Kamatham, Saivaishnavi

3566 Background: According to the American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) joint review on circulating tumor DNA (ctDNA) issued in March 2018, widespread use of ctDNA assays in most patients with advanced cancer is still an area of ongoing research. However, multiple studies thereafter published and/or presented support its use in patients with metastatic colorectal cancer (CRC). This has led to several institutions adopting it as ‘clinical practice’. The aim of this study is to report on our institution’s adoption of ctDNA testing for every patient at the time of diagnosis and/or time of progression. Methods: We report on results of 322 CRC patients with 607 ctDNA tests at our center from January 2017 to February 2019 using a commercially available platform (Guardant360). Results: Among 322 patients of our cohort, a total of 607 ctDNA tests were done (Table). 127 (39.4%) of these tests were serial analyses. In the CRC patients who had serial testing, at progression, mechanisms of resistance included acquisition of KRAS, NRAS, EGFR mutations; and HER2- and MET-amplifications. The subclonal mutations were noted to disappear when the selective inhibition was stopped. This was seen in patients on targeted therapies/biologics rather than chemotherapy. This was of value in treatment modification, clinical trial selection and/or monitoring of disease progression in these patients. Conclusions: While ctDNA testing may not be ready for primetime in all advanced cancers, it is increasingly being adopted in practice for especially metastatic CRC. Of particular value is the serial ctDNA testing in the RAS/RAF wildtype subset and now BRAF V600E mutant CRC on anti-EGFR based therapies. [Table: see text]

703 Background: In metastatic colorectal cancer (CRC), pharmacogenomics (PGx) testing presents a unique opportunity to improve outcomes since the genes DPYD & UGT1A1 encoding the enzymes metabolizing the chemotherapy drugs, 5-fluorouracil and irinotecan, are already well known. In the TRIBE clinical trial, proportion of patients with serious adverse events (SAEs) was higher in those with DPYD/UGT1A1 aberrations and were dose dependent. Critical barrier has been integration into clinical practice. We aimed to report on the feasibility and results of incorporating PGx testing into clinical practice. Methods: As a quality improvement initiative, we integrated the use of OneOme RightMed comprehensive test through funding from our center of individualized medicine, which reports on 28 genes and over 350 medications of interest. Pharmacists provided dosage recommendations based on test results real-time. Results: 126 patients have had the PGx testing since November 2017. Results have been available within 3-5 days. The table outlines the analyzed results thus far of variants in UGT1A1 and the DPYD-genes alongside the CYP450 genes. Of these, 59% had a DPYD/UGT1A1 aberration and 100% had at least one actionable aberration related to supportive care medications from all possible medications listed on their PGx report. Conclusions: Preemptive comprehensive PGx testing can be integrated into clinical practice in real-time for cancer patients. This sets the stage for a prospective randomized clinical trial to demonstrate the amount of benefit this can result in these patients. [Table: see text]

660 Background: Adverse toxicities to chemotherapy remain a limiting factor for patients receiving treatment for malignancies. In gastrointestinal cancers, particularly metastatic colorectal cancer, the majority of front line treatment remains chemotherapy containing 5-fluorouracil and/or irinotecan. One particular cause that can predispose a patient to increased toxicity from 5-fluorouracil is genetic variation in the DPYD gene, as well as TYMS gene. Similarly, genetic variation in the UGT1A1 gene can increase the risk of irinotecan toxicity. These gene variations may have major implications when deciding on treatment regimens for these types of patients; however, they are not routinely checked. Methods: In Mayo Clinic Florida, patients with metastatic colorectal cancer receiving 5-fluorouracil and/or irinotecan chemotherapy during the period of July 2017-July 2018 were tested for genetic variants in DPYD/TYMS and UGT1A1. This testing was done during routine clinic visit either by buccal swab or blood test. The DPYD/TYMS and UGT1A1 variant results were evaluated together with a pharmacist for recommendations regarding dose reductions on 5-fluorouracil and irinotecan respectively. Results: A total of 292 patients were tested. Total number of patients who had a variation in the DPYD/ TYMS and/or UGT1A1 gene was 169 (57.9%). The UGT1A1 variation was the most prevalent with 154 (52.7%) patients having a variant (115 heterozygous variant, 34 homozygous variant and 5 double heterozygous variant). Specifically there were 3 patients with both UGT1A1 and DPYD variants and 3 patients with both UGT1A1 and TYMS variants. One patient had both DPYD and TYMS variations. Conclusions: Routine pharmacogenomic testing for UGT1A1 and DPYD/TYMS genetic variants should be done in all patients receiving irinotecan and 5-fluorouracil chemotherapy respectively. Avoiding or preemptively dose reducing these agents in patients with gene variations may help prevent toxic adverse events and make treatment more tolerable.

525 Background: The hallmark of circulating tumor DNA (ctDNA) is its rapid turnaround and non-invasive nature. According to American Society of Clinical Oncology (ASCO) and College of American Pathologists joint ctDNA review published in March 2018, there is no sufficient evidence to support the use of ctDNA in practice for GI cancers. However, there were numerous studies presented at ASCO Annual Meeting supporting its value. We aimed to summarizing on its role in the management of gastrointestinal cancers based on the studies presented recently. Methods: We limited our search to keywords ‘ctDNA’, ‘circulating tumor DNA’, ‘cell-free DNA (cfDNA)’ and/or ‘liquid biopsy’, at the 2018 ASCO Annual Meeting library abstracts and presentations. Results: There were 35 studies that revolved around ctDNA as a diagnostic tool, prognostic marker and a measure of tumor heterogeneity in gastrointestinal cancers. Depending on the assay used, the results of several studies showed that ctDNA was able to identify relevant mutations including RAS, HER2/Neu, BRAF, MET, BRCA2, APC, TP53, ROS1, PTEN and NF1. The prognosis in terms of tumor mutation burden, objective response rate, metastasis and survival was also estimated based on ctDNA. The findings showed that higher baseline ctDNA levels and/or increased number of mutations detected in ctDNA were associated with poor survival and multi-site metastasis. Right-sided colon cancer was associated with higher number of mutations in ctDNA than left-sided colon and rectal cancers. Similarly, tubular adenocarcinoma subtype of gastric cancer was more likely to have higher ctDNA levels than signet-ring cell subtype. The response to therapy and the residual metastatic disease which was otherwise not detected on imaging could be detected by ctDNA as well. Conclusions: The research at ASCO 2018 report an increasingly promising role of ctDNA in many forms in patients with gastrointestinal malignancies. Experts at the meeting argued that this may well indeed be ready for prime time for certain GI malignancies including colorectal cancers. Prospective studies and studies showing its feasibility into practice can potentially help revise the current guidelines.