk factor for testicular cancer (TC) in multiple studies with dose-response effects demonstrated, however the interaction between ancestral and environmental mutagenic effects has not been characterized. We examined the effects of this presumed gene-environment interaction across US states.

Methods

State based TCR was downloaded from the Surveillance Epidemiology and End Results (SEER) website via SEERStat. Drug use data for cigarettes, alcohol use disorder, analgesics, cannabis and cocaine was taken from the National Survey of Drug Use and Health a nationally representative study conducted annually by the Substance Abuse and Mental Health Services Administration (SAMHSA) with a 74.1% response rate. Cannabinoid concentrations derived from Drug Enforcement Agency publications. Median household income and ethnicity data (Caucasian-American, African-American, Hispanic-American, Asian-American, American-Indian-Alaska-Native-American, Native-Hawaiian-Pacific-Islander-American) was from the US Census Bureau. Data were processed in R using instrumental regression, causal inference and multiple imputation.

Results

1975–2017 TCR rose 41% in African-Americans and 78.1% in Caucasian-Americans; 2003–2017 TCR rose 36.1% in Hispanic-Americans and 102.9% in Asian-Pacific-Islander-Americans. Ethnicity-based scatterplot-time and boxplots for cannabis use and TCR closely mirrored each other. At inverse probability-weighted interactive robust regression including drugs, income and ethnicity, ethnic THC exposure was the most significant factor and was independently significant (β-estimate = 4.72 (2.04, 7.41), P = 0.0018). In a similar model THC, and cannabigerol were also significant (both β-estimate = 13.87 (6.33, 21.41), P = 0.0017). In additive instrumental models the interaction of ethnic THC exposure with Asian-American, Hispanic-American, and Native-Hawaiian-Pacific-Islander-American ethnicities was significant (β-estimate = − 0.63 (− 0.74, − 0.52), P = 3.6 × 10^− 29, β-estimate = − 0.25 (− 0.32, − 0.18), P = 4.2 × 10^− 13, β-estimate = − 0.19 (− 0.25, − 0.13), P = 3.4 × 10^− 9). After multiple imputation, ethnic THC exposure became more significant (β-estimate = 0.68 (0.62, 0.74), P = 1.80 × 10^− 92). 25/33 e-Values > 1.25 ranging up to 1.07 × 10⁵. Liberalization of cannabis laws was linked with higher TCR’s in Caucasian-Americans (β-estimate = 0.09 (0.06, 0.12), P = 6.5 × 10^− 10) and African-Americans (β-estimate = 0.22 (0.12, 0.32), P = 4.4 × 10^− 5) and when dichotomized to illegal v. others (t = 6.195, P = 1.18 × 10^− 9 and t = 4.50, P = 3.33 × 10^− 5).

Conclusion

Cannabis is shown to be a TC risk factor for all ethnicities including Caucasian-American and African-American ancestries, albeit at different rates. For both ancestries cannabis legalization elevated TCR. Dose-response and causal relationships are demonstrated.

Testicular Cancer Incidence and Mortality Within Rural and Urban Regions

Purpose: Testicular cancer (TCa) is among the most common cancers within adolescent and young adult (AYA) male populations. However, information is limited to variations in incidence and mortality outside of racial/ethnic subgroups. Rural regions historically have a greater overall cancer incidence than urban regions, although some key differences exist regarding site. TCa-specific incidence and mortality disparities are not commonly reported in this context. This study aims to help fill that gap by providing discovery evidence if there is an association between US rural/urban regions and TCa incidence and mortality. Methods: Secondary analysis of Surveillance, Epidemiology, and End Results incidence and mortality data were employed to determine if rural/urban TCa incidence and mortality disparities exist among U.S. males. Results: There was a 2.6% increased rate of TCa in U.S. urban as compared with rural geographic regions from 2011 to 2015. When geographic region is disaggregated, rural regions see higher rates than urban. When factoring in race/ethnicity, White/Caucasians and Hispanics had statistically higher urban rates whereas American Indian/Alaskan Natives and Asian/Pacific Islander groups had statistically higher rural rates. Conclusion: Geographic regional TCa variation research is virtually nonexistent for U.S. males, specifically AYAs of color. Determining preliminary trends in rural and urban regions can assist in the creation of more targeted services, particularly among underserved and vulnerable populations that have tenuous access to health care, to reduce disparate health outcomes. Exploring geographic differences in TCa incidence and mortality can have implications within service industry, health care accessibility, and public health justice areas of research and outreach.

