Immunohistochemical evidence that P-glycoprotein in non-small cell lung cancers is associated with shorter survival

The expression of P-glycoprotein in 159 non-small cell lung cancers was immunohistochemically examined using a monoclonal antibody (MoAb C219). A total of 93 (60%) cancers were found to be positive for P-glycoprotein. The 5-year survival rates of patients with P-glycoprotein (P-gp+) and those without P-glycoprotein (P-gp-) were 47.6% and 73.6%, respectively (P < 0.05). According to a univariate analysis, P-gp+ was associated with a poor prognosis for males, those with stage I cancer, those who underwent complete resection, and those with adenocarcinoma or squamous cell carcinoma. A multivariate study using the Cox regression analysis indicated that the expression of P-glycoprotein is useful for predicting the prognosis. Among 24 patients who underwent complete resection and postoperative adjuvant chemotherapy, 18 were P-gp+ and the remaining 6 were P-gp-. Of the 18 with P-gp+ cancer, 11 relapsed and 9 died from tumor-related causes, while the other 7 remain free from tumor recurrence; however, all with P-gp- cancer are alive without recurrence. These observations suggest a bias toward a shorter survival for patients with P-gp+ cancer because P-glycoprotein may be associated with chemoresistance. Thus, detection of the expression of P-glycoprotein will aid in planning appropriate adjuvant chemotherapy for patients with non-small cell lung cancer.