Citations

Introduction: Pharmacogenomics is about selecting the “right drug in the right amount for the right patient.” In metastatic colorectal cancer, germline pharmacogenomics testing presents a unique opportunity to improve outcomes, since the genes dihydropyrimidine dehydrogenase and UDP-glucuronosyltransferase metabolizing the chemotherapy drugs, 5-fluorouracil, and irinotecan are already well known. In a retrospective analysis of the landmark TRIBE clinical trial [(TRIBE - TRIplet plus BEvacizumab multicenter, phase III trial by the Italian Cooperative GONO (Gruppo Oncologico Nord Ovest) group (NCT00719797)], the proportion of patients with serious adverse events was higher in those with dihydropyrimidine dehydrogenase/UDP-glucuronosyltransferase aberrations and was dose dependent. We aimed to report on the feasibility and the results of incorporating pharmacogenomics testing into clinical practice. Methods: As a quality improvement initiative and a center of individualized medicine grant, we integrated the use of OneOme RightMed comprehensive test, which reports on 27 genes related to pharmacogenomics and over 300 medications of interest. We limited initial testing to patients with colorectal cancer. Pharmacists provided dosage recommendations based on test results in real-time. Results: At our cancer center, 155 patients underwent pharmacogenomics testing from November 2017 to January 2019. Results were available within 3 to 5 days of testing for most patients and were integrated into treatment decision-making. Of 155 sampled participants, a total of 89 (57.4%) participants had an UGT1A1 variant genotype, NM_000463.2: c.-53_-52[8] *1/*28, n = 74 (47.7%); *28/*28, n = 15 (9.7%). Additionally, 4 (2.6%) participants were heterozygous for dihydropyrimidine dehydrogenase. Two (1.3%) individuals were heterozygous for both UDP-glucuronosyltransferase and dihydropyrimidine dehydrogenase genes. All (100%) the patients had at least 1 actionable aberration related to supportive care medications ( CYP-family) of all the possible medications listed on their pharmacogenomics report. Conclusion: Preemptive comprehensive pharmacogenomics testing can be integrated into clinical practice in real-time for patients with cancer given faster turnaround and low cost. Pharmacist-driven, patient-specific medication management consults add further value given the number of genes/drugs. This sets the stage for a prospective randomized clinical trial to demonstrate the amount of benefit this can result in these patients.

Abstract Doublet chemotherapies are the mainstay in the management of metastatic anal cancer. Immunotherapy has been incorporated into guidelines in a refractory setting. Treatment options remain limited with tumor progression beyond immunotherapy. Modified docetaxel, cisplatin, and fluorouracil (mDCF) chemotherapy, after progression postimmunotherapy, has shown a near‐complete response in our patient with metastatic anal cancer. This likely is secondary to the sequence of immunotherapy followed by chemotherapy that is yielding greater than historical responses.

e15067 Background: There has been a concerning rise of colorectal cancer (CRC) in young individuals (<50 years). There appears to be a preponderance of left-sided tumors and rectal cancers, however, the etiology and biology is not entirely known. Our aim was to describe the results of circulating tumor DNA based (ctDNA) testing in young-onset CRC. Methods: We studied the results of 186 patients with CRC who had ctDNA testing, of whom 41 (22%) had young-onset CRC from January 2017 to January 2019 at Mayo Clinic, Florida. They were categorized based on their age at diagnosis. Results: The age distribution and the aberrations seen are summarized in the table. 25 (61%) were left sided, 9 (22%) were right sided, 7 (17%) were rectal tumors. ctDNA testing was able to identify mutations in 4 (9.8%) patients with BRAFV600E, 8 (19.5%) with RAS and categorized 29 (70.7%) as RAS/RAF wild-type. Furthermore, amplifications were detected in MYC 6 (14.6%) , MET 3 (7.3%) and ERBB2 1 (2.4%). 3(7.3%) were MSI-High and there were 4 individuals with BRCA1/2 noted on ctDNA testing. Conclusions: ctDNA testing for young onset CRC is feasible and identifies a spectrum of clinically meaningful and actionable aberrations. These can further be of use to evaluate treatment response, progression or help in selection of clinical trials. [Table: see text]

e15066 Background: Circulating cell-free tumor-DNA (ctDNA) testing (‘liquid biopsy’) is increasingly being employed both in clinical trials as well as clinical practice. We aimed to contrast and compare the differences in the number of somatic mutations observed on ctDNA testing between mismatch repair deficient/microsatellite instability-high (dMMR/MSI-High) versus mismatch repair proficient/microsatellite stable (pMMR/MSS) colorectal cancers (CRC). Methods: We had 20 patients at Mayo Clinic Florida that were dMMR/MSI-High with testing through the commercially available platform (Guardant360) that uses a 73-gene panel. Median numbers of somatic mutations were compared between the 2 subset of CRC. Results: Patients with dMMR/MSI-High CRC had a median of 8 mutations (range: 2-15) versus a median of 4 mutations (range: 1-22) in pMMR/MSS patients, p-value of 0.001. Similarly, the mean number of somatic mutations were 7.47 (S.D. ± 4.15) versus 5.02 mutations (S.D. ± 3.83) in patients with dMMR/MSI-H and pMMR/MSS, tumors respectively. Though it is simplistic, we could still potentially identify patients who may be candidates for immunotherapy by gauging the mutational burden reported (Table). Furthermore, on serial testing, decline in mutational burden as early as few weeks into therapy was predictive of response later on imaging. Conclusions: Analysis of number of somatic mutations on ctDNA testing can be complementary to MMR/MSI-testing, especially in situations when tissue is not available or safe to obtain. This can also be of value in predicting and/or following response to immunotherapy. The utility of this may go beyond CRC in identifying patients who may benefit from immunotherapy. [Table: see text]

