Expression of multidrug resistance-associated proteins and their relation to postoperative individualized chemotherapy in gastric cancer

Background: Adjuvant chemotherapy could reduce residual tumor cells and prevent relapse, however, not all patients are suitable for adjuvant chemotherapy. Screening appropriate patients based on molecular markers for individualized adjuvant chemotherapy is necessary. Methods: Between June 2002 and June 2004, 119 patients who underwent radical gastrectomy were retrospectively analyzed. Some patients had adjuvant chemotherapy based on platinum and 5-FU for four to six cycles. Topoisomerase II (ToPo II) negative, multidrug resistance protein (MRP) positive and glutathione S-transferase p (GST-pi) positive were regarded as three risk factors that may be associated with chemotherapy resistance and poor prognosis. Patients were divided into two groups: a high-risk group (>= 2 risk factors) and a low-risk group (<2 risk factors), and tumor recurrence and patient survival time of the two groups were analyzed. Results: The average recurrence time of the low-risk group was significantly longer than that of the high-risk group (21.29 +/- 11.10 versus 15.16 +/- 8.05 months, P <0.01). The 3-year and 5-year survival rates of the high-risk group were 57.4% and 42.6%, however, it had no significant difference compared to 66.2% and 58.5% of the low-risk group (P >0.05). In the high-risk group, the 3-year survival rates of patients with/without chemotherapy were 62.1% and 52.0% and the 5-year survival rates were 44.8% and 40.0%, respectively, but the difference was not statistically significant (P >0.05). In the low-risk group, the 3-year survival rates of patients with/without chemotherapy were 81.2% and 51.5%, and the 5-year survival rates were 71.9% and 45.5%, respectively, these differences were statistically significant (P <0.05). Conclusions: Combined detection of the multidrug resistance (MDR)-related proteins ToPo II, MRP and GST-pi may be prospectively valuable for postoperative individualized chemotherapy and in further predicting the outcomes of gastric cancer patients.