Dataset Information

Phase II Pilot Study of Vemurafenib in Patients With Metastatic BRAF-Mutated Colorectal Cancer.

ABSTRACT:

Purpose

BRAF V600E mutation is seen in 5% to 8% of patients with metastatic colorectal cancer (CRC) and is associated with poor prognosis. Vemurafenib, an oral BRAF V600 inhibitor, has pronounced activity in patients with metastatic melanoma, but its activity in patients with BRAF V600E-positive metastatic CRC was unknown.

Patients and methods

In this multi-institutional, open-label study, patients with metastatic CRC with BRAF V600 mutations were recruited to an expansion cohort at the previously determined maximum-tolerated dose of 960 mg orally twice a day.

Results

Twenty-one patients were enrolled, of whom 20 had received at least one prior metastatic chemotherapy regimen. Grade 3 toxicities included keratoacanthomas, rash, fatigue, and arthralgia. Of the 21 patients treated, one patient had a confirmed partial response (5%; 95% CI, 1% to 24%) and seven other patients had stable disease by RECIST criteria. Median progression-free survival was 2.1 months. Patterns of concurrent mutations, microsatellite instability status, CpG island methylation status, PTEN loss, EGFR expression, and copy number alterations were not associated with clinical benefit. In contrast to prior expectations, concurrent KRAS and NRAS mutations were detected at low allele frequency in a subset of the patients' tumors (median, 0.21% allele frequency) and were apparent mechanisms of acquired resistance in vemurafenib-sensitive patient-derived xenograft models.

Conclusion

In marked contrast to the results seen in patients with BRAF V600E-mutant melanoma, single-agent vemurafenib did not show meaningful clinical activity in patients with BRAF V600E mutant CRC. Combination strategies are now under development and may be informed by the presence of intratumor heterogeneity of KRAS and NRAS mutations.

SUBMITTER: Kopetz S

PROVIDER: S-EPMC4669589 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Parallel activation of the phosphatidylinositol 3-kinase-mammalian target of rapamycin pathway represents a mechanism of primary and acquired resistance to BRAF-targeted therapy, but the two pathways have yet to be cotargeted in humans. We performed a phase I study to evaluate the safety and activity of the BRAF inhibitor vemurafenib in combination with the mammalian target of rapamycin inhibitor everolimus in BRAF-mutated advanced solid tumors. We performed a 3+3 dose-escalation study with escalating doses of both oral (PO) vemurafenib administered twice a day and PO everolimus administered daily. Twenty patients with advanced cancers were enrolled. The median adult age was 64 years (range, 17 to 85 years); two pediatric patients were 10 and 13 years old. Patients were heavily pretreated with prior BRAF or MEK inhibitors (n = 11), phase I clinical trial therapy (n = 10), surgery (n = 18), radiation therapy (n = 11), and chemotherapy (n=13). One of the two pediatric patients initially experienced grade 3 rash, but after dermatologic intervention, the patient remains on trial with partial response and no dose reduction at time of analysis. Four dose-limiting toxicities (rash, n = 1; fatigue, n = 3) were observed at dose level 2. Therefore, dose level 1 (vemurafenib 720 mg PO twice a day and everolimus 5 mg PO daily) was the maximum-tolerated dose. Overall, four patients (22%) had a partial response and nine patients (50%) had stable disease as best response. One pediatric patient with pleomorphic xanthroastrocytoma remains on protocol with continued clinical response after 38 cycles. The combination of vemurafenib 720 mg PO twice a day and everolimus 5 mg PO daily is safe and well tolerated and has activity across histologies, with partial responses noted in advanced non-small-cell lung cancer, melanoma, optic nerve glioma, and xanthroastrocytoma, including patients who previously experienced progression on BRAF and/or MEK inhibitor therapy. Further investigation in a larger cohort of molecularly matched patients is warranted.