Environmental Factors Affecting Growth and Occurrence of Testicular Cancer in Childhood: An Overview of the Current Epidemiological Evidence

Testicular cancer (TC) is the most frequently occurring malignancy among adolescents and young men aged 15–34 years. Although incidence of TC has been growing over the past 40 years in several western countries, the explanations for this increase still remain uncertain. It has been postulated that early life exposure to numerous occupational and environmental estrogenic chemicals, such as endocrine-disrupting chemicals (EDCs), may play a contributing role in the etiology of TC, but the subject is still open to additional investigation. Recently, it has also been suggested that prenatal and postnatal environmental exposures associated with child growth and development might also be involved in TC progression. This review of current epidemiological studies (2000–2015) aims to identify environmental factors associated with TC, with a particular focus on infancy and childhood factors that could constitute a risk for disease development. It may also contribute towards recognizing gaps in knowledge and recent research requirements for TC, and to point out possible interactions between child growth and development in relation to prenatal and postnatal environmental exposures.

Etiology and early pathogenesis of malignant testicular germ cell tumors: towards possibilities for preinvasive diagnosis

Malignant testicular germ cell tumors (TGCT) are the most frequent cancers in Caucasian males (20-40 years) with an 70% increasing incidence the last 20 years, probably due to combined action of (epi)genetic and (micro)environmental factors. It is expected that TGCT have carcinoma in situ(CIS) as their common precursor, originating from an embryonic germ cell blocked in its maturation process. The overall cure rate of TGCT is more than 90%, however, men surviving TGCT can present long-term side effects of systemic cancer treatment. In contrast, men diagnosed and treated for CIS only continue to live without these long-term side effects. Therefore, early detection of CIS has great health benefits, which will require an informative screening method. This review described the etiology and early pathogenesis of TGCT, as well as the possibilities of early detection and future potential of screening men at risk for TGCT. For screening, a well-defined risk profile based on both genetic and environmental risk factors is needed. Since 2009, several genome wide association studies (GWAS) have been published, reporting on single-nucleotide polymorphisms (SNPs) with significant associations in or near the genes KITLG, SPRY4, BAK1, DMRT1, TERT, ATF7IP, HPGDS, MAD1L1, RFWD3, TEX14, and PPM1E, likely to be related to TGCT development. Prenatal, perinatal, and postnatal environmental factors also influence the onset of CIS. A noninvasive early detection method for CIS would be highly beneficial in a clinical setting, for which specific miRNA detection in semen seems to be very promising. Further research is needed to develop a well-defined TGCT risk profile, based on gene-environment interactions, combined with noninvasive detection method for CIS.

Studying the impact of early life exposures to pesticides on the risk of testicular germ cell tumors during adulthood (TESTIS project): study protocol

BACKGROUND

The incidence of testicular germ cell tumors (TGCT), the most common cancer in men aged 15 to 45 years, has doubled over the last 30 years in developed countries. Reasons remain unclear but a role of environmental factors, especially during critical periods of development, is strongly suspected. Reliable data on environmental exposure during this critical time period are sparse. Little is known on whether it could be a combined effect of early and later-life exposures.

METHODS/DESIGN

Our research aims to study the association between TGCT risk and pesticide exposures (domestic, occupational and environmental) during critical time periods of development and combined early and later-life exposures. The study design, developed during a 2-year pilot study, is a multicenter case-control study of 500 cases (ascertained through histology) and 1000 fertile/fecund controls recruited through 21 French 'Centres d'Etude et de Conservation des Œufs et de Sperme humain' (CECOS). Trained professional interviewers interview the subjects and their mothers by phone. Using a geographic information system developed and tested for application in this study design, environmental pesticides exposure assessment is based on life-time residential history. Occupational pesticides exposures are assessed by an industrial hygienist based on parents' occupations and tasks. Exposures during the prenatal period, early childhood and puberty are focused. A blood sample is collected from each participant to assess genetic polymorphisms known to be associated with TGCT risk, as well as to explore gene-environment interactions.