e15065 Background: Colorectal cancer (CRC) is a heterogeneous disease. Specifically for patients with BRAF-V600E mutations and/or mismatch repair deficiency or microsatellite instability-high (dMMR/MSI-High), there have been significant advances in terms of treatment options. Early identification of these subsets of patients has both prognostic and predictive value. We wanted to highlight an observation of utilizing 2 simple, rapid and universally available lab tests i.e. carbohydrate cancer antigen 19-9 and carcinoembryonic antigen tumor markers, the ratio (CA-19-9/CEA) of which can distinctly identify these patients. Methods: We included and analyzed the ratio of CA-19-9/CEA levels in patients with metastatic CRC at Mayo Clinic from December 2016 to February 2019, where both the results were available. Non-parametric tests were done to compare and contrast the differences in the median ratio and tumor marker levels. Results: BRAF-V600E mutant CRC patients had a discordantly profound elevation in CA-19-9 levels as opposed to the CEA levels. The median CA-19-9/CEA ratio was 20 (range: 0.3-167.3) in BRAF-V600E MSS patients as opposed to 4.40 (range: 0.003-216.2) in all other patients, p-value of 0.007 (Table). Similarly, the mean CA-19-9/CEA ratio for BRAF V600E MSS tumors was 57.15 (S.D.± 62.76) versus 10.5 (S.D.± 33.90) for all other types. Furthermore, this discordant elevation is not seen in BRAF-mutant MSI-High or any MSI-High patients (median CA-19-9/CEA ratio - 0.46). Conclusions: To date, this is the first report utilizing the ratio of tumor markers CA-19-9/CEA as predictive rather than just prognostic markers. It clearly identifies BRAF-V600E MSS and the MSI-High CRC patients from other subsets.[Table: see text]

e15063 Background: Bone metastasis from colorectal cancer is a relatively rare phenomenon. The aim of this study is to identify the risk factors and survival patterns of bone metastasis after colorectal cancer diagnosis. Methods: A total of 23,846 colorectal cancer patients who were diagnosed between 1972 and 2017 at Mayo Clinic were included in the analysis. Freedom from bone metastasis since diagnosis at 5, 10, 15, 25 and 35-years were estimated using Kaplan-Meier method. Multivariable Cox regression models were used to assess the differences in overall survival rate for patients with different cancer sides and cancer locations. All tests were two-sided with alpha level set at 0.05. Results: A total of 798 (3.3%) patients had a diagnosis of bone metastasis after colorectal cancer diagnosis over a median follow up of 3.2 years. Thirty-five year freedom from bone metastasis was 83% (95%CI: 80%-86%) for all patients, and were 87.13%, 82.29% and 77.26% for left colon, right colon and rectal cancer patients. Male gender, recent surgical years, and higher cancer stage were associated with higher risk of developing bone metastasis after colorectal cancer diagnosis. Rectal cancer patients had higher hazard of developing bone metastases compared to left and right colon cancer patients. Conclusions: We were able to identify several patient and tumor-related factors associated with the development of bone metastasis in patients with colorectal cancer. The proportion and factors identified are similar to other studies. Future directions would be to analyze other molecular determinants within this subset of patients.[Table: see text]

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]

Background. Individuals after solid organ transplant may develop secondary malignancies. In our clinical practice, we noted an increasing number of individuals who developed colorectal cancers after solid organ transplantation. The primary aim of this study was to describe the characteristics and outcomes of the patients who developed colorectal cancer after solid organ transplant. Materials and Methods. Data was gathered and merged from several registries at Mayo Clinic to identify all patients who received a diagnosis of colon or rectal cancer and solid organ transplant. Continuous variables were summarized as mean (standard deviation) and median (range), while categorical variables were reported as frequency (percentage). Time to colorectal cancer after transplant and overall survival after cancer diagnosis were estimated using Kaplan-Meier method. Results. Initially, 115 colorectal cancer patients who also had a transplant were identified. The diagnosis of colorectal cancer was noted after solid organ transplant in 63 patients. The mean age at transplant was 57 years. Majority had received a kidney transplant (44.4%) followed by liver (36.5%). The median time to develop colorectal cancer was 59.3 months (range: 4.4-251.4 months). 15 (24.6%) were stage 4 at diagnosis and 13 (21.3%) had stage 3 colorectal cancer. Median overall survival was 30.8 months; 5-, 10- and 15-year survival were noted to be 42.5%, 17.9%, and 7.5%, respectively. None of the stage 4 patients were alive at 5 years; 5-year survival rate for stage 1, 2, and 3 patients was 77%, 50%, and 42%, respectively. Conclusions. Our study reports on one of the largest cohorts of patients of colorectal cancer that developed the cancer after solid organ transplant. Survival is extremely poor for advanced cases. However, long-term survivors are noted who developed the cancer at a relatively early stage. Colorectal screening recommendations may need to be revised for patients after solid organ transplant.

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.