Socioeconomic Inequality in Colorectal Cancer Stage at Diagnosis Time in Qazvin City during 2014-2016: Concentration Curve Approach

Abstract

Background: The impact of socioeconomic status on cancer survival has already been proven. Early diagnosis of cancer is one of the main reason of this improved survival among high socioeconomic status (SES) people. High SES people are more likely to take part in cancer screening programs for several reason and it seems that diagnosis of cancer is earlier among these people. Despite growing evidence on inequal in cancer survival, diagnosis, and treatment over the past decades there is a lack of evidence on volume and direction of socioeconomic inequality regarding early diagnosis of cancer in Iran. Objectives: To assess socioeconomic inequality in colorectal cancer stage at diagnosis time in Qazvin city, Iran during 2014 - 2016. Methods: A cross-sectional study was conducted on 200 patients who were diagnosed with colorectal cancer (CRC) at the Vellayat hospital of the Qazvin city. The Principal Component Analysis (PCA) approach was used to combine household assets as a proxy of SES. Cancer staging information was extracted from the patient's medical records and then a pathology specialist performed cancer staging. Descriptive statistics and a multiple logistic regression model were used to illustrate an association between CRC late diagnosis and socioeconomic status adjusted for age, sex, and residence of the area. We applied the standardized Concentration Index as a measure of socioeconomic inequality in CRC late diagnosis. Results: The overall percentage of late CRC diagnosis was 40.5% (95% confidence interval (CI) 33.8, 47.5), which was slightly higher among women (47.1%, 95% CI 36.8, 57.6) than men (35.4%, 95% CI, 27.0, 44.7). Logistic regression results spotted an association between SES and the late diagnosis of CRC. In Iranian women, CRC tended to be diagnosed at more advanced stages among the third (Odds Ratio (OR) = 7.68), forth (Low) (OR = 17.86) and fifth (Lowest) (OR = 25.60) SES quintiles, while in men it was only significant for the fifth quintiles (OR = 4.17). Furthermore, the concentration index implied that late CRC diagnosis is concentrated among deprived subgroups in Qazvin city, and it was statistically significant (Overall concentration index = -0.33, 95% CI -0.38, -0.28). It was estimated at -0.35 and -0.29 in Iranian women and men, respectively. Conclusions: According to this survey, CRC tends to be diagnosed at more advanced stages among low socioeconomic status groups, and the observed discrimination is more severe in Iranian women.