DISCUSSION

The results of our study will contribute to better understanding the causes of TGCT and the rapid increase of its incidence. We explore the effect of combined early and later-life pesticides exposure from multiple sources, as well as potential gene-environment interactions that have until now been rarely studied for TGCT. Our design allows future pooled studies and the bio-bank allows additional genetic or toxicological analyses.

Occupational and environmental exposures associated with testicular germ cell tumours: systematic review of prenatal and life-long exposures

Background

Testicular germ cell tumours (TGCT) are the most common cancers in men aged between 15 and 44 years and the incidence has increased steeply over the past 30 years. The rapid increase in the incidence, the spatial variation and the evolution of incidence in migrants suggest that environmental risk factors play a role in TGCT aetiology. The purpose of our review is to summarise the current state of knowledge on occupational and environmental factors thought to be associated with TGCT.

Methods

A systematic literature search of PubMed. All selected articles were quality appraised by two independent researchers using the ‘Newcastle-Ottawa Quality Assessment Scale’.

Results

After exclusion of duplicate reports, 72 relevant articles were selected; 65 assessed exposure in adulthood, 7 assessed parental exposures and 2 assessed both. Associations with occupation was reported for agricultural workers, construction workers, firemen, policemen, military personnel, as well as workers in paper, plastic or metal industries. Electromagnetic fields, PCBs and pesticides were also suggested. However, results were inconsistent and studies showing positive associations tended to had lower quality ranking using the assessment scale (p=0.02).

Discussion

Current evidence does not allow concluding on existence of any clear association between TGCT and adulthood occupational or environmental exposure. The limitations of the studies may partly explain the inconsistencies observed. The lack of association with adulthood exposure is in line with current hypotheses supporting the prenatal origin of TGCT. Future research should focus on prenatal or early life exposure, as well as combined effect of prenatal and later life exposure. National and international collaborative studies should allow for more adequately powered epidemiological studies. More sophisticated methods for assessing exposure as well as evaluating gene–environment interactions will be necessary to establish clear conclusion.

Ethnic and socioeconomic trends in testicular cancer incidence in New Zealand

Ethnic differences in testicular cancer incidence within countries are often sizeable, with white populations consistently having the highest ethnic-specific rates. Many studies have found that high socioeconomic status is a risk factor for testicular cancer. The objectives of this article are to test whether trends in testicular cancer incidence have varied by ethnicity and socioeconomic position in New Zealand between 1981 and 2004. Five cohorts of the entire New Zealand population for 1981-1986, 1986-1991, 1991-1996, 1996-2001 and 2001-2004 were created, and probabilistically linked to cancer registry records, allowing direct determination of ethnic and household income trends in testicular cancer incidence. There were more than 2,000 cases of testicular cancer over the study period. We found increasing rates of testicular cancer for all ethnic and income groups since 1990s. Maori had higher rates, and Pacific and Asian lower rates than European/other men with rate ratios pooled over time of 1.51 (95% CI 1.31-1.74), 0.40 (95% CI 0.26-0.61) and 0.54 (95% CI 0.31-0.94), respectively. Overall, men with low incomes had higher risk of testicular cancer than those with high incomes (pooled rate ratio for lowest to highest income groups = 1.23; 95% CI 1.05-1.44). There was no strong evidence that disparities in testicular cancer incidence have varied by ethnicity or household income over time. Given the lack of understanding of the etiology of testicular cancer, the unusual patterns identified in the New Zealand context may provide some etiological clues for future novel research.

Risk of testicular cancer according to birthplace and birth cohort in Denmark

Based on the intriguing finding of an east-west gradient of testicular cancer risk in the Nordic countries with a low risk in Finland, intermediate in Sweden, and high risk in Denmark, it was suggested that national practices rather than individual behavior may be important in the etiology of this cancer. We investigated the risk of testicular cancer in all men born in Denmark, 1931-1969 according to birthplace. Testicular cancer information was derived from the Danish Cancer Registry and population data from Statistics Denmark. There was a several fold geographical variation in testicular cancer risk within Denmark. Among men born in the early period, 1931-39, the highest risk was primarily observed in the western part of Denmark whereas no such gradient was observed in more recent cohorts. The incidence of testicular cancer increased in all counties from the earliest to the latest birth cohort, but the increase was highest in the eastern parts of Denmark. The heterogeneity in risk according to place of birth within Denmark suggests that individual behavior plays an important role for the risk of testicular cancer. Based on the Danish data, the factor that may have caused the east-west gradient in testicular cancer risk appears to have been more unevenly distributed in the early part of the past century compared to more recent times.

