Panitumumab use in metastatic colorectal cancer and patterns of RAS testing: results from a Europe-wide physician survey and medical records review.

BACKGROUND: In Europe, treatment of metastatic colorectal cancer (mCRC) with panitumumab requires prior confirmation of RAS wild-type mutation status. Two studies - a physician survey and a medical records review (MRR) - were conducted to evaluate the use of panitumumab and awareness among prescribing oncologists of the associated RAS testing requirements in clinical practice.

METHODS: Both studies enrolled participants from nine European countries and were carried out in three consecutive rounds. Rounds 1 and 2 (2012-2013) examined KRAS (exon 2) testing only; the results have been published in full previously. Round 3 (2014-2015) examined full RAS testing (exons 2, 3, 4 of KRAS and NRAS) and was initiated following a change in prescribing guidelines, from requiring KRAS alone to requiring full RAS testing. For the physician survey, telephone interviews were conducted with oncologists who had prescribed panitumumab to patients with mCRC in the previous 6 months. For the MRR, oncologists were asked to provide anonymised clinical information, extracted from their patients' records.

RESULTS: In Round 3, 152 oncologists and 131 patients' records were included in the physician survey and MRR, respectively. In Round 3 of the physician survey, 95.4% (n = 145) of participants correctly identified that panitumumab should only be prescribed in RAS wild-type mCRC compared with 99.0% (n = 298) of 301 participants in Rounds 1 and 2, responding to the same question about KRAS testing. In Round 3 of the MRR, 100% (n = 131) of patients included in the study had confirmed KRAS or RAS wild-type status prior to initiation of panitumumab compared with 97.7% (n = 299) of 306 patients in Rounds 1 and 2 (KRAS only). Of those patients in Round 3, 83.2% (n = 109) had been tested for RAS status and 16.8% (n = 22) had been tested for KRAS status only.

CONCLUSIONS: Physicians' adherence to prescribing guidelines has remained high over time in Europe, despite the change in indication for panitumumab treatment, from KRAS to RAS wild-type mCRC. Additionally, this study demonstrates the uptake of full RAS testing among the majority of oncologists and pathologists.