Methods of data analysis

The online analyses mainly assess basic epidemiological indicators: incidence, mortality, prevalence and survival.

The incidence rate reflects the number of newly diagnosed cases in the population of interest over a specific time interval. Incidence can be expressed in different ways. The first way is in absolute numbers, which show the population's total burden of a given disease. The second way is the so-called crude incidence, where absolute numbers are related to 100,000 persons in the population under consideration. Thus, the crude incidence rate takes into account the size of the population under consideration. When the population of interest represents only persons within a specific age range, we speak of an age-specific incidence. Another possible expression is the so-called age-standardised incidence, which considers the size and the age structure of the population of interest. The age-standardised incidence rate represents the theoretical number of cases per 100,000 persons that would be attributable to a given population if the population under study had the same age composition as the selected standard population. For example, the standard population may be a higher regional unit from which the populations being compared are based. Thus, if we compare the incidence in individual regions of the Czech Republic, we can choose the population of the whole Czech Republic as the standard population. In international comparisons, the world or European standard population is most often chosen as the standard population: these represent theoretical populations that approximately correspond to the real world or European population in their ratio of numbers of people in age categories [1-4].

The mortality rate expresses the number of recorded deaths from a given diagnosis (the so-called specific mortality rate) in the population of interest over a specific time interval. Similar to incidence, mortality can be expressed in different ways. We use absolute numbers, crude mortality, age-specific mortality and age-standardised mortality.

The prevalence rate expresses the number of persons alive who currently have the disease or have had it in the past. It is reported as of 31 December of a given year (point prevalence). Prevalence is expressed in absolute numbers or a rate per 100,000 persons of the considered population.

The survival rate of cancer patients is evaluated using overall survival rates and relative survival rates [5]. The so-called relative survival rate is defined as the ratio of the overall survival (representing the total observed mortality in the population of cancer patients) and the so-called expected survival rate (expressing the mortality in the general population, which corresponds to the observed group of patients in terms of age, sex and year of population assessment according to the year of diagnosis). The evaluation is performed from the first detected neoplasm in the diagnosis of interest and only in adults (age at diagnosis 15 years or older). Survival rates are evaluated for all patients with a record in the CNCR (death certificate only [DCO] cases and tumours detected at autopsy were excluded from the calculation) and for the subset of patients in which cancer treatment has been reported. Point estimates of overall and relative survival rates were supplemented with 95% confidence intervals (these show the possible variance of the point estimate of survival with 95% accuracy, given the size of the patient group evaluated). Survival rates are assessed for all patients with a given diagnosis and according to the clinical stage of the disease (if that stage is known). Survival rates were evaluated for 1995–1999, 2000–2004, 2005–2009, 2010–2014, 2015–2019 and 2020–2022. Cases were selected by cohort analysis except for the recent period 2020–2022, where patients were selected by period analysis. Survival rates from all periods were age-standardised for individual diagnoses (and clinical stages where applicable) according to the age structure of patients in the last period, i.e. 2020–2022; the age categories 15-44, 45-54, 55-64, 65-74 and 75+ years were chosen for standardisation. This approach to patient selection makes it possible to provide the most up-to-date survival estimates; one-year, three-year and five-year survival rates were evaluated.

References

  1. SEGI, M, 1960. Cancer mortality for selected sites in 24 countries. Tokohu, University School of Medicine, Japan.
  2. WATERHOUSE, J., C. MUIR, P. CORREA, J. POWELL,1976. Cancer incidence in five continents. Lyon: IARC. 3: 456.
  3. AHMAD, O. B., C. BOSCHI-PINTO, A. D. LOPEZ, C. J. L. MURRAY, R. LOZANO a M. INOUE, 2001. Age standardization of rates: A new WHO standard. GPE Discussion Paper Series. 31, World Health Organization.
  4. PACE, M., E. CAYOTTE, L. AGAFITEI, T. ZUPANIC, B. WOJTYNIAK, M. GISSLER, G. LANZIERI, M. GLICKMAN, E. GRANDE, EUROPEAN COMMISSION and EUROSTAT, 2013. Revision of the European Standard Population: report of Eurostat’s task force: 2013. ISBN 978-92-79-31094-2.
  5. Ederer F, Axtell L M and Cutler S J (1961). The relative survival rate: A statistical methodology. National Cancer Institute Monograph; 6: 101–121.