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

Disparities in Testicular Cancer: A Review of the Literature

Background: Testicular cancer is the most common malignancy diagnosed in adolescents and young adults, and evidence has emerged regarding disparities that affect different groups of patients. Methods: In this article, we conducted a thorough review of this area and summarized the existing literature. Results: Some of the pertinent findings from our review include poorer outcomes for various groups including the native Māori population of New Zealand, those who live in the United States-Mexico border region, those who live in Eastern Europe, those who are uninsured and those with poorer socioeconomic status, amongst others. In the United States specifically, there is significant evidence showing that racial/ethnic minorities, compared to white patients, tend to fare worse with later presentation at higher stages and worse survival rates. Hispanic patients in particular appear to have the potential for more aggressive tumor biology than other groups and are projected to have the highest incidence rates in the US by 2026. Conclusions: Overall, disparities exist in many aspects of testicular cancer and are striking in some instances, and further research is needed in this arena and in potential solutions.

Recent malignant testicular tumor trend in Japan, a country with an aging population: a large-scale study of 2012-2015 hospital-based cancer registry data

OBJECTIVE

Japan's national database of hospital-based cancer registries is estimated to cover ~67% of all new cancer cases. Using this database, we analyzed the characteristics of the recently diagnosed testicular malignancy.

METHODS

We obtained data for 6510 adult testicular malignancy patients diagnosed in 2012-2015. The distributions of patient ages, histological diagnoses and testicular germ cell tumor hospital care volumes were determined.

RESULTS

The most common histology was seminoma (60.3% of all testicular malignancies), followed by non-seminoma (24.1%) and diffuse large B-cell lymphoma (13.1%). The median and mean ages of the testicular germ cell tumor patients were high at 38 and 39.8 years, respectively. The age distribution peaked at 30-40 years, followed by 40-50 years. Approximately 18% of testicular germ cell tumor patients were ≥50 years. The ages of the diffuse large B-cell lymphoma patients peaked at 70-80 years (mean 67.7 years). When the analysis was limited to the testicular germ cell tumor patients who received first-course cancer treatment at the participating hospitals, the number of high-volume hospitals with ≥20 testicular germ cell tumor care volume was limited to 61 (10.0% of the 605 hospitals that treated ≥1 testicular germ cell tumor patient). However, when the patients who changed hospitals during treatment or relapsed after treatment completion were analyzed together, the number of high-volume hospitals increased to 104 (17.0% of 612 hospitals).

CONCLUSION

The testicular germ cell tumor patients' mean age was nearly 40 years. The proportions of older testicular germ cell tumor patients and diffuse large B-cell lymphoma patients were higher than previously thought. The reasons for this trend are unknown, but it is important to address the trend identified herein in a country with a super-aging population.

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.

Testicular Cancer in New Zealand (TCNZ) study: protocol for a national case-control study

Testicular cancer (TC) is by far the most common cancer to affect young men; however, the exposures that cause this disease are still poorly understood. Our own research has shown that Māori men have the highest rates of this disease in New Zealand-a puzzling observation, since internationally TC is most commonly a disease of men of European ancestry. These trends provide us with a unique opportunity: to learn more about the currently unknown exposures that cause TC, and to explain why Māori have the highest rates of this disease in New Zealand. Using epidemiology and genetics, our experienced research team will conduct a nationwide study which aims to answer these internationally important questions.

AIM OF STUDY

The overall aim of the current national case-control study is to identify the key exposures in the development of TC in New Zealand, and explore which factors might explain the difference in the incidence of TC between Māori and non-Māori.

METHODS AND ANALYSIS

Outside of our own investigations into cryptorchidism, we still do not know which exposures are driving the significant incidence disparity between ethnic groups in NZ. The aim of the proposed research is to use a population-based case-control study to identify the key exposures in the development of TC in New Zealand. We will recruit 410 TC cases and 410 controls, and collect (1) environmental exposure data, via interview and (2) genetic information, via genome-wide genotyping.

ETHICS AND DISSEMINATION

Ethical approval for this study was sought and received from the New Zealand Ministry of Health's Health and Disability Ethics Committee (reference # 17/NTA/248). Following a careful data interpretation process, we will disseminate the findings of this study to a wide and varied audience ranging from general academia, community groups and clinical settings, as well as to the participants themselves.

Testicular Germ-Cell Tumours: A Descriptive Analysis of Clinical Characteristics at First Presentation

INTRODUCTION

Clinical characteristics of testicular germ cell tumours (GCTs) apparently change over time, and some vary geographically. The aim of this study is to document the clinical profile of contemporary GCT patients.

PATIENTS AND METHODS

Four hundred twenty-two Caucasian GCT-patients treated in one German centre during 2000-2017, were analysed in terms of patient-age, laterality, histology, tumour-size, clinical stages (CS), pathological (pT)-stages and serum biomarker expression. The results were analysed descriptively and compared with the literature.

RESULTS

Median age was 36 years and 60.2% had seminoma. Βeta-human chorionic gonadotropin was expressed in 37.9% and alpha Fetoprotein in 25.6%. CS1 presenting stage was 66.6% of all GCT patients, 79.1% in seminoma, and 47.6% in nonseminoma. Tumour size was significantly associated with pT-stages and CS. Patients >50 years had significantly more seminoma (77.6%) than younger ones (57.9%). Comparison with literature data revealed a shifting towards higher age, lower CS, higher proportion of seminoma and striking differences of characteristics among geographic regions.

