How much can screening reduce colorectal cancer mortality in Japan? Scenario-based estimation by microsimulation

BACKGROUND

Screening is one of the effective interventions for the reduction of colorectal cancer mortality. Though the Japanese government recommends faecal occult blood test and colonoscopy as a follow-up examination following a diagnosis, both participation rates have not been so high and the national mortality rate has not shown a clear decreasing trend.

METHODS

Microsimulation models simulate the life histories of a large population of individuals under various scenarios. In this study, we applied a microsimulation model to estimate the reduction of colorectal cancer mortality based on screening scenarios.

RESULTS

The effect of reducing the age-standardized mortality rate for colorectal cancer was estimated at 9.4% for men and 6.0% for women under the scenario which calls for 50% participation in faecal occult blood test and 90% participation of follow-up examination. This scenario corresponds to the goal setting for screening in the third-term of the Basic Plan to Promote Cancer Control Programs in Japan.

CONCLUSIONS

Our microsimulation model was found to be useful in estimating the mortality reduction effect of cancer control policy. Such modelling techniques can be utilized to develop effective and optimal cancer control programs.

Statistical inference for estimating the incidence of cancer at the prefectural level in Japan

Information of prefectural cancer incidence in Japan is an important resource to plan an effective regional cancer control program. In order to obtain accurate prefectural cancer incidence, we have to adjust for both of completeness of regional cancer registries and regional dispersion, simultaneously, Then, we developed a hierarchal Bayes model with a completeness adjustment by using the relation between MI ratio (mortality divided by incidence) and proportion of death certificate notified among incidence. Prefectural cancer incidence is estimated with the 95% credible interval, which suggests that the national MI ratio should be 0.386 if the registry were complete. Because cancer behavior has a variation depending on prefecture, such accurate incidence must contribute to plan and assess regional cancer control program.

Evaluation of the Japanese Metabolic Syndrome Risk Score (JAMRISC): a newly developed questionnaire used as a screening tool for diagnosing metabolic syndrome and insulin resistance in Japan

Objectives

To prevent the onset of lifestyle-related diseases associated with metabolic syndrome (MetS) in Japan, research into the development of a useful screening method is strongly desired. We developed a new screening questionnaire (JAMRISC) utilizing a logistic regression model and evaluated its ability to predict the development of MetS, type 2 diabetes and other lifestyle-related diseases in Japanese populace.

Methods

JAMRISC questionnaire was sent to 1,850 individuals in Rumoi, a small city in Hokkaido. We received a total of 1,054 valid responses. To maximize the target individuals accurately diagnosed with MetS, logistic regression analysis was used to generate a unique metabolic syndrome score calculation formula as taking into consideration the clinical relevance of each question item as individual coefficients.

Results

The results of our comparative research utilizing both JAMRISC and Finnish Diabetes Risk Score (FINDRISC) questionnaires revealed the usefulness of JAMRISC for its ability to detect risks for MetS, pre-MetS, diabetes, and pre-diabetes. Study of disease risk detection via JAMRISC questionnaire targeting the 4283 residents of Rumoi indicated a high detection rate for pre-MetS (98.8 %), MetS (94.2 %), pre-diabetes (85.1 %) and type 2 diabetes (94.9 %). In addition, JAMRISC was useful not only as a MetS risk score test, but also as a screening tool for diagnosing insulin resistance.

Conclusions

JAMRISC questionnaire is a useful instrument for the detection of early risk of not only MetS and type 2 diabetes but also insulin resistance.

Quantification of the increase in thyroid cancer prevalence in Fukushima after the nuclear disaster in 2011--a potential overdiagnosis?

A thyroid ultrasound examination programme has been conducted in Fukushima Prefecture, Japan, after the nuclear disaster in 2011. Although remarkably high prevalence of thyroid cancer was observed, no relevant quantitative evaluation was conducted. We calculated the observed/expected (O/E) ratio of thyroid cancer prevalence for the residents aged ≤20 years. Observed prevalence was the number of thyroid cancer cases detected by the programme through the end of April 2015. Expected prevalence was calculated as cumulative incidence by a life-table method using the national estimates of thyroid cancer incidence rate in 2001–10 (prior to the disaster) and the population of Fukushima Prefecture. The underlying assumption was that there was neither nuclear accident nor screening intervention. The observed and estimated prevalence of thyroid cancer among residents aged ≤20 years was 160.1 and 5.2, respectively, giving an O/E ratio of 30.8 [95% confidence interval (CI): 26.2, 35.9]. When the recent increasing trend in thyroid cancer was considered, the overall O/E ratio was 22.2 (95% CI: 18.9, 25.9). The cumulative number of thyroid cancer deaths in Fukushima Prefecture, estimated with the same method (annual average in 2009–13), was 0.6 under age 40. Combined with the existing knowledge about radiation effect on thyroid cancer, our descriptive analysis suggests the possibility of overdiagnosis. Evaluation including individual-level analysis is required to further clarify the contribution of underlying factors.

