Safety of pemetrexed according to the duration of vitamin B12 and folic acid supplementation prior to the first dose of pemetrexed

OBJECTIVE: Administration of vitamin B12 and folic acid for 7 days prior to the administration of the first dose of pemetrexed is recommended. However, vitamin supplementation rarely is initiated less than 7 days prior to the first dose of pemetrexed. Therefore, we analyzed the safety of pemetrexed with vitamin supplementation for less than 7 days prior to the first dose of pemetrexed. METHODS: Patients were classified into 2 groups according to the duration of vitamin supplementation prior to the first dose of pemetrexed: group A received vitamin supplementation for 7 days or more, and group B received vitamin supplementation for less than 7 days. We analyzed adverse effects, such as myelosuppression, rash, and diarrhea, after 1 cycle of pemetrexed therapy. RESULTS: A total of 70 patients were administered pemetrexed; 40 patients were men and 30 were women with a median age of 64.5 years(range, 43-86 years). A total of 57 patients were classified into group A and 13 into group B; 33 patients were administered pemetrexed as a first-line treatment. Neutropenia of Grade 3 or more was observed in 4/49(8.2%)patients in group A and 2/13(15.4%)patients in group B(p=0.60). There were no significant differences in the rates of occurrence of neutropenia, rash, and diarrhea. CONCLUSION: This retrospective study indicated that patients could be safely treated with pemetrexed if vitamin supplementation is initiated for less than 7 days prior to the first administration of pemetrexed. However, further studies are needed because of a lack of statistical power and adjustment for confounding factors.