In which situations do you omit the 5FU bolus in FOLFOX or FOLFIRI?

This is a very commonly asked question in the clinic.

The original studies all included leucovorin (LV) and bolus 5Fu as part of the regimen (FOLFOX, FOLFIRI). However, in the clinic, we know that the 5Fu bolus is the main reason that this patient has significant cytopenia and worse side effects from...

Agree with Dr. @Dr. First Last's detailed response. Historically, the FULV2 biweekly infusion regimens were originated by Dr. Aimery De Gramont in France with 5 FU given over 2 days consecutively as a 400/600 mg/m2 bolus infusion days 1 and 2 every 2 weeks. This was simplified subsequently to bolus ...