Testicular cancer incidence trends in the USA (1975-2004): plateau or shifting racial paradigm?

OBJECTIVE

It has been reported that the incidence of testicular cancer has plateaued in some parts of the USA, especially among non-Hispanic Whites in Los Angeles. Temporal trends analysis was conducted over three decades to assess the evidence for such a plateau, and to examine whether the incidence of testicular cancer remains stable across racial/ethnic groups. This study also investigated the influence of age at diagnosis on the incidence of testicular cancer.

STUDY DESIGN

Population-based temporal trends analysis.

METHODS

Using the Surveillance Epidemiology and End Results (SEER), 16,580 newly diagnosed cases of testicular cancer in males aged 15-49 years were identified between 1975 and 2004. Incidence rates were examined by calculating the age-adjusted rates and their 95% confidence interval (CI) for age at diagnosis, SEER areas and race for the year of diagnosis. The percentage change and annual percentage change were examined for trends.

RESULTS

The incidence of testicular cancer is continuing to increase among US males, despite the plateau of the 1990s. Between 1975 and 2004, the age-adjusted incidence rate for males aged 15-49 years increased from 2.9 (1975) to 5.1 (2004) per 100,000. The trends indicated a percentage change of 71.9% and a statistically significant annual percentage change of 1.6% (95%CI 1.3-2.0; P<0.05). Although the incidence of testicular cancer in Blacks remained strikingly low (0.3-1.4 per 100,000), the highest annual percentage change was observed among this group (2.3%, 95%CI 0.8-3.9; P<0.05 for trends). The rates were intermediate among Asians/Pacific Islanders and American Indian and Alaska Natives (0.7-2.9 per 100,000), with a percentage change of 117.3% and a statistically significant annual percentage change of 1.5% (95%CI 0.3-2.7; P<0.05 for trends). The highest rates were reported among Whites (3.2-6.3 per 100,000), with a percentage change of 90.4% and a statistically significant annual percentage change of 2.0% (95%CI 1.6-2.3; P<0.05). The most common age at diagnosis was 30-34 years, while the lowest rates were reported in those aged 15-19 years. Likewise, incidence rates varied by SEER areas, with predominantly White states representing areas associated with the highest reported rates of testicular cancer.

CONCLUSIONS

Overall, the incidence of testicular cancer continues to plateau in the USA, while racial variance persists. Black males demonstrate the greatest increase in annual percentage change. Further studies are needed to examine the recent increase among Black males and the potential determinants.

Clinical and genetic aspects of testicular germ cell tumours

In this paper we review clinical and genetic aspects of testicular germ cell tumours (TGCTs). TGCT is the most common type of malignant disorder in men aged 1540 years. Its incidence has increased sharply in recent years. Fortunately, survival of patients with TGCT has improved enormously, which can chiefly be attributed to the cisplatin-based polychemotherapy that was introduced in the nineteen eighties to treat patients with metastasized TGCT. In addition, new strategies have been developed in the surgical approach to metastasized/non-metastasized TGCT and alterations have been made to the radiotherapy technique and radiation dose for seminoma. Family history of TGCT is among the strongest risk factors for this tumour type. Although this fact and others suggest the existence of genetic predisposition to develop TGCT, no germline mutations conferring high risk of developing TGCT have been identified so far. A small deletion, referred to as gr/gr, identified on the Y chromosome is probably associated with only a modest increase in TGCT risk, and linkage of familial TGCT to the Xq27 region has not been confirmed yet. Whether highly penetrant TGCT-predisposing mutations truly exist or familial clustering of TGCT can be explained by combinations of weak predispositions, shared in utero or postnatal risks factors and coincidental somatic mutations is an intriguing puzzle, still waiting to be solved.

