[Relationship between the Incidence of Hypomagnesemia and Acneiform Rash and the Therapeutic Effect of Anti-EGFR Monoclonal Antibody in Patients with Metastatic Colorectal Cancer].

PURPOSE: Although anti-EGFR monoclonal antibodies, including cetuximab and panitumumab, are highly effective in KRAS wild-type advanced colorectal cancer, these drugs frequently cause several adverse events. These events include hypomagnesemia and acneiform rash, which may lead to the dose reduction or discontinuation of therapy. In the present study, we retrospectively investigated the incidence of hypomagnesemia and acneiform rash in patients with metastatic colorectal cancer (mCRC). We examined the relationship between the incidence of such adverse events and the therapeutic effect.

METHODS

Thirty-four mCRC patients receiving anti -EGFR monoclonal antibody as a first-line therapy during April 2012 to March 2015 were the subjects of the present study. The symptoms of hypomagnesemia and acneiform rash were graded in accordance with the Common Terminology Criteria for Adverse Events, v4.0.

RESULTS

The incidence rates of hypomagnesemia (all grades) and the acneiform rash (≥grade 2) were 29%and 50%, respectively. Eight patients (24%) exhibited both of these adverse events. The tumor response rate was notable, as it was significantly higher in patients who experienced both of these adverse events compared to those who did not(88% vs 38% for complete response plus partial response, p=0.039). However, the tumor response rate tended to be higher, although not significantly, in patients with either of these adverse events compared to those without it.

CONCLUSION

Concurrent onset of hypomagnesemia and acneiform rash may become a reliable factor capable of predicting the therapeutic effect of anti-EGFR monoclonal antibody.