Background: To investigate the relationship between multidrug resistance(MDR) and chemotherapy and the possibility of P-gp as a clinical prognostic indicator.
Methods: P-gp, MDR1 gene product, was detected in 66 cases of relapsed lung cancer patients after chemotherapy and 131 lung cancer patients with no prior chemotherapy by immunohistochemistry.
Results: The expressive level of P-gp in relapsed group after chemotherapy was much higher than that of non-chemotherapy group (P<0.05). A significant difference of P-gp expression existed between before and after chemotherapy for squamous cell carcinoma and SCLC (P<0.05), but not for adenocarcinoma. In non-chemotherapy group, lung cancer tissues with different histological types had different P-gp positive rates, which were adenocarcinoma, squamous cell carcinoma and SCLC in sequence from high to low (P<0.05). In relapsed group after chemotherapy, there was no significant difference among the three types of lung cancer (P>0.05). P-gp positive group had a significantly lower 3-year survival rate than negative group (P<0.05).
Conclusions: Chemotherapy may increase the incident rate of MDR in lung cancer. Adenocarcinoma is mainly primary MDR while SCLC and squamous cell carcinoma are mainly secondary to chemotherapy. P-gp expressive level can be used as a common clinical indicator for prognosis and chemotherapy in the patients with lung cancer.