Inhibition of carboplatin-induced DNA interstrand cross-link repair by gemcitabine in patients receiving these drugs for platinum-resistant ovarian cancer.

BACKGROUND: The potential of gemcitabine to interact with carboplatin was explored in a phase II trial in platinum-resistant ovarian cancer. Peripheral blood lymphocytes were sampled after drug administration to measure DNA interstrand cross-link formation and repair. PATIENTS AND METHODS: Forty patients received carboplatin target area under concentration-time curve (AUC 4) followed by gemcitabine 1,000 mg/m(2) with a second dose of gemcitabine on day 8. Peripheral blood lymphocytes were obtained in 12 patients before and at intervals during the first cycle of chemotherapy. DNA cross-link formation and repair (unhooking) were measured by the single-cell gel electrophoresis (comet) assay following ex vivo incubation. RESULTS: The global response rate was 47% (Response Evaluation Criteria in Solid Tumors rate, 29%; CA125 rate, 63%). Delays in treatment were seen in 24% of cycles largely due to myelosuppression; 15% of day 8 administration was omitted. Peak carboplatin-induced DNA cross-linking was seen by 24 hours. Significant reduction was seen in the repair of in vivo carboplatin-induced DNA cross-links following administration of gemcitabine. CONCLUSION: An enhanced activity of carboplatin in platinum-resistant ovarian cancer may be due to synergy with gemcitabine through inhibition of repair of DNA cross-links. Future studies should explore coadministration of these drugs, as this may be a more effective schedule.

Early compared with late radiotherapy in combined modality treatment for limited disease small-cell lung cancer: a London Lung Cancer Group multicenter randomized clinical trial and meta-analysis.

PURPOSE: To replicate an earlier National Cancer Institute of Canada (NCIC) trial that examined the effect on survival of the timing of thoracic radiotherapy (TRT) in patients with limited disease small-cell lung cancer (SCLC). PATIENTS AND METHODS: Patients received three cycles of cyclophosphamide, doxorubicin, and vincristine alternating with three cycles of etoposide and cisplatin. Three hundred twenty five chemotherapy- and radiotherapy-naïve patients were randomly assigned to either early TRT administered concurrently in the second cycle or late TRT administered concurrently with the sixth cycle; the dose was 40 Gy in 15 fractions over 3 weeks. RESULTS: TRT was received by 92% and 82% of patients in the early and late arms, respectively (P = .01). Sixty-nine percent of patients in the early arm received all six courses of chemotherapy compared with 80% in the late arm (P = .003). There was no evidence of a survival difference; median overall survival time was 13.7 and 15.1 months in the early and late arms, respectively (P = .23). In a meta-analysis of all eight trials that compared early and late TRT, there were three in which the proportion of patients who completed their planned chemotherapy was similar between the TRT arms (hazard ratio [HR] = 0.73; 95% CI, 0.62 to 0.86) and five in which proportionally fewer patients in the early TRT arm completed their chemotherapy (HR = 1.06; 95% CI, 0.97 to 1.17). CONCLUSION: This study failed to show a survival advantage for early TRT with chemotherapy in limited-stage SCLC, unlike the NCIC trial. However, the results of a meta-analysis suggest that it is essential to ensure that the delivery of chemotherapy is optimal when administered with early TRT.