Strength estimation of a moving 125Iodine source during implantation in brachytherapy: application to linked sources

This study sought to demonstrate the feasibility of estimating the source strength during implantation in brachytherapy. The requirement for measuring the strengths of the linked sources was investigated. The utilized sources were (125)I with air kerma strengths of 8.38-8.63 U (μGy m(2) h(-1)). Measurements were performed with a plastic scintillator (80 mm × 50 mm × 20 mm in thickness). For a source-to-source distance of 10.5 mm and at source speeds of up to 200 mm s(-1), a counting time of 10 ms and a detector-to-needle distance of 5 mm were found to be the appropriate measurement conditions. The combined standard uncertainty (CSU) with the coverage factor of 1 (k = 1) was ∼15% when using a grid to decrease the interference by the neighboring sources. Without the grid, the CSU (k = 1) was ∼5%, and an 8% overestimation due to the neighboring sources was found to potentially cause additional uncertainty. In order to improve the accuracy in estimating source strength, it is recommended that the measurment conditions should be optimized by considering the tradeoff between the overestimation due to the neighboring sources and the intensity of the measured value, which influences the random error.

Study of the Effect of Vaccination on Periodic Structures of Measles Epidemics in Japan

The purpose of this paper is to investigate the effect of vaccination on periodic structures of measles epidemics in Japan. We carried out spectral analysis for time series data of measles notifications collected in Japan. It was confirmed that the interepidemic period, which corresponds to the interval between major epidemics of measles, increases as the vaccination ratio increases. This result was supported by a theory based on a mathematical model for epidemics of infectious diseases. It was suggested that the interepidemic period is useful to estimate the effect of vaccination on measles incidences quantitatively.

Short-term projection of cancer incidence in Japan using an age-period interaction model with spline smoothing

OBJECTIVE

In Japan, population-based cancer incidence data are reported several years behind the latest year of cancer mortality data. To bridge this gap, we aimed to determine a short-term projection method for cancer incidence.

METHODS

Data between 1985 and 2007 were obtained from the population-based cancer registries in four prefectures (Miyagi, Yamagata, Fukui and Nagasaki). Three projection models were examined: generalized linear model with age and period (A + P linear); generalized linear model with age, period and their interactions (A*P linear); and generalized additive model with age, period and their interactions smoothed by spline (A*P spline). We performed a 5-year projection for the years 2000 and 2005, based on the data of 1985-95 and 1985-2000, respectively. Seven cancer sites (stomach, liver, colorectal, lung, female breast, cervix uteri and prostate) and all cancers combined were analyzed. The accuracy of projection was evaluated by whether each observed number fell within the 95% confidence interval of the projected number.

RESULTS

The A*P spline model accurately projected 8 of 13 cancer site-sex combinations, whereas the number of site-sex combinations of accurate projection was 2 and 6 for A + P linear and A*P linear models, respectively. For liver and colorectal cancers, the A*P spline model alone performed accurate projections; the relative differences between projected and observed numbers of cancer incidence ranged between -0.4 and +10.9% for the A*P spline, and between +7.4 and +37.6% for the other two models. All three models failed to project sudden increases in prostate cancer between 2000 and 2005.

CONCLUSIONS

The A*P spline model is a candidate method for the projection of cancer incidence in Japan. However, we need a continuous validation for prostate cancer.

Projection of lung cancer mortality in Japan

According to the National Vital Statistics data, age-standardized mortality rates (ASRs) of lung cancer have shown slightly declining trends in Japan for both men and women. In order to evaluate whether this tendency will continue, a Bayesian age-period-cohort (APC) model was applied using the National Vital Statistics data from 1952 to 2001. In the projection, a Gaussian autoregressive prior model was applied to smooth age, period, and cohort effects from its 2 immediate predecessors by extrapolation. Posterior distributions from which we drew inferences on mortality rates were derived from 15,000 iterations using 5000 burn-in iterations. We defined the median of the iterated values as the overall summary mortality rate of the iterated results. Our results suggest that the number of deaths due to lung cancer will double for men and women during the next 3 decades due to the aging of the baby-boomer generation (individuals who were born between 1947 and 1951). Currently declining trends in some age groups will reverse and start to increase again in the next decades. However, for recent birth cohorts, the results of the projection varied according to whether the data set included early age group mortality or not. Lung cancer mortality in the future depends on the risk factors engaged in by today's young people, especially smoking. Strong promotion of anti-smoking measures and careful surveillance for lung cancer are needed.