Interest of pretreatment quantification of anti-cetuximab IgE to prevent severe hypersensitivity reaction to cetuximab.

6028 Background: Hypersensitivity reactions (HSR) are dreaded and relatively frequent adverse events associated with cetuximab (CTX). High pretreatment levels of anti-CTX IgE have been observed in patients (pts) who experienced a grade 3-4 reaction (NCI CTCAE v3.0) after CTX administration. We hypothesized that dosage of anti-CTX IgE prior to treatment in pts naive to CTX may be used for therapeutic decisions to reduce the incidence of severe HSR. Our main objective was to compare the incidence of severe HSR during the first injection of CTX among pts with low levels of anti-CTX IgE, compared to an incidence of 5.2% retrospectively observed among 213 pts previously treated in our centre. Methods: We conducted a multicentre prospective diagnostic trial among pts with a colon or head-and-neck cancer, candidate to a first treatment by CTX. The pre-treatment level of anti-CTX IgE was measured. An IgE level lower than 30 EAU (IgE Arbitrary Unit) did not interfere with the therapeutic decision whereas for pts w...