The aim of this study was to present the incidence and time trends of urinary system cancers in Golestan province between the years 2004–2019. The age-standardized incidence rate of bladder cancer in Golestan is 5.93 per 100,000 which is 9.46 per 100,000 for males and 2.52 per 100,000 for females. According to previous studies, the incidence rate of bladder cancer in Iran in 2022 was 7.1 per 100,000. Nowroozi et al.l study has demonstrated that in Iran, the ASR for bladder cancer is 10.9 per 100,000 in males and 2.8 ASR in female [7]. The ASR for bladder cancer in the world is estimated to be 5.6 per 100,000 in 2022. This rate in Asia is 3.4 per 100,000. Golestan province, with ASR 5.93 per 100,000, has higher incidence rate of bladder cancer compared to Asia and lower rates compared to Iran.
The results of our study showed, the ASR of bladder cancer has increased from 4.97 per 100,000 in 2004 to 7.18 per 100,000 in 2019 and the EAPC of bladder cancer was 1.56%. Although our results didn’t show a significant time trend but it seems that despite the relative increase in the incidence of bladder cancer in the total population of Golestan, and especially in males, bladder cancer shows a decreasing trend in the females − 1.19%. Also the increasing trend in rural areas, is more steep than urban areas. Mousavian et al. showed, the incidence of bladder cancer in Iran has increased from 5.82 to 11.5 between 2005 and 2020. This increase is mostly due to the increase of bladder cancer in males [19],.The results of Norouzi et al. ‘s study in Iran showed that the bladder cancer’s ASR in males has increased from 8.35 to 13.57 between 2003 and 2015 in Iran. The time trends of this cancer in females have been increasing with a slow slope from 2.12 to 2.86 between 2003–2015 [7].
In 2020, the study of Chun Teoh et al. demonstrated that in European countries, the incidence rate of bladder cancer is increasing. Meanwhile, in Asia, the incidence rate of bladder cancer is decreasing [20]. Qiliang Cai and his colleagues in another study state that between 1990 and 2016, the ASR of bladder cancer has decreased from 7.11 to 6.69. This study also has showed the increase in bladder cancer incidence is mainly due to improving life expectancy and population growth in the world [6]. Considering the high incidence rate and increasing trend, this highlights the growing public health concern posed by bladder cancer in the region. In order to better understand and address this issue, it is recommended that further studies be conducted to identify the specific risk factors associated with bladder cancer in this area. Preventative measures and targeted interventions should be implemented to reduce the burden of bladder cancer in Golestan province and improve the overall health outcomes of its residents.
Among the risk factors, smoking tobacco is the greatest risk factor for bladder cancer [21]. Previous studies had showed the joint exposure to cigarette and opium has the greatest impact on these cancers [11, 22, 23]. The prevalence of monthly smoking among Iranian young adults is around 2.7–20%. Considering the high prevalence of smoking in adolescents and young adults, it is expected an increase in the incidence of bladder cancer in younger age groups in near future [24]. These findings confirm that policies to prevent and deal with the use of narcotics and especially cigarettes can play an effective role in health policies related to the control and prevention of bladder cancer.
Contact with items used in aluminum, paint, and rubber industries including aromatic amines, polycyclic aromatic hydrocarbons, and chlorinated hydrocarbons are other important risk factors for bladder cancer [3, 21]. Aromatic amines, or aryl amines are widely used in agriculture [25]. Previous studies have showed that workers in agricultural production of crops and plant farmers have a highly elevated risk for urinary bladder cancer. As agriculture is one of the main occupation in Golestan province, further investigations are warranted to assess the relationship between bladder cancer incidence and exposure to agriculture-related risk factors (e.g. pesticides) among Golestan residence.
In our study males had a higher incidence rate of bladder cancer than females, the incidence rate ratio of female to male (1:4) in bladder cancer demonstrate a significant difference in the incidence rate of bladder cancer between the two sexes. This sex disparity could be related to still high prevalence of smoking and tobacco use in males than females. Also males are more exposed to industrial and occupational chemical agents which can explain these differences [21].
The ASR of bladder cancer was 7.01 and 4.08 per 100,000 in urban and rural areas, respectively. Although our results show higher incidence rate of bladder cancer in urban areas, but previous studies in Golestan province has showed chemical agents like polycyclic aromatic hydrocarbon metabolite concentrations were almost twice as high in rural areas compared to urban areas [26]. Further studies are warranted to clarify this point.
The ASR of Kidney cancer in Golestan province is 2.32 per 100,000 which is 2.75 per 100,000 for males and 1.91 per 100,000 for females. This rate is lower compared to the ASR for kidney cancer in the world (4.4 per 100,000) and higher than Asia (2.6 per 100,000), and similar to the rates reported for Iran (2.3 per 100,000) [27, 28].
