Underestimation of cancer incidence in Iran and necessity for establishing population-based cancer registries

With the great interest we read the paper recently reported incidence and trend of common cancers in I.R of Iran in 2004–2008 (Amori, Aghajani, Asgarian, & Jazayeri, 2016). The authors estimated that age-standardised incidence rates (ASR) of all sites of cancer 87.81 per 100,000 among women and 71.95 per 100,000 in men in I.R of Iran (Amori et al., 2016). In this letter, we would like to draw your attentions to the defect of the Iranian cancer registry that has led to substantial underestimations in the incidence rates of cancer in I.R of Iran. We advocate necessities for establishment of population-based cancer registries to provide valid and reliable cancer statistics in I.R of Iran, which will face cancer epidemics in the near future as other low- and middle-income countries. Iran has established a national programme for pathology-based cancer registry since 1984 and reported cancer incidence for 30 provinces up to 2009 (Zendehdel, Sedighi, Hassanloo, & Nahvijou, 2011). However, previous studies evaluated quality of this programme and demonstrated that the reported results are underestimated and the true incidence is higher than the reports from pathology-based cancer registry (Khodadost et al., 2015; Zendehdel et al., 2011). The reason for this underestimation is simply because pathology-based cancer registry collect part of cancer data from the reference population as it only collects the data from patients who were biopsied or operated. As other low- and middle-income countries, cancer patients are usually diagnosed in advance stages and clinicians may use palliative care instead of referring them to the surgery. Therefore, these patients will not be captured by pathology-based registry. In addition, several patients lack access to the operation and pathology departments for microscopic verification. The other reason is that this programme does not cover all the pathology centres in the country and some pathology centres did not send their data to the registry programme (Zendehdel et al., 2010). We recently performed a validation study in Tehran and found that 30% of the cases were not reported to the cancer registry office in 2008 (Zendehdel K, unpublished), indicating that even the data from pathology laboratories are inadequate. Given the above criticism, we believe that pathology-based cancer registry should not be the base for estimation of the cancer incidence at the population level. The age-standardised incidence rates (ASR) reported in this paper were lower than the rates reported by Golobocan 2012, where the ASR of cancers in overall (excluding non-melanoma skin cancer) was 134.7 and 120.1 per 100,000 in male and female respectively (Forman et al., 2014). The corresponding estimates were 165.3 and 134.3 per 100,000 in male and female, respectively, in Golestan province population-based cancer registry (GCR), the most reliable estimates from Iran, which was published in the Cancer in Five Continents X in 2013 (Roshandel et al., 2012). In addition, a decade ago in 1998–2001, ASRs were 141 per 100,000 for women and 163 per 100,000 for men in the population-based cancer registry of the capital city of Tehran (Mohagheghi, Mosavi-Jarrahi, Malekzadeh, & Parkin, 2009), in which more than 10% of Iran population live and could be seen as cross-representative of the Iran population (Figure 1). Therefore, we believe that the true rate of cancer incidence in whole country is higher than 150 per 100,000 indicating that the estimates provided in this paper were 50% of the true rates. Likewise the reported trends could be due to the improvement of the registration activities in the country and should be interpreted cautiously. In conclusion, the time trends and incidence rates of cancer in Iran that were reported by Amori et al. is considerably lower than true rates and authors have provide a biased estimates in this paper. Additional data from hospitals, clinics, causes of death registry and establishment of the population-based cancer registry are crucial for proper estimation of incidence rates for cancer in Iran and many other low- and middle-income countries.