Purpose BRAF mutant metastatic colorectal cancer (mCRC) forms an aggressive subset of colorectal cancer with minimal response to selective RAF inhibitors. Preclinical data show that reactivation of epidermal growth factor receptor (EGFR) signaling occurs in colorectal tumor cells treated with RAF inhibitors and that the addition of an EGFR inhibitor enhances antitumor activity. These data suggest that combined therapy with RAF and EGFR inhibitors could be an effective strategy for treating BRAF V600E mCRC. Experimental Design We undertook a pilot trial to assess the response rate and safety of the BRAF inhibitor vemurafenib combined with anti-EGFR antibody panitumumab in patients with BRAF mutant mCRC. Patients received standard approved doses of panitumumab and vemurafenib. Results Fifteen patients were treated. Performance status was ECOG 0 in four patients (27%) and ECOG 1 in 11 patients (73%). All patients had progressed through at least one standard treatment regimen, and eight (53%) had received previous fluoropyrimidine, oxaliplatin, and irinotecan chemotherapy. Treatment was well tolerated, with less cutaneous toxicity than would be expected with either agent, and no cases of keratoacanthomas/squamous cell carcinomas. Tumor regressions were seen in 10 of 12 evaluable patients with partial responses in two patients (100% and 64% regression lasting 40 and 24 weeks, respectively), and stable disease lasting over six months in two patients. Conclusion Combined RAF and EGFR inhibition is well tolerated, with less cutaneous toxicity than would be expected with either agent, and results in modest clinical activity in this highly aggressive and chemo-resistant subset of CRC.

Background Targeted cancer treatments are almost always first studied in adults, even when there is a biologically plausible potential for efficacy in children. Through compassionate use programs, children who are not eligible for a clinical trial and for whom there are no known effective therapies may obtain access to investigational agents, including drugs under development for adults. However, little is known about pediatric oncologists’ experiences with applying for and obtaining compassionate use agents. Methods This study surveyed 132 pediatric oncologists to assess awareness and utilization of compassionate use programs, to identify barriers to their use, and to evaluate available institutional support and resources. Results We found that the process of applying for access to drugs in development is poorly understood, which presents a barrier to obtaining investigational drugs. Fifty‐seven percent of the pediatric oncologists applied for compassionate use. Providers from larger institutions or with more than 15 years of clinical experience were more likely to complete an application and obtain investigational agents for their patients. Conclusion Identified perceived and actual barriers to compassionate use application submission suggest pediatric oncologists may benefit from educational resources and support to ensure children with cancer equal access to investigational agents and care.

611 Background: BRAF mutant metastatic colorectal cancer (mCRC) is an aggressive subset of colorectal cancer that exhibits minimal response to selective RAF inhibitors. Preclinical data suggest that epidermal growth factor receptor (EGFR) reactivation with RAF inhibition attenuates the efficacy of RAF inhibitors in mCRC and that combined EGFR and RAF inhibition may be a promising therapeutic strategy. Methods: We undertook a pilot trial to assess the response rate and safety of the combination of the selective RAF inhibitior vemurafenib and anti-EGFR antibody panitumumab in patients with BRAF mutant mCRC. Patients received panitumumab 6 mg/kg IV every 14 days starting on day 1 and vemurafenib 960 mg orally twice daily continuously starting on day 8, with treatment staggered for planned correlative studies. Results: Fifteen patients received treatment. Median age was 62 years (range 22-83 years), seven patients (47%) were male, and 11 patients (73%) had a right-sided primary tumor. Performance status was ECOG 0 in four patients (27%) and ECOG 1 in 11 patients (73%). All patients had progressed through at least one standard treatment regimen, and eight patients (53%) had received previous fluoropyrimidine, oxaliplatin, and irinotecan chemotherapy. Acneiform rash (all grade 1 or 2) (53%), fatigue (53%), and arthralgias (40%) were the most frequently observed treatment-related adverse events. Treatment response was assessed in 12 patients because two patients died from disease progression before the first scan and one patient withdrew consent soon after starting treatment. Two patients (13%) had confirmed partial responses (100% and 64% regression) lasting 40 and 24 weeks, respectively. Eight patients (53%) had stable disease (SD) with tumor regression of >15% by RECIST measurement in six of these patients, including two of whom achieved stable disease lasting over six months. Conclusions: Combined RAF and EGFR inhibition is well tolerated and leads to tumor regression in a subset of patients with BRAF mutant mCRC. Planned correlative studies will evaluate degree of pathway inhibition and reactivation of other upsteam pathways with vemurafenib and panitumumab treatment. Clinical trial information: NCT01791309.

Neuroblastoma, the most common extracranial solid tumor of childhood, can present in multiple primary sites, but the extent of genetic heterogeneity among tumor foci, as well as the presence or absence of common oncogenic drivers, remains unknown. Although PHOX2B genetic aberrations can cause familial neuroblastoma, they demonstrate incomplete penetrance with respect to neuroblastoma pathogenesis, suggesting that additional undescribed oncogenic drivers are necessary for tumor development. We performed comprehensive molecular characterization of neuroblastoma tumors from two siblings affected by familial multifocal neuroblastoma, including whole exome sequencing and single‐nucleotide polymorphism (SNP) arrays of tumor and matched blood samples. Data were processed and analyzed using established bioinformatics algorithms to evaluate for germline and somatic mutations and copy number variations (CNVs). We confirmed the presence of a PHOX2B deletion and NF1 mutation across all tumor samples and the germline genome. Matched tumor‐blood whole exome sequencing also identified 365 genes that contained nonsilent coding mutations across all tumor samples, with no recurrent mutations across all tumors. SNP arrays also showed significant heterogeneity with respect to CNVs. The only common CNV across all tumors was 17q gain, with differing chromosomal coordinates across samples but a common region of overlap distal to 17q21.31, suggesting this adverse prognostic biomarker may offer insight about additional drivers for multifocal neuroblastoma in patients with germline PHOX2B or NF1 aberrations. Molecular characterization of all tumors from patients with multifocal primary neuroblastoma has potential to yield novel insights on neuroblastoma pathogenesis.

<p>Supplementary table 2. Tumor genetic mutations identified with next generation sequencing</p>