A well-known side-effect of cytostatics (drugs against malignancies) is a decrease in the number of white blood cells, especially of the so-called neutrophil granulocytes, which are very important for the defense against infections. Hence their decrease (called "neutropenia") leads to a predisposition to infections.
Since infections during neutropenia can be very dangerous, the patients are treated with antibiotics from the very first signs of such an infection (usually fever). If the antibiotics (drugs against bacteria) do not lead to a normalization of the body temperature within four days, a drug against fungi is added.
In the IDEA study, one half of the patients receive the antifungal drug voriconazole (as usual) only in case the antibiotics alone do not lead to a normalization of the body temperature (current standard of care). The other half of the patients receive voriconazole immediately after onset of fever (concomitantly with the antibiotics).
The research question is, whether in the "early-treatment" group fewer manifest fungal infections will be observed than in the "late-treatment" group.