Kiura, Katsuyuki

Antitumor activities of five platinum analogs, including cisplatin, carboplatin, 254-S, DWA2114R, and NK121, were compared using five human lung cancer cell lines and 19 tumor specimens obtained from lung cancer patients. The antitumor activity was evaluated by determining the ratio of the maximum tolerated dose of each drug to the 70% tumor growth inhibitory concentration in a colony assay. Cisplatin was the most potent agent, followed by 254-S and carboplatin. DWA2114R and NK121 were less potent than cisplatin and 254-S. Cross-resistance to adriamycin was also investigated using an adriamycin-resistant small cell lung cancer subline, SBC -3/ADM30. SBC-3/ADM30 was 1.7- to 4.0-fold more resistant to cisplatin, carboplatin, NK121, and DWA2114R, than was the parent line, SBC-3, and the subline was 2.0-fold more sensitive to 254-S. Using SBC-3, in vitro combination effects of etoposide and cisplatin, carboplatin, or 254-S were evaluated by the median-effect principle. Synergism was noted when cisplatin and etoposide were combined at a fixed molar ratio of 1:1. Combination of carboplatin and etoposide showed an additive effect. The combination of 254-S and etoposide was antagonistic at low concentrations, but was markedly synergistic at higher concentrations. These data suggested the efficacy of 254-S in the treatment of lung cancer.

In an attempt to predict the clinical activity of newly developed anthracycline analogues, ME2303, KRN8602, and SM5887 in the treatment of lung cancer, we compared antitumor activity of these drugs with that of adriamycin, using six human lung cancer cell lines and two drug-resistant human lung cancer sublines. Taking the pharmacokinetic data into consideration, we evaluated the relative antitumor activity: the ratio of area under the concentration-time curve of each drug to the 50% inhibitory concentration of the drug. Regarding this ratio, ME2303 was more potent than adriamycin, SM5887, and KRN8602. Cross-resistance of the new analogues to adriamycin was investigated using an adriamycin-resistant small cell lung cancer subline, SBC-3/ADM100 and an etoposide-resistant subline, SBC-3/ETP. SBC-3/ADM100 being 106-fold more resistant to adriamycin than the parent SBC-3 showed less resistance to the analogues: 1.80-fold to KRN8602, 3.80-fold to SM5887, and 8.60-fold to ME2303. SBC-3/ETP which was 52.1-fold more resistant to etoposide and 39.5-fold more resistant to adriamycin were also less resistant to the new analogues: 3.27-fold to KRN8602, 9.07-fold to SM5887, and 17.3-fold to ME2303. In conclusion, ME2303 was found to be the most potent agent among drugs tested for the treatment of lung cancer, and KRN8602 can be expected to be beneficial for the treatment of drug-resistant small cell lung cancer.

When the development of chemotherapeutic agents reaches the clinical trial stage, it is necessary to perform drug sensitivity tests quickly in order to select the most promising agents for the treatment of cancer. In order to assess the possibility of using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay as a substitute for the human tumor clonogenic assay (HTCA), we evaluated the correlation between the results obtained by these 2 assays in 5 human lung cancer cell lines. The correlation coefficient between the results of the HTCA and the MTT assay was 0.673, indicating a relatively good correlation. The correlation was most prominent in platinum analogues (r = 0.939) and good in anthracyclines/anthracenedione (r = 0.611). However, no significant correlation was observed in vinca alkaloids, etoposide, irinotecan, SN-38 (an active metabolite of irinotecan), and rhizoxin. The results of the MTT assay showed a high degree of correlation with those of the HTCA in predicting the sensitivity of cancer cell lines to platinum analogues, and anthracyclines/anthracenedione. These results suggest that the MTT assay may be more convenient and quickly performed than the HTCA and can replace HTCA in evaluating the effects of anticancer agents, especially the platinum analogues and anthracyclines/anthracenedione.

A pilot study was conducted to assess the efficacy and feasibility of daily low-dose cisplatin with concurrent thoracic irradiation for clinically unresectable non-small-cell lung cancer (NSCLC). Patients with inoperable NSCLC who had poor risk factors such as advanced age, poor performance status, poor lung function, or concomitant active malignancy were entered into the study. Low-dose cisplatin (6 mg/m2) was administered daily before concurrent thoracic irradiation (2 Gy/day; total dose of 60 Gy) was given. Twenty-five patients were registered. The majority of the patients had either stage IIIA (24.0%) or stage IIIB (60.0%) disease. Fifteen patients (60.0%) completed the planned treatment. Both chemotherapy and radiotherapy were stopped in 3 patients (12.0%) due to poor response, and 7 patients (28.0%) partly received radiotherapy alone as a result of their toxicity response. The proportion of total administered dose to planned dose was 90.9% for chemotherapy and 99.3% for radiotherapy, which were comparable to those in previous studies for LA-NSCLC patients without poor risk factors. Grade 3 leukopenia and neutropenia developed in 14 patients (56.0%) and 10 patients (40.0%), respectively, but grade 4 toxicity was not encountered. Grade 3 pneumonitis and esophagitis were observed in 4 patients (16.0%) and 2 patients (8.0%), respectively. The overall response rate was 60.0%. The median survival time was 22 months, and the 2-year survival rate was 50.3%. Daily low-dose cisplatin and concurrent thoracic irradiation were well tolerated even by poor-risk patients with NSCLC, and showed a therapeutic efficacy similar to that for good-risk patients.