CHICAGO, June 6 -- Confirming results of previous studies, pemetrexed combined with either cisplatin or carboplatin demonstrated activity in previously untreated malignant pleural mesothelioma, said researchers.
Treatment using a pemetrexed-cisplatin doublet led to an overall response rate of 26.3% in 745 mesothelioma patients, and the combination of pemetrexed and carboplatin was associated with an overall response rate of 21.6%, found Armando Santoro, M.D., of the Instituto Clinico Humanitas in Milan, Italy, along with his colleagues.
One-year survival rate was 63 to 64% using both regimens, Dr. Santoro reported at the meeting of the American Society of Clinical Oncology.
The median time to progression was about seven months with both regimens, said Dr. Santoro. None of the differences was statistically significant.
Somewhat surprising, said Dr. Santoro, was that the carboplatin doublet caused more toxicity, but he feels that pemetrexed-carboplatin remains a better option for elderly patients and other patients with increased susceptibility to chemotherapy's toxicity.
The researchers' findings were derived from an analysis of outcome data on 1,704 chemotherapy-naïve malignant mesothelioma patients, including 1,497 patients with response data. Dr. Santoro indicated they were among more than 3,000 mesothelioma cancer patients worldwide who received pemetrexed alone or in combination with a platinum agent under the pemetrexed expanded access program.
All of the patients had unresectable disease. They received pemetrexed at a dose of 500 mg/m2 by 10-minute intravenous infusion, followed by cisplatin 75 mg/m2 or carboplatin AUC 5. The chemotherapy regimen was repeated every 21 days. Patients treated with pemetrexed-cisplatin were given a median of five cycles of therapy, compared with six cycles for the pemetrexed-carboplatin regimen.
Among the 745 patients, the cisplatin regimen resulted in 15 complete responses (2%) and 181 partial responses (24.3%). Of the 752 patients receiving carboplatin, seven (0.9%) had complete responses and 156 (20.7%) had partial responses, resulting in an overall response rate of 21.6%.
Stable disease was seen in 51.4% of cisplatin-treated patients and 54.1% of patients treated with carboplatin. The disease control rate (CR + PR + SD) was 77.7% with cisplatin versus 75.8% with carboplatin.
Grade 3-4 hematologic toxicity was greater using the pemetrexed-carboplatin doublet, including:
- Neutropenia, 36.1% versus 23.9%
- Leukopenia, 21% versus 13.1%
- Anemia, 14.3% versus 7.2%
- Thrombocytopenia, 14.3% versus 5%
"The important point of this study is that the two combinations demonstrated similar activity," said Dr. Santoro. "As a result, doctors can choose the regimen they consider most appropriate for an individual patient with malignant pleural mesothelioma without having to sacrifice efficacy."Sources
Peggy Peck, Managing Editor, MedPage Today