Our findings showed increasing trends in incidence rates of kidney cancer in Golestan province from 1.73 in 2004 to 2.44 in 2019, although the trend was not statistically significant. It seems that the trends in incidence rate of kidney cancer in females and rural areas are more steep than males and urban areas. Kidney cancer has faced a global increasing trend in recent years. These increasing time trends are most visible in America and developed European countries. This increase is also evident in Iran’s neighboring countries such as Turkey [27, 28]. The overall increasing trends of kidney cancer could be a result of increasing the prevalence of its risk factors related to urbanization and westernization including increasing prevalence of central obesity and metabolic syndrome. The increasing prevalence of obesity and metabolic syndrome specially in young adults could explain the shifting pattern of kidney cancer to younger age groups as we have also seen in our study [29]. Given the relatively high incidence rates and increasing trend of kidney cancer in Golestan Province, it is recommended that further studies be conducted to identify the factors associated with these changes and preventive methods in the province.
Our results have demonstrated that males (2.09 per 100,000) had a higher incidence rate of kidney cancer compared to females (1.56 per 100,000) in Golestan, which is probably related to the different prevalence of risk factors for kidney cancer among males and females. There are multiple risk factors related to kidney cancer including obesity, smoking, hypertension, Hypercaloric diet, low physical activity and exposure to Chemical Carcinogens like acrylamide, Cadmium, Arsenic and Asbestos [1, 30]. Study of Andreotti et al. has demonstrated significant elevated risks of RCC for agriculture workers in contact with herbisides and insecticides [31]. Smoking, opium use and nass chewing in males and females is highly associated with cancer rates in Golestan province. Alcala et al. has demonstrated that the fraction of cancers that were attributable to smoking cigarettes were higher among males (12%) than females (2%) and among ever opium users (21%) than never opium users (3%) in people diagnosed with cancer in Golestan province [22, 26].
As we discussed earlier hypertension is one of the risk factors for the kidney cancer. The study of Sepanlou et al. results have showed that Golestan province has a high prevalence of hypertension. This study demonstrate that males had lower blood pressure compare to females at all ages and also Turkmen, non-married and illiterate subjects, non-smokers and not opium users also showed higher systolic blood pressure [32]. Also, Previous studies have shown Golestan has a higher incidence of kidney dysfunction compared to other provinces in Iran. In 2019 Golestan has one of the highest age-standardized DALY and age-standardized death rate (ASDR) in Iran for kidney dysfunction disease which can be a risk factor for cancer [33].
Our findings suggested the age-standardized incidence rate of kidney cancer in urban areas (2.71 per 100,000) was higher than in rural dwellers (1.87 per 100,000). Low physical activity and inappropriate Western diet are other risk factors related to kidney cancer which are more common in urban area residents [32]. Zheng et al. in their study has discussed the higher prevalence of RCC in urban areas and its association with increased life expectancy in this population [34]. Golestan province has a higher level of heavy metals concentration in diet and especially in rice which residents consume, including cadmium (Cd), lead (Pb), arsenic and zinc (Zn). Consumption of rice containing high concentrations of these heavy metals could increase the risk of kidney cancer [35]. Further studies are recommended to clarify the associations between these risk factors and the risk of Kidney cancer in our population.
In our study, the highest age-specific incidence of kidney cancer was observed in females in the age range of 75–79 years and in males over 85 years of age. A previous study by Mousaviyan et al. has showed the peak age of kidney cancer in females has decreased over 15 years from 75 + years in 2005 to 74 − 65 in 2020, which has a relatively similar pattern in males [19]. It can be concluded that in the coming years, we will see a decrease in the peak age of kidney cancers in Golestan province, which requires close monitoring and pre-planned health policies.
While this study provides valuable insights into the trends of kidney and bladder cancers in Golestan province, it has certain limitations. The most important limitation is the lack of data on individual risk factors in the GPCR. Because of this, we were not able to assess the role of key contributors such as smoking, opioid use, or other lifestyle-related factors in the development of urinary tract cancers. We also could not examine the possible impact of occupational and environmental exposures, particularly in areas with higher incidence rates. Future studies are suggested to explore how lifestyle, occupational, and environmental risk factors contribute to urinary tract cancers in Golestan. Although some trends were observed in our findings, several of them did not reach statistical significance. This lack of significance introduces a level of uncertainty in interpreting the findings. It is important to consider the potential implications of these results within the context of their limitations, and further research is recommended to better understand the observed patterns.
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