High vs. low-dose leucovorin in regimens with fluorouracil in colorectal cancer therapy.

The problem of unavailability of drugs and shortages have been a common problem in recent years. Shortages may threaten some treatment regimens for oncological patients. This article presents a systematic review of studies evaluating the efficacy and safety of chemotherapy regimens combining fluorouracil and standard or low-dose leucovorin in treating colorectal cancer. A total of 13 prospective and retrospective studies were included in the review. Meta-analyses and review papers were excluded. It is apparent from the systematic review that a lower dose of leucovorin does not fundamentally affect the efficacy of regimens combining 5-fluorouracil with leucovorin in treating patients with colorectal cancer. Similarly, even in the case of safety, reducing the dose of leucovorin did not influence the frequency and severity of observed adverse effects. Surprisingly, in three studies, some of the adverse effects occurred more often with the higher dose of leucovorin. Furthermore, the article presents the results of a questionnaire survey of the management of leucovorin shortages at the departments of preparation of cytostatics (N = 46) within the Czech Republic. In total, 35 workplaces provided feedback. In 17 cases, the departments for the preparation of cytostatics in the Czech Republic had to accept restrictions on administering the full dose of leucovorin. These restrictions consisted of reducing the dose of the injectable form of leucovorin, changing the chemotherapy regimen, administering the oral form of calcium folinate, forcing a therapeutic break, or a combination of these approaches.