Showing papers by "Freddie Bray published in 2006"

Predicting the future burden of cancer.

Abstract: As observations in the past do not necessarily hold into the future, predicting future cancer occurrence is fraught with uncertainty. Nevertheless, predictions can aid health planners in allocating resources and allow scientists to explore the consequence of interventions aimed at reducing the impact of cancer. Simple statistical models have been refined over the past few decades and often provide reasonable predictions when applied to recent trends. Intrinsic to their interpretation, however, is an understanding of the forces that drive time trends. We explain how and why cancer predictions are made, with examples to illustrate the concepts in practice.

Trends in testicular cancer incidence and mortality in 22 European countries: continuing increases in incidence and declines in mortality

Abstract: This study profiles testicular cancer incidence and mortality across Europe, and the effects of age, period and generational influences, using age-period-cohort modeling. Despite a 5-fold variation in incidence rates, there were consistent mean increases in incidence in each of the 12 European countries studied, ranging from around 6% per annum (Spain and Slovenia) to 1-2% (Norway). In contrast, declines in testicular cancer mortality of 3-6% per annum were observed in the 1980s and 1990s for the majority of the 22 countries studied, particularly in Northern and Western Europe. The mortality trends in several European countries were rather stable (Romania and Bulgaria) or increasing (Portugal and Croatia). Short-term attenuations in increasing cohort-specific risk of incidence were indicated among men born between 1940 and 1945 in 7 European countries. In Switzerland, successive generations born from the mid 1960s may have experienced a steadily declining risk of disease occurrence. While the underlying risk factors responsible remain elusive, the temporal and geographical variability in incidence may point to an epidemic in different phases in different countries-the result of country-specific differences in the prevalence of one or several ubiquitous and highly prevalent environmental determinants of the disease. Advances in treatment have led to major declines in mortality in many European countries from the mid 1970s, which has translated to cohorts of men at successively lower risk of death from the disease. Slower progress in the delivery of optimal care is however evident from the mortality trends in several lower-resource countries in Southern and Eastern Europe. The first beneficiaries of therapy in these populations may be those men born--rather than diagnosed--in the era of major breakthrough in testicular cancer care.

Interpreting the international trends in testicular seminoma and nonseminoma incidence.

Abstract: There are considerable geographic, ethnic and temporal variations in the global incidence of testicular cancer. The disease mainly affects Western populations, with average rates in developed areas of the world six times higher than those in developing areas. About 500,000 new cases were diagnosed worldwide in 2002, with the vast majority being germ cell tumors and occurring in young adult males. Traditionally, these tumors are further classified into seminoma and nonseminoma. In this Review, trends in the incidence of germ cell tumors are examined using high-quality cancer-registry data from 41 populations within 14 countries worldwide. To assess whether trends of seminoma and nonseminoma incidence are similar, data were analyzed by birth cohort. These analyses should reveal similar trends if the 10-year difference in the clinical manifestation of cancer between subtypes is caused by differences in the speed of progression from the same early rate-limiting step to the onset of symptomatic disease. In each country, incidence has uniformly increased in successive generations born from around 1920 until very recently. Cohort-specific trends in seminoma incidence are similar to cohort-specific trends in nonseminoma incidence, lending support to the conclusion that the subtypes are epidemiologically and etiologically comparable. The findings presented are related to current theories and evidence regarding the determinants of testicular germ cell cancer.

Do Testicular Seminoma and Nonseminoma Share the Same Etiology? Evidence from an Age-Period-Cohort Analysis of Incidence Trends in Eight European Countries

Abstract: The incidence of the two main clinical subentities of testicular germ cell cancer (seminoma and nonseminoma) is increasing throughout Europe. Most studies have revealed little variation in risk factors between the two subtypes. This study compared generation-specific trends in eight European countries, hypothesizing that similar temporal pattern by birth cohort implied that seminoma and nonseminoma had a largely comparable etiology. The results are presented using the age-period-cohort model and the nonidentifiability problem highlighted by partitioning the age, period, and cohort effects in terms of their linear and curvature component parts, assuming a priori that cohort effects predominated. Despite uniform overall increases by calendar period, declining rates of nonseminoma but not pure seminoma were observed in the majority of countries during the 1990s. The subtype trends were, however, largely analogous on a birth cohort scale. Notable observations were a decline in rates of both subtypes among recent birth cohorts in Switzerland and a short-term wartime effect in several countries, involving an attenuation of increasing risk of both subtypes in men born in 1940 to 1945. Departures from the steady increases in testicular cancer over time were likely to occur for nonseminomas some years ahead of seminoma on a period scale. The importance of birth cohort coincided with the view that given a short time interval of susceptibility to exposures earlier in life and a biologically constant time to diagnosis, all temporal changes in rate-limiting exposures should appear as generational effects. Trends in seminoma and nonseminoma conform to largely the same temporal patterns on this scale, implying that they share important etiologic factors.

Temporal studies of cancer occurrence and applications of the age-period-cohort method to trends in Europe

Abstract: This thesis examines the utility of temporal studies of cancer in practice, particularly from the perspective of analyses of the three underlying time components, age, period of event and birth cohort. This enquiry encompasses a review of temporal studies and routine data sources, as well as a more critical appraisal of the strategies available for APC analysis and presentation. Specific methods are then applied to trends in cancer incidence and mortality in Europe. The central aims of the thesis are: 1) to comprehensively review the graphical and analytical approaches available, particularly in relation to APC modelling and their usage in current practice; 2) on the basis of 1), to provide broad but sensible guidelines for the analyses of time trends; 3) on the basis of 2), to practically demonstrate the utility of time trends and the APC model; 4) to consider the benefits and limitations of systematic approaches applied to time trend studies. The recommended strategies are used as guiding principles for a detailed analysis of trends in incidence and mortality rates of three cancers (cervix, endometrium and testis) in European populations. The analyses of these neoplasms - purposely selected given their differing temporal and aetiological profile as well as their means of prevention - provides a platform to demonstrate the utility of APC analyses and the specified recommendations in practice. This motivates a discussion of the difficulties inherent in such studies and the consequences of introducing systematic approaches to the analyses of cancer trends.

Etiologic Conclusions from Similar Birth Cohort Effects

Abstract: In Response: We thank Drs. Stang and Jockel for their comments ([1][1]) on our article ([2][2]). In our study, we compared the incidence rates of testicular seminoma and nonseminoma in adult men using data from high-quality population-based registries across Europe, hypothesizing that a consistent