Environmental, occupational and familial risks for testicular cancer: a hospital-based case-control study

Testicular cancer (TC) risk factors remain largely unknown, except for personal history of cryptorchidism and familial history of TC. We conducted a hospital-based case-control study on familial, environmental and occupational conditions in which we compared 229 cases and 800 controls. TC was correlated with cryptorchidism (OR = 3.02; CI: 1.90-4.79), a history of cryptorchidism in relatives (OR = 2.85; CI: 1.70-4.79), and TC (OR = 9.58; CI: 4.01-22.88], prostate cancer (OR = 1.80; CI: 1.08-3.02) and breast cancer (OR = 1.77; CI: 1.20-2.60) in relatives. Living in a rural area or having regular gardening activity (growing fruit or vegetables) was associated with an increased risk of TC (OR = 1.63; CI: 1.16-2.29; OR = 1.84; CI: 1.23-2.75). Regarding occupation, we found a relationship with employment in metal trimming (OR = 1.96; CI: 1.00-3.86), chemical manufacture (OR = 1.88; CI: 1.14-3.10), industrial production of glue (OR = 2.21; CI: 1.15-4.25), and welding (OR = 2.84; CI: 1.51-5.35). In a multivariate model, only a history of cryptorchidism in the men, cryptorchidism in relatives, TC, and breast cancer remained significant. Our findings contribute further evidence to a pattern of TC risk factors, which include the significant weight of personal reproductive history and also of testicular and breast cancer in relatives. By including in a multivariate model variables linked to environmental and occupational exposure and related to familial cancer history, neither living in a rural area nor any occupational exposure appeared to be a potential environmental TC risk factor.

Testicular Cancer Variations in Time and Space in Europe

OBJECTIVES

Testicular cancer (TC) is the most common malignancy in young men. A review of all published articles on TC incidence revealed an increased incidence in Northern and Central Europe. We extended the analysis to the whole of Europe by using all data available, notably from registries.

METHODS

We performed a PubMed search and selected articles dealing with TC incidence. We obtained additional information from data of European registries through the eight volumes of the Cancer Incidence in Five Continents, IARC Scientific Publications.

RESULTS

Since the Second World War, TC incidence has been increasing in nearly all European countries. It has doubled in several countries, including France, since 1970. We observed that the increase followed a gradient: the highest rate is centred in Denmark and Germany, and decreases progressively in a centrifugal manner.

CONCLUSIONS

TC incidence is increasing throughout Europe, but wide discrepancies exist between the different countries. The reasons for such a phenomenon are still unclear although environmental factors are strongly suspected, which could have an impact on male fertility. From a public health perspective, further research using cases collected through national and regional population-based registers and case-control studies must be strongly encouraged.

Re-analysis of the Xq27–Xq28 region suggests a weak association of an X-linked gene with sporadic testicular germ cell tumour without cryptorchidism

BACKGROUND

A testicular germ cell tumour (TGCT) predisposing gene has been mapped to the Xq27 region on the X chromosome. These linkage findings remain to be confirmed by other studies.

METHODS

In 276 patients and 169 unaffected first-degree male relatives, 12 microsatellite markers covering the candidate region were genotyped and used to study possible association of TGCT with Xq27.

RESULTS

In contrast to previously reported linkage of familial TGCT and cryptorchidism with Xq27, we observed an association between the subset of TGCT cases without a family history of TGCT or cryptorchism and marker DXS1193 (p=0.014). Carriers of minor alleles were at increased risk (odds ratio (OR) 4.7, confidence interval (CI) 1.1-19.6)

CONCLUSION

We found an association on Xq27 in a subset of TGCT cases, which suggests the presence of an X-linked gene that slightly or moderately increases risk to develop sporadic TGCT but not cryptorchidism.