CONCLUSIONS

A typical contemporary clinical profile of testicular GCTs is presented in this study. Median age, relative incidence of seminoma and proportion of CS1 appear to be increasing over time. Striking differences among ethnic groups regarding the characteristics of GCT require further investigation.

Risk factors for cryptorchidism

Undescended testis - known as cryptorchidism - is one of the most common congenital abnormalities observed in boys, and is one of the few known risk factors for testicular cancer. The key factors that contribute to the occurrence of cryptorchidism remain elusive. Testicular descent is thought to occur during two hormonally-controlled phases in fetal development - between 8-15 weeks (the first phase of decent) and 25-35 weeks gestation (the second phase of descent); the failure of a testis to descend permanently is probably caused by disruptions to one or both of these phases, but the causes and mechanisms of such disruptions are still unclear. A broad range of putative risk factors have been evaluated in relation to the development of cryptorchidism but their plausibility is still in question. Consistent evidence of an association with cryptorchidism exists for only a few factors, and in those cases in which evidence seems unequivocal the factor is likely to be a surrogate for the true causal exposure. The relative importance of each risk factor could vary considerably between mother-son pairs depending on an array of genetic, maternal, placental and fetal factors - all of which could vary between regions. Thus, the role of causative factors in aetiology of cryptorchidism requires further research.

Germ Cell Testicular Cancer Incidence, Latitude and Sunlight Associations in the United States and Australia

International patterns suggest germ cell testicular cancer (GCTC) incidence may be lower in lower latitudes. To investigate this possibility, we examined GCTC incidence by latitude (population centroid in 2000) for men ≥15 years within two reasonably homogeneous countries, the United States and Australia. In the United States, we examined age-adjusted incidence/latitude trends using data from states (2001-2010) and local-area registries (1980-2011). In Australia, we evaluated incidence/latitude trends in 61 Statistical Divisions (2000-2009). In U.S. White men (68 566 cases), state incidences increased by latitude, rising 5.74% (4.45-7.05%) per 5°North latitude increment. Similar trends were found for seminoma and nonseminoma subtypes (P < 0.001). In U.S. Black men (2256 cases), the association was also seen (4.9%; 0.2-9.7%). In local U.S. data, similar increases in incidence with latitude were present in each of the last three decades. In Australia (6042 cases), the incidence increased by 4.43% (95% CI: 1.54-7.39%) per 5°South, and trends for subtypes were similar. Thus, we found that incidence of GCTC in both White and Black men increased significantly with distance from the equator, approximately 1% per degree within the range of latitudes studied.

A critical review of methods for assessing cancer survival disparities in indigenous population

PURPOSE

An increasing cancer burden among indigenous populations has led to a growing literature about survival disparities between indigenous and nonindigenous persons. We aim to describe and appraise methods used to measure cancer survival in indigenous persons in the United States, Canada, Australia, and New Zealand.

METHODS

We searched Medline, Web of Science, and EMBASE for articles published between 1990 and 2015 that estimated survival in populations indigenous to one of these four countries. We gathered information about data sources, analytical methods, and the extent to which threats to validity were discussed.

RESULTS

The search retrieved 83 articles. The most common approach to survival analysis was cause-specific survival (n = 49). Thirty-eight articles measured all-cause survival and 11 measured excess mortality attributable to cancer (relative survival). Three sources of information bias common to all studies (ethnic misclassification, incomplete case ascertainment, and incomplete death ascertainment) were acknowledged in a minority of articles.

CONCLUSIONS

The methodological considerations we present here are shared with studies of cancer survival across other subpopulations. We urge future researchers on this and related topics to clearly describe their data sources, to justify analytic choices, and to fully discuss the potential impact of those choices on the results and interpretation.

Ethnic patterns of hypospadias in New Zealand do not resemble those observed for cryptorchidism and testicular cancer: evidence of differential aetiology?

It has been proposed that hypospadias, cryptorchidism, poor semen quality and testicular cancer might share common prenatal causes. We have previously demonstrated similar ethnic patterns for the incidence of testicular cancer and cryptorchidism - a known risk factor for testicular cancer. If the underlying exposure(s) that cause hypospadias, cryptorchidism and testicular cancer are shared, then we would expect the incidence relationship between ethnic groups to follow the same pattern across all three conditions. We followed a birth cohort of 318 345 eligible male neonates born in New Zealand between 2000-2010, and linked routinely collected maternity records with inpatient hospitalization and mortality records through to 2011. We searched hospitalization records for diagnoses of hypospadias, and used mortality records for censoring. We used Poisson regression methods to compare the relative risk of hypospadias between ethnic groups, adjusting for perinatal risk factors and total person time. We observed that European/Other children had the highest risk of hypospadias, with Māori, Pacific and Asian boys having around 40% lower risk of disease compared with this group (adjusted relative risk [RR]: Māori 0.62, 95% CI 0.55-0.70; Pacific 0.62, 95% CI 0.53-0.72; Asian 0.57, 95% CI 0.47-0.69). This contrasts substantially with our previous observations for cryptorchidism and testicular cancer, where Māori males have the greatest risk. Our observations suggest that - at least in New Zealand - the exposures that drive the development of hypospadias may differ to those that that drive the development of cryptorchidism and/or testicular cancer.