Bayesian estimates of the incidence of rare cancers in Europe

Invited Commentary: Predicting Incidence Rates of Rare Cancers-Adding Epidemiologic and Spatial Contexts

There are unique challenges to identifying causes of and developing strategies for prevention of rare cancers, driven by the difficulty in estimating incidence, prevalence, and survival due to small case numbers. Using a Poisson modeling approach, Salmerón et al. (Am J Epidemiol. 2022;191(3):487-498) built upon their previous work to estimate incidence rates of rare cancers in Europe using a Bayesian framework, establishing a uniform prior for a measure of variability for country-specific incidence rates. They offer a methodology with potential transferability to other settings with similar cancer surveillance infrastructure. However, the approach does not consider the spatiotemporal correlation of rare cancer case counts and other, potentially more appropriate nonnormal probability distributions. In this commentary, we discuss the implications of future work from cancer epidemiology and spatial epidemiology perspectives. We describe the possibility of developing prediction models tailored to each type of rare cancer; incorporating the spatial heterogeneity in at-risk populations, surveillance coverage, and risk factors in these predictions; and considering a modeling framework with which to address the inherent spatiotemporal components of these data. We note that extension of this methodology to estimate subcountry rates at provincial, state, or smaller geographic levels would be useful but would pose additional statistical challenges.

Estimating Country-Specific Incidence Rates of Rare Cancers: Comparative Performance Analysis of Modeling Approaches Using European Cancer Registry Data

Estimating incidence of rare cancers is challenging for exceptionally rare entities and in small populations. In a previous study, investigators in the Information Network on Rare Cancers (RARECARENet) provided Bayesian estimates of expected numbers of rare cancers and 95% credible intervals for 27 European countries, using data collected by population-based cancer registries. In that study, slightly different results were found by implementing a Poisson model in integrated nested Laplace approximation/WinBUGS platforms. In this study, we assessed the performance of a Poisson modeling approach for estimating rare cancer incidence rates, oscillating around an overall European average and using small-count data in different scenarios/computational platforms. First, we compared the performance of frequentist, empirical Bayes, and Bayesian approaches for providing 95% confidence/credible intervals for the expected rates in each country. Second, we carried out an empirical study using 190 rare cancers to assess different lower/upper bounds of a uniform prior distribution for the standard deviation of the random effects. For obtaining a reliable measure of variability for country-specific incidence rates, our results suggest the suitability of using 1 as the lower bound for that prior distribution and selecting the random-effects model through an averaged indicator derived from 2 Bayesian model selection criteria: the deviance information criterion and the Watanabe-Akaike information criterion.

Descriptive epidemiological study of rare, less common and common cancers in Western Australia

Background

There are no epidemiological studies describing rare cancers in Western Australia (WA). We aimed to fill this gap by estimating the incidence and five-year survival of rare, less common and common cancers in WA, based on definitions for rarity used by the Australian Institute of Health and Welfare and cancer groupings from the project on Surveillance of Rare Cancers in Europe (RARECARE). This research will enable policy- and decision-makers to better understand the size and nature of the public health problem presented by rare cancers in WA. It is anticipated that this study will inform improved health service design and delivery for all WA cancer patients, but particularly those with rare and less common cancers.

Methods

We estimated incidence and five-year survival rates of rare, less common and common cancers in WA using data sourced from the WA Cancer Registry for the 2013–2017 period. Cancers were defined as rare (< 6), less common (6–12), or common (> 12) based on their crude incidence rate per 100,000 people per year.

Results

Rare cancers make up 21.5% of all cancer diagnoses in WA, with a significantly poorer five-year survival of 58.2% (95% confidence interval (CI) 57.3–59.1%), compared to patients diagnosed with a common cancer, whose five-year survival was 87.8% (95% CI 87.3–88.3%). Survival for less common cancers was significantly poorer than both rare and common cancers, at 48.1% (95% CI 47.3–49.0%). Together, rare and less common cancers represent 48.4% of all cancer diagnoses in WA.

Conclusions

While rare cancers are individually scarce, collectively over one in five cancer patients in WA are diagnosed with a rare cancer. These patients experience significantly worse prognoses compared to patients with common cancers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08501-4.

Incidence and Survival of Patients With Conjunctival Melanoma in Europe

Importance

Conjunctival melanoma (CM) is a rare ocular tumor. Estimates of incidence and survival of patients with CM are important to researchers and policy makers.

Objective

To estimate incidence and survival of patients with CM in Europe.

Design, Setting, and Participants

This population-based cohort study used data from 41 European cancer registries adhering to the RARECAREnet project. All individuals diagnosed as having malignant CM from January 1995 to December 2007 coded according to the International Classification of Diseases for Oncology, Third Edition codes C69.0 (conjunctiva) and 8720-8780 (melanoma) were included. Analysis began March 2019.