A novel 3-bp deletion in the PANK2 gene of Dutch patients with pantothenate kinase-associated neurodegeneration: evidence for a founder effect

Mutation analysis was performed in four apparently unrelated Dutch families with pantothenate kinase-associated neurodegeneration, formerly known as Hallervorden-Spatz syndrome. A novel 3-bp deletion encompassing the nucleotides GAG at positions 1,142 to 1,144 of exon 5 of the PANK2 gene was found in all patients. One patient was compound heterozygous; she also carried a novel nonsense mutation (Ser68Stop). The other patients were homozygous for the 1142_1144delGAG mutation. The 1142_1144delGAG mutation was also found in a German patient of unknown descent. We used polymorphic microsatellite markers flanking the PANK2 gene (spanning a region of approximately 8 cM) for haplotype analyses in all these families. A conserved haplotype of 1.5 cM was found for the 1142_1144delGAG mutation carriers. All the Dutch families originated from the same geographical region within the Netherlands. The results indicate a founder effect and suggest that the 1142_1144delGAG mutation probably originated from one common ancestor. It was estimated that this mutation arose at the beginning of the ninth century, approximately 38 generations ago.

Epidemiology of testicular cancer: An overview

Testicular cancer is a rare disease, accounting for 1.1% of all malignant neoplasms in Canadian males. Despite the low overall incidence of testicular cancer, it is the most common malignancy among young men. The incidence rate of testicular cancer has been increasing since the middle of the 20th century in many western countries. However, the etiology of testicular cancer is not well understood. A search of the peer-reviewed literature was conducted to identify important articles for review and inclusion in this overview of the epidemiology of testicular cancer. Most of the established risk factors are related to early life events, including cryptorchidism, carcinoma in situ and in utero exposure to estrogens. Occupational, lifestyle, socioeconomic and other risk factors have demonstrated mixed associations with testicular cancer. Although there are few established risk factors for testicular cancer, some appear to be related to hormonal balance at various life stages. Lifestyle and occupational exposures occurring later in life may play a role in promoting the disease, although they are not likely involved in cancer initiation. In addition to summarizing the current epidemiologic evidence on risk factors for testicular cancer, we suggest future research directions that may elucidate the etiology of testicular cancer.

Genetic predisposition to testicular germ-cell tumours

Testicular germ-cell tumours (TGCT) are the most common neoplasm in young men. Various studies have suggested the existence of an inherited predisposition to development of these tumours. Genome-wide screens subsequently provided evidence of a TGCT susceptibility gene on chromosome Xq27 (TGCT1) that might also predispose to cryptorchism. However, this putative gene has yet to be identified, and other TGCT susceptibility genes probably exist. Completion of the human gene map and advances in genetic research will facilitate further investigation of genetic predisposition to TGCT. Insight into inheritance of TGCT might lead to the identification of individuals at increased risk of developing the disorder, increase our understanding of the mutation pathways that lead to sporadic cases, and contribute to improvement in diagnosis and treatment. Clinicians should record the family history of cancer and urogenital differentiation defects in patients with TGCT.

Increasing incidence of testicular cancer worldwide: a review

PURPOSE

Testicular cancer (TC) is the most common malignancy in 20 to 34-year-old men. Numerous publications have shown an increase in the incidence of testis cancer in the last 40 years with substantial differences among countries. We evaluated worldwide variations in testicular cancer incidence and compared trends in different regions in the world.

MATERIALS AND METHODS

We reviewed 441 studies provided by a MEDLINE search using the key words testis/testicular, cancer/tumor and incidence that were published between 1980 and 2002. From these articles we selected only those devoted to testis cancer incidence and of them only the most recent studies from each country or region. Nevertheless, articles using the same data base but providing new and additional information, for example differences among ethnic groups or controversial explanations for trends, were also retained. We selected 30 articles and analyzed their methodological approach and main results.

RESULTS

Worldwide we observed a clear trend toward an increased TC incidence in the last 30 years in the majority of industrialized countries in North America, Europe and Oceania. Nevertheless, surprising differences in incidence rates were seen between neighboring countries (Finland 2.5/100,000 cases versus Denmark 9.2/100,000) as well as among regions of the same country (2.8 to 7.9/100,000 according to various regional French registers). In addition, substantial differences in the TC incidence and trends were observed among ethnic groups. The increase in the TC incidence was significantly associated with a birth cohort effect in the United States and in European countries. To date except for cryptorchidism no evident TC risk factor has been clearly demonstrated, although the environmental hypothesis with a key role of endocrine disrupters has been put forward by several groups.

