Significant calendar period deviations in testicular germ cell tumors indicate that postnatal exposures are etiologically relevant

A Nested Case-Control Study of Serum Per- and Polyfluoroalkyl Substances and Testicular Germ Cell Tumors among U.S. Air Force Servicemen

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are a component of firefighting foams used at military installations. Although high PFAS exposures have been related to cancer risks among civilian populations, the effects for military personnel are unclear.

OBJECTIVES

We investigated associations between serum PFAS concentrations and testicular germ cell tumors (TGCT) among U.S. Air Force servicemen.

METHODS

This nested case-control study involved active-duty Air Force servicemen with sera from the Department of Defense Serum Repository. We selected 530 cases and 530 controls individually matched on birth date, race and ethnicity, year entered the service, and year of sample collection, with prediagnostic serum samples collected between 1988 and 2017. A second prediagnostic sample, collected a median of 4 y after the first, was selected for 187 case-control pairs. Seven PFAS were quantified using isotope-dilution tandem mass spectrometry. Odds ratios (ORs) and 95% confidence intervals (CIs) from conditional logistic regression adjusting for military grade, number of deployments, and, in some models, other PFAS, estimated associations between PFAS concentrations (categorized using quartiles among controls) and TGCT.

RESULTS

Elevated concentrations of some PFAS were observed for military employment in firefighting [perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid] and service at a base with high PFAS concentrations in drinking water (PFHxS). Elevated PFOS concentrations in the second sample were positively associated with TGCT [OR for fourth vs. first quartile ( OR Q 4 ) = 2.6 , 95% CI: 1.1, 6.4; p trend = 0.02 ], including after adjustment for other PFAS (OR Q 4 = 4.6 , 95% CI: 1.4, 15.1; p trend = 0.009 ). Associations with PFOS in the first/only samples were weak and not statistically significant. Elevated concentrations of perfluorononanoic acid were inversely associated with TGCT, whereas results were null for other PFAS.

DISCUSSION

We identified service-related predictors of PFAS concentrations and increased TGCT relative risks with elevated PFOS concentrations among Air Force servicemen. These findings warrant further investigation in other populations and military service branches. https://doi.org/10.1289/EHP12603.

International Trends in the Incidence of Testicular Cancer: Lessons from 35 Years and 41 Countries

BACKGROUND

Incidence rates of testicular cancer (TC) have been increasing in many countries since, at least, the mid-20th century without clear explanation. Examining the varying trends across countries and time provides clues to understanding the causes of TC.

OBJECTIVE

We have presented incidence data from 41 countries and evaluated incidence trends for the 35-yr period from 1978 to 2012.

DESIGN, SETTING, AND PARTICIPANTS

Cancer registry data from Cancer Incidence in Five Continents (CI5) volumes V-XI, CI5plus, and the NORDCAN database were analysed.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Age-standardised rates of TC overall and by histological type were calculated. A joinpoint regression model of the natural log-transformed rates was used to calculate the average annual percent change (AAPC) in incidence. Age-period-cohort modelling was used to examine the effect of birth cohort on rates.

RESULTS AND LIMITATIONS

While the highest incidence of TC remains in Northern Europe, the gap is closing between higher- and lower-incidence regions. Age-period-cohort modelling found flattening of risk among recent cohorts in Denmark and the UK, a steady increase in risk in the USA (particularly for seminomas), and an increase in risk among more recent cohorts in Costa Rica, Croatia, and Slovakia.

CONCLUSIONS

The gap between low- and high-incidence countries is closing due to increases in the former and stabilisation in the latter. Understanding the causes of these and other differences in incidence rates between, and within, countries may help further our understanding of the aetiology of this cancer.

PATIENT SUMMARY

We examined the rates of testicular cancer in different countries over time. These rates have been increasing, although the rates in high-incidence countries seem to be slowing down, while rates in low-incidence countries are catching up. These trends might help us understand what is causing testicular cancer in general.

The puzzling incidence of testicular cancer in New Zealand: what can we learn?

BACKGROUND

Testicular germ cell tumour is the most common cancer to be diagnosed among young men. In New Zealand, we have observed some puzzling trends in the epidemiology of this disease.

METHODS

We have conducted a narrative review of available evidence regarding the puzzling epidemiology of testicular germ cell tumour in New Zealand and discussed the possible drivers of these trends.

RESULTS AND DISCUSSION

Whereas testicular cancer is most commonly a disease of White men, in New Zealand it is the indigenous Māori population that suffer by far the greatest rate of disease (age-adjusted relative risk: 1.80, 95% CI 1.58-2.05). Even more curiously, the rate of testicular germ cell tumour among Māori men aged 15-44 (28/100,000) is substantially greater than for Pacific Island men (9/100,000), a rare example of divergence between these two populations in terms of the incidence of any disease (cancer or otherwise). Our observations beg the following questions: first, why are rates of testicular germ cell tumour so much higher among Māori New Zealanders compared to the already high rates observed among European/Other New Zealanders? Second, why are rates of testicular germ cell tumour so completely divergent between Māori and Pacific New Zealanders, when these two groups typically move in parallel with respect to the incidence of given diseases? Finally, what might we learn about the factors that cause testicular germ cell tumour in general by answering these questions?

