Discordancy in BRAF mutations among primary and metastatic melanoma lesions: clinical implications for targeted therapy.

Systemic targeted molecular therapy, in the form of a selective BRAF inhibitor with or without a MEK inhibitor, is a standard treatment for patients with BRAF V600 mutation-positive melanoma with unresectable stage III and IV disease. Patients with BRAF mutation-negative primary tumors may manifest BRAF mutation-positive metastatic disease. It is unclear whether all metastatic lesions carry the same BRAF mutation status found in the primary tumor and if discordancy exists, in what frequency it occurs. Primary and matched metastatic lesions in 25 melanoma patients were tested for the BRAF V600E/Ec, V600K, V600D, and V600R mutations using a BRAF RGQ PCR kit (Qiagen). Four patients (16%) had discrepancies between their primary and metastatic melanoma BRAF status. Of these patients, 2 (8%) had BRAF mutation-positive primary melanomas with BRAF mutation-negative metastatic lesions and 2 (8%) patient had BRAF mutation-negative melanoma with a BRAF mutation-positive metastatic lesion. In summary, discordancy of BRAF mutation status is not an infrequent finding between primary and metastatic melanoma. It may be prudent in previously negative patients to determine BRAF mutation status of new metastatic tumors for proper allocation of BRAF inhibitor therapy. Discordant BRAF status may have a role in the varying patterns of response and inevitable resistance seen with BRAF inhibitor therapies.

Performance evaluation comparison of 3 commercially available PCR-based KRAS mutation testing platforms.

The identification of KRAS mutations in patients with certain types of cancer, including colonic adenocarcinoma and non-small cell lung carcinoma, has become increasingly important as these patients are contraindicated from receiving epidermal growth factor receptor-targeted therapies. Several polymerase chain reaction (PCR)-based tests are commercially available for KRAS mutation testing including Applied Biosystems KRAS Mutation Analysis on the ABI3130xl, Qiagen therascreen KRAS RGQ PCR on the Rotor-Gene Q MDx, and Qiagen KRAS Pyro on the PyroMark Q24; however, these tests have not been compared side by side. The purpose of this study was to evaluate the performance characteristics and workflow for 3 PCR-based methods of detecting KRAS mutation status. We evaluated the performance characteristics and workflow for 3 commercially available KRAS mutation detection platforms. All of the 188 samples run were successful, with 29% being positive for the KRAS mutation. Of the positive tests, Applied Biosystems detected 84% of the positive cases, whereas Qiagen therascreen RGQ and Qiagen KRAS Pyro detected 100% of the positive cases. In cases of discrepancy between Applied Biosystems and therascreen RGQ, Pyro agreed with therascreen RGQ 95% of the time. Qiagen therascreen RGQ and Pyro were comparable in terms of sensitivity, specificity, positive predictive value, negative predictive value, and accuracy, with all values being 100%. All 3 techniques accurately identified the appropriate mutation in the known control specimens. In summary, all 3 tests are relatively comparable for detecting the KRAS mutation, with Applied Biosystems having a slightly lower sensitivity, negative predictive value, and accuracy than therascreen RGQ and Pyro.