Main Outcomes and Measures

Trend estimates for incidence and for 5-year relative survival (the ratio of the measured survival of patients to the expected survival in the general population for the same country, age, sex, and calendar year). Crude, age-standardized, and bayesian incidence rates were calculated. Five-year relative survival was calculated by the Ederer II method with the cohort and period approach.

Results

A total of 724 patients 15 years or older (512 [70.7%] were 55 years or older; 366 [50.6%] were female) were analyzed with an overall crude incidence of CM (per 1 000 000 person/y) of 0.46 (95% CI, 0.42-0.49). Crude incidence was similar in men and women (0.48; 95% CI, 0.44-0.54 and 0.46; 95% CI, 0.41-0.51, respectively) and increased with age. Age-standardized incidence increased over time only in men and was the highest in Norway and the Netherlands (more than 0.70). Only 1 case in 14 years was estimated to occur in Iceland vs about 20 cases per year in large countries such as France and Germany. Percentage of 5-year survival (83.5 overall; 95% CI, 78.6-87.3) was not different between adult and elderly patients but showed large geographical disparities across European regions (range, 66-89) and improved markedly in male patients (from 76 in 1995-1998 to 86 in 2003-2007, with a difference of 10.2 [95% CI, 1.3-19.2]; P < .05) becoming similar to that of women in the last period.

Conclusions and Relevance

Although these data are only available through 2007 and based on registries not uniformly covering the European population, the study provides the first Europe-wide estimates of the incidence and relative survival of patients with CM using population-based data. Geographical differences in survival indicate room for outcome improvement in Southern, Northern, and Eastern European countries.

Epidemiology of human papillomavirus-related oropharyngeal cancer in a classically low-burden region of southern Europe

The incidence of human papillomavirus (HPV)-related oropharyngeal cancer is increasing in some regions. Nevertheless, the epidemiology of this disease has not been extensively investigated in southern Europe. We conducted a retrospective cohort study of patients diagnosed with primary oropharyngeal cancer from 1991 to 2016. Cancer tissues underwent histopathological evaluation, DNA quality control, HPV-DNA detection and p16^INK4a immunohistochemistry. Data were collected from medical records. Factors associated with HPV positivity and time trends were evaluated with multivariable Bayesian models. The adjusted prevalence of HPV-related cases in 864 patients with a valid HPV-DNA result was 9.7%, with HPV-DNA/p16^INK4a double positivity being considered. HPV-related oropharyngeal cancer was likely to occur in non-smokers and non-drinkers, to be located in the tonsil or diagnosed at advanced stages. Time-trend analysis showed an increasing risk of HPV-related oropharyngeal cancer in the most recent periods (5-year period increase of 30%). This increase was highest and with a clear increasing trend only in the most recent years (2012–2016). The prevalence of HPV-related oropharyngeal cancer started to sharply increase in the most recent years in our setting, as occurred two decades ago in areas where most oropharyngeal cancer cases are currently HPV-related. Our results provide a comprehensive assessment of the epidemiological landscape of HPV-related oropharyngeal cancer in a region of southern Europe.

Defining and listing very rare cancers of paediatric age: consensus of the Joint Action on Rare Cancers in cooperation with the European Cooperative Study Group for Pediatric Rare Tumors

Although all tumours are rare in childhood, there are some particularly rare paediatric cancers which have not benefited from advances made by the international paediatric oncology network. To establish a shared definition and produce a list of these entities, the European Union Joint Action on Rare Cancers (JARC) promoted a consensus effort. The definition was based on the incidence rates estimated using the information network on rare cancers (RARECAREnet) database, pooling data from 94 population-based cancer registries and 27 countries. The RARECAREnet list of cancers was used to estimate the incidence rates. This list groups cancers by combining the International Classification of Diseases for Oncology, third edition, morphology and topography codes. According to the consensus, very rare paediatric cancers were identified as those with an annual incidence <2/1000000 and corresponded to 11% of all cancers in patients aged 0-14 years. Two subgroups were identified: tumour types typical of childhood (i.e. hepatoblastoma, pleuropulmonary blastoma, pancreatoblastoma) and those typical of adult age (i.e. carcinomas, melanoma). The threshold of 2/1000000 could also be adopted in populations aged 0-19 years: in this case, three tumour types had an incidence rate which was >2/1000000 (i.e. thyroid and testicular cancers and skin melanoma), but the consensus experts considered them as 'very rare' according to their clinical needs (e.g. shortage of knowledge and clinical expertise as the other rare paediatric cancers). The JARC consensus produced a definition and a list of very rare paediatric cancers which may represent a starting point for prioritising research on these tumours, based on data and patients' clinical needs.