Background: The incidence and mortality rates of prostate cancer are expected to increase in the next two decades in southern Thailand. In addition, survival rates are lower compared to more developed countries such as the US. Differences in the incidence of prostate and other cancers have been observed among the two most predominant religious groups in Thailand, Buddhists and Muslims, possibly due to different dietary and cultural practices between them. However, to our knowledge, no studies have examined differences in cancer survival in these two populations. Thus, we examined differences in tumor characteristics at diagnosis and survival in Buddhist and Muslim men with prostate cancer in southern Thailand.
Methods: Songkhla, Thailand is a southern province located on the eastern side of the Malaysian Peninsula with a relatively large Muslim population (25%). 855 incident prostate cancer cases from the population-based Songkhla cancer registry were included in this study. Data collected by the registry include age at diagnosis, tumor stage and grade, and vital status. Complete data were available from 1990-2013. Age at diagnosis and tumor characteristics were compared across religious groups using the Wilcoxon test for age and the X2 test for categorical variables. Median survival time and 5- year survival rates were calculated using the Kaplan Meier method, and differences by religious group were evaluated using the log-rank test. Cox proportional hazards models were used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for mortality after adjustment for age at diagnosis, stage, and grade.
Results: Of the 855 prostate cancer cases, 89.6% were Buddhists and the rest Muslims. Age, stage, and grade at diagnosis were all similar across religious groups (p=0.72, 0.33, and 0.46 respectively). The median survival time after diagnosis of prostate cancer was significantly longer (p=0.05) in Buddhists 3.7 years (95%CI: 3.2, 4.2) compared to Muslims 2.8 years (95%CI: 1.7, 4.0). The probability of surviving after five years was 39.6% (95%CI: 35.7%, 43.4%) and 31.8% (95%CI: 21.1%, 42.9%) in Buddhists and Muslims, respectively. After adjustment for age at diagnosis, Muslim men were more likely to die after diagnosis with prostate cancer than Buddhist men (HR: 1.37, 95% CI: 1.04, 1.79). This finding was unchanged after further adjustment for stage and grade at diagnosis (HR: 1.31, 95% CI: 1.00, 1.72).
Conclusions: Muslims in Songkhla, Thailand had a higher risk of death after diagnosis of prostate cancer vs. Buddhists. This association could not be explained by differences in tumor characteristics at diagnosis. Understanding what risk factors may underlie the poorer survival observed among Muslims may inform targeted interventions for prostate cancer among the Muslim population in southern Thailand. Next steps include examining this association in additional geographic areas across Thailand.
Citation Format: Christian Alvarez, Laura Rozek, Hutcha Sriplung, Alison M. Mondul. Differences in prostate tumor characteristics and survival among religious groups in southern Thailand [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3272. doi:10.1158/1538-7445.AM2017-3272