CONCLUSION

This review examines the possible drivers of our observed disparity, discusses their feasibility, and highlights new work that is underway to further understand these drivers.

Future of testicular germ cell tumor incidence in the United States: Forecast through 2026

BACKGROUND

Testicular germ cell tumors (TGCTs) are rare tumors in the general population but are the most commonly occurring malignancy among males between ages 15 and 44 years in the United States (US). Although non-Hispanic whites (NHWs) have the highest incidence in the US, rates among Hispanics have increased the most in recent years. To forecast what these incidence rates may be in the future, an analysis of TGCT incidence in the Surveillance, Epidemiology, and End Results program and the National Program of Cancer Registries was conducted.

METHODS

TGCT incidence data among males ages 15 to 59 years for the years 1999 to 2012 were obtained from 39 US cancer registries. Incidence rates through 2026 were forecast using age-period-cohort models stratified by race/ethnicity, histology (seminoma, nonseminoma), and age.

RESULTS

Between 1999 and 2012, TGCT incidence rates, both overall and by histology, were highest among NHWs, followed by Hispanics, Asian/Pacific Islanders, and non-Hispanic blacks. Between 2013 and 2026, rates among Hispanics were forecast to increase annually by 3.96% (95% confidence interval, 3.88%-4.03%), resulting in the highest rate of increase of any racial/ethnic group. By 2026, the highest TGCT rates in the US will be among Hispanics because of increases in both seminomas and nonseminomas. Rates among NHWs will slightly increase, whereas rates among other groups will slightly decrease.

CONCLUSIONS

By 2026, Hispanics will have the highest rate of TGCT of any racial/ethnic group in the US because of the rising incidence among recent birth cohorts. Reasons for the increase in younger Hispanics merit further exploration. Cancer 2017;123:2320-2328. © 2017 American Cancer Society.

Obscure etiology, unusual disparity: the epidemiology of testicular cancer in New Zealand

PURPOSE

Testicular cancer (TC) remains perplexing, both in terms of what causes the disease and why certain populations are at greater risk of developing it. In New Zealand, an unusual ethnic disparity exists, whereby the indigenous Māori population suffer the highest rates of disease. In this study, we further describe the epidemiology of TC in the New Zealand context.

METHODS

Eligible patients diagnosed with TC between 2000 and 2011 (n = 1,800) were determined from the NZ Cancer Registry and linked to mortality data. Census data were used to estimate population incidence of TC and tumor sub-type by ethnic group. Kaplan-Meier and Cox regression analyses were used to compare survival between ethnic groups.

RESULTS

Māori males aged 15-44 were 80% more likely to be diagnosed with TC compared to European/Other males [age-standardized relative risk (RR) 1.80, 95% CI 1.58-2.05]. By contrast, disease burden was comparatively low among Pacific and Asian populations. Māori had a greater incidence of both seminoma (RR 1.88, 95% CI 1.52-2.22) and non-seminoma (RR 1.67, 95% CI 1.35-2.07) germ cell tumors than the European/Other population, reducing the likelihood that our observed disparity is driven by differential propensity to one given sub-type among Māori. Māori had poorer survival outcomes [cancer-specific adjusted hazard ratio (HR) 2.29, 95% CI 1.14-4.59] than the European/Other population.

CONCLUSIONS

Understanding the drivers of New Zealand's unusual incidence disparities--particularly between Māori and Pacific--could further our understanding of the key exposures involved in TC etiology.

A web tool for age-period-cohort analysis of cancer incidence and mortality rates

BACKGROUND

Age-period-cohort (APC) analysis can inform registry-based studies of cancer incidence and mortality, but concerns about statistical identifiability and interpretability, as well as the learning curves of statistical software packages, have limited its uptake.

METHODS

We implemented a panel of easy-to-interpret estimable APC functions and corresponding Wald tests in R code that can be accessed through a user-friendly Web tool.

RESULTS

Input data for the Web tool consist of age-specific numbers of events and person-years over time, in the form of a rate matrix of paired columns. Output functions include model-based estimators of cross-sectional and longitudinal age-specific rates, period and cohort rate ratios that incorporate the overall annual percentage change (net drift), and estimators of the age-specific annual percentage change (local drifts). The Web tool includes built-in examples for teaching and demonstration. User data can be input from a Microsoft Excel worksheet or by uploading a comma-separated-value file. Model outputs can be saved in a variety of formats, including R and Excel.

CONCLUSIONS

APC methodology can now be carried out through a freely available user-friendly Web tool. The tool can be accessed at http://analysistools.nci.nih.gov/apc/.

IMPACT

The Web tool can help cancer surveillance researchers make important discoveries about emerging cancer trends and patterns.