The present study will include 14 patients who will be followed throughout 3 treatment cycles. Each cycle will be preceded by infusion of mangafodipir or placebo in two groups, each consisting of 7 patients. The primary endpoints will be the most frequent manifestation of FOLFOX6, namely neutropenia and neurosensory toxicity. The secondary endpoints will be the frequency and severity of other FOLFOX6-related adverse events and quality of life.