Kiura, Katsuyuki

We examined the feasibility of triplet chemotherapy using cisplatin, docetaxel, and irinotecan for patients with recurrent or refractory non-small cell lung cancer (NSCLC), retrospectively. Twenty-five patients (21 men and 4 women) with NSCLC and good performance status who were <70 years old were analyzed. The median age was 58 years. Most patients had performance status 1 (16/25), stage IV disease (18/25) and adenocarcinoma-histology (16/25). Cisplatin and docetaxel were given on day 1 and irinotecan on day 2;the cycle was repeated every 3 weeks. The objective response rate was 39.1% (95% confidence interval:18.7-59.5%). The median survival time and actual 2-, 3-, and 5-year survival rates were 14.3 months, 32%, 20%, and 8%, respectively. Of note, only 6 patients were treated with gefitinib at the recurrence after triplet chemotherapy;of these, 4 (67%) achieved a partial response, which might result in favorable survival. Grade 3/4 toxicities consisted of neutropenia (100%), neutropenic fever (56%), nausea/vomiting (40%), and diarrhea (16%);no cases of treatment-related death occurred. Triplet chemotherapy showed impressive survival data in our clinical trial, but proved too toxic for use in treating patients with NSCLC in the clinical practice.

An etoposide-resistant subline, SBC-3/ETP, from a human small cell lung cancer cell line, SBC-3, was developed by continuous exposure to increasing concentrations of etoposide in culture. The SBC-3/ETP was 52.1-fold more resistant to etoposide than the parent cell line. The SBC-3/ETP was highly cross-resistant to teniposide, adriamycin, vinca alkaloids, 4-hydroperoxycyclophosphamide, CPT-11 and mitomycin C, and marginally cross-resistant to cisplatin, while the subline showed a collateral sensitivity to bleomycin. Topoisomerase I activity in the SBC-3/ETP was reduced to an extent of one half and topoisomerase II activity to an extent of one eighth in comparison with those of the SBC-3. Intracellular accumulation of [3H]-etoposide in the SBC-3/ETP was significantly lower in comparison to the SBC-3. An overexpression of MDR1 mRNA, and the presence of its product, P-glycoprotein, were detected in the SBC-3/ETP by Northern blotting and flowcytometry using a monoclonal antibody of the protein, MRK16. These results indicate that a decreased activity of topoisomerase II is the major factor for the development of etoposide resistance, and that an overexpression of the MDR1 gene is responsible, in part, for the development of resistance to the drug and some structurally unrelated compounds such as adriamycin and vinca alkaloids.