Comparison between Parametric and Semi-parametric Cox Models in Modeling Transition Rates with Gastric Cancer

Gastric cancer is one of the most common causes of cancer deaths all over the world. Every year, more than 870 thousand new cases are reported throughout the world and more than 650 thousand people die from this type of cancer (Parkin, 1998). According to the latest statistics of Iran Cancer Research Center, gastric cancer is the most common cancer among Iranian men and the third most common cancer among Iranian women after breast cancer (Mohagheghi et al., 1998; Mohagheghi, 2004). One of the most important objectives specified after the right diagnosis and prompt treatment for the patients with gastric cancer is the survival rate increase especially the 5-year survival rate. Unfortunately, more than 80% of patients with gastric cancer are diagnosed at a stage when common treatments such as gastrectomy, chemotherapy, or radiation therapy are not effective in increasing the patients’ survival (Gunderson and Sosin, 1982; Wisbeck et al., 1986; Sadighi et al., 2005; Samadi et al., 2007; Sadighi