CONCLUSIONS

Such a recent increase in the TC rate in most industrialized countries should lead urologists and andrologists to give more attention to testicular cancer symptoms in adolescents and young adults. In a public health perspective further research using cases collected through national and regional population based registers and case-control studies must be strongly encouraged if we wish to be able to assess future trends in TC incidence rates and also identify risk factors.

Syndromic aspects of testicular carcinoma

BACKGROUND

In patients with hereditary or constitutional chromosomal anomalies, testicular carcinoma can develop sporadically or on the basis of an underlying hereditary genetic defect. Greater knowledge of these genetic defects would provide more insight into the molecular pathways that lead to testicular carcinoma. To the authors' knowledge, little attention has been paid to date to the comorbid occurrence of testicular carcinoma in patients with hereditary disorders or constitutional chromosomal anomalies.

METHODS

The authors performed a review of the literature.

RESULTS

Twenty-five different hereditary disorders or constitutional chromosomal anomalies have been reported in patients who developed seminomatous or nonseminomatous testicular carcinoma.

CONCLUSIONS

Although most of these malignancies were too rare to enable the detection of statistically significant correlations between the chromosomal/hereditary disorder and the testicular tumor, it was striking that many of the patients had also other urogenital abnormalities. Susceptibility to urogenital abnormalities seems to disrupt normal urogenital differentiation and suggests a correlation with testicular dysgenesis and, thus, also with testicular carcinoma. Other evidence of causal involvement has been found in the field of tumor cytogenetics. Some of the genes responsible for hereditary disorders have been mapped to regions that are of interest in the development of sporadic testicular carcinoma. Molecular studies on candidate genes will be required to provide definite answers. Completion of the human gene map and the availability of advanced gene arrays and bioinformatics are expected to greatly facilitate further exploration of the role of hereditary genetic defects in testicular carcinoma.

Testicular carcinoma and HLA Class II genes

BACKGROUND

The association with histocompatibility antigens (HLA), in particular Class II genes (DQB1, DRB1), has recently been suggested to be one of the genetic factors involved in testicular germ cell tumor (TGCT) development. The current study, which uses genotyping of microsatellite markers, was designed to replicate previous associations.

METHODS

In 151 patients, along with controls comprising parents or spouses, the HLA region (particularly Class II) on chromosome 6p21 was genotyped for a set of 15 closely linked microsatellite markers.

RESULTS

In both patients and controls, strong linkage disequilibrium was observed in the genotyped region, indicating that similar haplotypes are likely to be identical by descent. However, association analysis and the transmission disequilibrium test did not show significant results. Haplotype sharing statistics, a haplotype method that derives extra information from phase and single marker tests, did not show differences in haplotype sharing between patients and controls.

CONCLUSION

The current genotyping study did not confirm the previously reported association between HLA Class II genes and TGCT. As the HLA alleles for which associations were reported are also prevalent in the Dutch populations, these associations are likely to be nonexistent or much weaker than previously reported.

Spatial variation and temporal trends of testicular cancer in Great Britain

Increases in testicular cancer incidence have been reported in several countries over a long period. Geographical variability has also been reported in some studies. We have investigated temporal trends and spatial variation of testicular cancer at ages 20-49 in Britain. Temporal trends in testicular cancer incidence were examined, 1974 to 1991 and in mortality, 1981-1997. Spatial variation in incidence was analysed across electoral wards, 1975 to 1991. We used Poisson regression to examine for regional and socio-economic effects and Bayesian mapping techniques to analyse small-area spatial variability. Incidence increased from 6.5 to 11.1 per 100 000 in men at ages 20-34, and from 5.6 to 9.7 per 100 000 in men at ages 35-49, while mortality declined by 50% in both age groups. Risks of testicular cancer varied across regional cancer registries, ranging from 0.79 (95% CI: 0.73-0.84) to 1.32 (95% CI: 1.25-1.38), and was higher in the most affluent compared with the most deprived areas. Analyses within 2 regions (one predominantly urban, the other predominantly rural) did not indicate any localized geographical clustering. The increasing incidence contrasted with a decreasing mortality over time in Great Britain, similar to that found in other countries. The higher risk in more affluent areas is not consistent with findings on social class at the individual level. The absence of any marked geographical variability at small area scale argues against a geographically varying environmental factor operating strongly in the aetiology of testicular cancer.