Medicine/ 3. Healthcare Organization

Professor Igissinov N.S.^1,2,3, Professor Tulebayev R.K. ², PhD students, Zatonskikh V.V.³

¹NGO «Central Asian Cancer Institute», Astana

²The Republican state enterprise on the right of economic management
«Research institute Traumatology and Orthopedics», Astana

³JSC «Astana Medical University», Astana

On the incidence of laryngeal cancer in Kazakhstan

Introduction. The epidemiological studies indicate that the incidence of cancer of the larynx is different in different countries. According to the estimates of the International Agency for Research on Cancer [1] for 2008, in the world, there were about 151 million cases of laryngeal cancer and the morbidity (in both sexes) was 2.2 cases per 100,000 population. Herein, high morbidity rates were registered in developed countries – 4.7⁰/₀₀₀₀, whereas in developing countries rates were 1.7⁰/₀₀₀₀. Studying the features of cancer of the larynx and attempting to find the reasons for the differences in their frequency enhances the knowledge of the etiology and development of prevention to fight this disease.

Purpose of Research: To study the features of the laryngeal cancer incidence among the whole population of the Republic of Kazakhstan.

Research Methods:

The sources of the research were data received from oncologic agencies, on the incidence of laryngeal cancer. This is a retrospective study for the years 1999-2009. Also were used the data from the Agency of Statistics of the Republic of Kazakhstan, on the quantity of the whole population [2]. According to generally accepted methods of biomedical statistics [3, 4], extensive, age-specific, coarse and standardized (world standard) incidence rates of laryngeal cancer were calculated. Also, were determined the annual average values (P), the mean error (m), the 95% confidence interval (95% CI), and the average annual growth/loss (T_g/l in %).

Results:

For the studied period, in total of 4,967 cases of cancer of the larynx were first recorded in Kazakhstan. At that, a high proportion of patients was accrued to the age group ‘60-69’ (36.2%) (Table 1).

Table 1 – Laryngeal cancer in Kazakhstan (1999-2009)

Age groups	Number (%)	Incidence, ^0/0000		Tl, %
		P±m	95% CI
Under 30	19 (0.4)	0.02±0.004	0.015-0.029	−7.9
30-39	86 (1.7)	0.35±0.05	0.25-0.45	−11.4
40-49	550 (11.1)	2.5±0.2	2.0-2.9	−8.2
50-59	1,403 (28.2)	10.1±0.8	8.7-11.6	−3.8
60-69	1,800 (36.2)	17.6±1.1	15.5-19.6	−3.7
70 and older	1,109 (22.3)	15.0±0.9	13.3-16.7	−2.8
Total	4,967 (100.0)	3.0±0.2	2.6-3.3	−3.6

The average age of patients with cancer of the larynx was 61.3±0.2 years (95% CI=61.0-61.7 years). In the dynamics, the patients’ average age indicator increased from 60.6±0.5 years (in 1999) to 62.5±0.5 years (in 2009), and the adjusted average annual growth rate was T_g=+0.3%.

The average annual coarse incidence rate of laryngeal cancer was 3.0±0.2⁰/₀₀₀₀ (95% CI=2.6-3.3⁰/₀₀₀₀). In the dynamics, the coarse incidence rate tended to decrease from 3.8±0.2⁰/₀₀₀₀ (in 1999) to 2.3±0.1⁰/₀₀₀₀ (in 2008) (T_l=−3.6%).

The average annual age-specific incidence rates of cancer of the larynx had a unimodal growth, reaching a peak in the age group ‘60-69’, 15.0±0.9⁰/₀₀₀₀ (Table 1). The incidence in the age group ‘30-39’ was 16 times higher than in the group ‘under 30’. Figures from the group ‘40-49’ were 7 times higher than from the previous group. The morbidity rate in the group ‘50-59 ’was 4 times higher than in the group ‘40-49’ and 2 times less than in the group ‘60-69’. Here at, the differences in age-specific incidence rates of laryngeal cancer were statistically significant (p<0.05). At the same time, the incidence rates of cancer of the larynx in the age groups ‘60-69’ and ‘70 and older’ did not have a statistically significant difference (p>0.05).

Dynamically, the incidence rates of laryngeal cancer tended to decrease in all age groups, with the highest average annual rate of decline being mostly noticeable in the age groups of until 50: ‘until 30’ (T_l=−7.9%); ‘30-39’(T_l=−11.4%); and ‘40-49’ (T_l=−8.2%).

In order to eliminate the possible impact of the population’s age structure on the incidence of cancer of the larynx in Kazakhstan, its elimination from the world standard population was produced. Thus, the standardized rate was 3.1±0.2⁰/₀₀₀₀ (95% CI=2.7-3.5⁰/₀₀₀₀). 95% CIs of coarse and standardized rates superimposed one on another, so the differences were not statistically significant (p>0.05), this means, the age structure of Kazakhstan did not differ from the age structure of the world standard population.

In the dynamics, the standardized (world standard) incidence rates of laryngeal cancer also fell (T_l=−4.8%).

Conclusion

In recent years, the incidence of laryngeal cancer in Kazakhstan has been reducing. The average age of patients with laryngeal cancer had a tendency to "get older" from 60.6 years to 62.5 years. The age-specific rates of cancer of the larynx were greatest at the age of 60-69 years (17.6⁰/₀₀₀₀). In the dynamics, the coarse and age-specific incidence rates of the disease were declining, and the highest trends of decline were observed in the age groups of under 50. The standardized incidence rates of laryngeal cancer were not significantly different from the coarse rates, and, dynamically, these rates were also decreasing.

References:

1. Ferlay J, Shin HR, Bray F, et al (2010). GLOBOCAN 2008 v1.2, Cancer Incidence and Mortality Worldwide: IARC CancerBase No. 10 [Internet]. Lyon, France: International Agency for Research on Cancer; 2010. Available from: http://globocan.iarc.fr, accessed on 24.04.2013.

2. www.stat.kz – official web site of the Agency of Statistics of the Republic of Kazakhstan.

3. Merkov АМ, Polyakov LЕ. Sanitary Statistics. – L., 1974. – 384 p.

4. Stanton Glantz. Biomedical Statistics. – M; 1999. – 460 p.