164000-176

Prospective evaluation of circulating cell-free DNA sequencing in patients with metastatic renal cell carcinoma treated with pazopanib plus abexinostat.

Subcategory: 
Category: 
Genitourinary (Nonprostate) Cancer
Session Type and Session Title: 
Poster Session, Genitourinary (Nonprostate) Cancer
Abstract Number: 

4551

Poster Board Number: 
Board #173
Citation: 
J Clin Oncol 34, 2016 (suppl; abstr 4551)
Author(s): 
Jim Leng, Armand Harb, Kamran Abri, Ilaria Mastroserio, Anne Reinert, Jennifer A. Grabowsky, Charles J. Ryan, Terence W. Friedlander, Amy M. Lin, Richard Burnham Lanman, Kimberly C. Banks, Rahul Raj Aggarwal, Pamela N. Munster; University of California, San Francisco, San Francisco, CA; UC San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, CA; UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, San Francisco, CA; Guardant Health, Inc., Redwood City, CA

Abstract Disclosures

Abstract: 

Background: Renal cell carcinoma (RCC) exhibits somatic alterations in genes controlling hypoxia and chromatin states including VHL. Analysis of circulating cell-free DNA (cfDNA) as a means to detect these and other potentially actionable mutations in RCC across histologic subtypes has not been previously fully characterized. Methods: cfDNA was isolated from pretreatment and post-progression plasma samples of sixteen patients with metastatic RCC (N = 12 clear cell; N = 4 papillary) enrolled on a clinical trial of pazopanib and abexinostat (NCT01543763) and analyzed using a cfDNA next-generation sequencing (NGS) panel of 68 genes (Guardant Health). The lower limit of detection was 0.1% mutant allele frequency (MAF) at each nucleotide position. Results: 16 pretreatment and 5 post-progression samples were evaluable. 49 somatic mutations were reported across the entire cohort (mean = 3.06 mutations per patient; range: 0-7). Somatic alterations were detected in 94% (n = 15) of pretreatment samples and 4 of 5 post-progression samples with mean cfDNA MAFs of 0.70% (range = 0.1% - 5.6%) and 1.65% (range 0.10-5.5%) respectively. The most frequently mutated genes were VHL (44% of patients), TP53 (38%), FGFR2 (38%), and KRAS (19%). Evidence of PI3K pathway activation was detected in 25% of pts (N = 2 with activating PIK3CA mutations; N = 2 with PTEN loss-of-function). Activating mutations in MET and IDH1 were identified in two of the four pts with papillary RCC. 2 of 5 pts analyzed to date had novel somatic mutations detected at the time of progression. Conclusions: Analysis of cfDNA in metastatic renal cell carcinoma yields similar frequency of VHL mutations compared to TCGA, as well as potentially actionable mutations across both clear cell and papillary RCC subtypes. PI3K pathway alterations are common and suggest the potential to select patients for combination PI3K/VEGF targeting approach. Detection of novel, actionable mutations using cfDNA at the time of progression is feasible and may provide insights into mechanisms of resistance by non-invasive methods. Longitudinal analysis of the entire study cohort and correlations with radiographic response are ongoing. Clinical trial information: NCT01543763