Dianatinasab, A.

Dianatinasab, M.

Khodadost, M.

eprints Iran University of Medical Sciences

Asian Pacific Journal of Cancer Prevention, Vol 19 1155DOI:10.22034/APJCP.2018.19.5.1155 Risk of Penile Cancer among Men Working in Agriculture Asian Pac J Cancer Prev, 19 (5), 1155-1155 Dear EditorWe read with great interest the article authored by Junior et al., (2018) published in APJCP in January 2018. In their study, the authors introduced several risk factors for penile cancer. They suggested that phimosis, smoking, HPV infection and promiscuous sexual behaviour act as risk factors for penile cancer. Although, the findings are interesting, we believe some methodological issues are to be raised to prevent any misinterpretation.Firstly, authors conducted a descriptive (cross-sectional) study to investigate any associations between several factors and the risk of penile cancer among those seeking medical services. However, the study was carried out with no explanation about the defined order of events, i.e. whether exposure occurred before-after or during the onset of the penile cancer (Levin, 2006). This makes the authors conclusion about the causality of the founded associations. This is especially important because long term associations between an exposure and outcome is particularly difficult to establish using such study designs (Höfler, 2005; Rothman and Greenland, 2005).Secondly, in this cross-sectional study, a total of 103 patients with invasive penile cancer who were being treated from 2012 to 2017 were enrolled. In Table 3 of the article, authors reported descriptive statistics (n %) of characteristics of the patients with no comparison group, e.g. healthy individuals. As the result, the authors were not able to report any measures of associations and related p-values. As we know, in measuring associations it is important to compare characteristics of patients with healthy controls (Rothman et al., 2008). In that regard, the title of the present study is not representative of the study design and findings, as no measure of associated risk e.g. relative risk (RR) or odds ratio (OR) was reported for these so-called risk factors (Mann, 2003). The other important concern about the validity of the results (as presented in Table 3) is that there is a significant portion of data missing for many of the study participants and study variables. Any study with such low response rate can be criticized because high missing and non-response rates may cause information and selection biases and misleading results (Mann, 2003). It seems that to reach the desired conclusion, a case-control design would be a preferable approach (Grimes and Schulz, 2002; Mann, 2003; Dianatinasab et al., 2017).The Final issue to be raised with their study is that whether authors enrolled all cases (prevalence LETTER to the EDITORIncreased Risk of Penile Cancer among Men Working in Agriculture: Some Methodological Issuesand incidence cases) or only new cases were included. If all cases were included in the study, the founded associations are potentially based on the survival of the patients and not the occurrence of disease (Szklo et al., 2001). The later issue reminds the crucial importance of prevalence-incidence bias (Freeman and Hutchison, 1980). As conclusion, the previously mentioned methodological issues are to be seriously considered by readers to avoid any misinterpretations of the results and conclusion of the study.Conflict of interestNone.ReferencesDianatinasab M, Fararouei M, Mohammadianpanah M, et al (2017). Hair coloring, stress, and smoking increase the risk of breast cancer: A case-control study. Clin Breast Cancer, 17, 650-9.Freeman J, Hutchison GB (1980). Prevalence, incidence and duration. Am J Epidemiol, 112, 707-23.Grimes DA, Schulz KF (2002). Bias and causal associations in observational research. Lancet, 359, 248-52.Höfler M (2005). The Bradford Hill considerations on causality: a counterfactual perspective. Emerg Themes Epidemiol, 2, 11.Junior PFM, Silva EHV, Moura KL, et al (2018). Increased risk of penile cancer among men working in agriculture. Asian Pac J Cancer Prev, 19, 237-41.Levin KA (2006). Study design III: Cross-sectional studies. Evid Based Dent, 7, 24-5.Mann CJ (2003). Observational research methods. Research design II: cohort, cross sectional, and case-control studies. Emerg Med J, 20, 54-60.Rothman KJ, Greenland S (2005). Causation and causal inference in epidemiology. Am J Public Health, 95, 144-50.Rothman KJ, Greenland S, Lash TL (2008). Modern epidemiology, pp 51-70.Mostafa Dianatinasab1*, Mahmoud Khodadost2, Aria Dianatinasab31Center for Health Related Social and Behavioral Sciences Research, Shahroud University of Medical Sciences, Shahroud, 2Department of Epidemiology, Faculty of Health, Iran University of Medical Sciences, Tehran, 3Department of Biochemistry, Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran. *For Correspondence: dianati.epid@yahoo.comEditorial Process: Submission:01/31/2018   Acceptance:04/14/2018

Increased risk of penile cancer among men working in agriculture: Some methodological issues

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Increased risk of penile cancer among men working in agriculture: Some methodological issues

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