Pattern of recurrence after curative resection of stage I-III duodenal adenocarcinoma

794

Background: Duodenal adenocarcinoma (DA) is a rare cancer with limited data regarding the pattern of disease recurrence following resection. Methods: A retrospective review of 115 patients with Stage I-III DA from 3/1994 to 6/2018, at a single high-volume cancer center was conducted. Only patients (pts) who underwent a potentially curative surgical resection (R0/R1 margins) and had a postoperative follow-up radiographic evaluation were included. Periampullary adenocarcinomas were excluded. Clinicopathologic features and patterns of recurrence were compared across cohorts. Results: Of 76 patients who met inclusion criteria, 7 (9%) were stage I, 25 (33%) stage II, and 44 (57%) stage III. Histologic grade was moderate in 58% and poor in 38%. Median age was 63 years (range, 29-84), 38% were female, and R0 resection was 97%. Neoadjuvant therapy was given to 14% and adjuvant therapy to 61%. Radiation therapy (XRT) as either adjuvant/neoadjuvant therapy was used in 27%. Median follow-up was 44 (6-293) months. Median time to recurrence was 11mo, with 84% of recurrences occurring within 2 years. Median time to local recurrence (LR) vs. distant recurrence (DR) was 11mo vs. 12mo, respectively, p = 0.42. Stage impacted recurrence rate: 0% in stage 1 vs. 50% stage 2 vs. 71% stage 3 (p = 0.002). Median time to recurrence was 16mo for stage II and 11mo for stage III (p = 0.04). In total, 4 (5%) pts had LR only, 8 (10%) had LR concurrent with DR, and 32 (42%) had DR only. Recurrence distribution was similar across stage II (LR 8%, LR+DR 15%, DR 77%) and stage III (LR 10%, LR+DR 19%, DR 71%). LR was similar in patients that received XRT (10%) compared to those who did not (9%). Most common sites of DR were peritoneal (38%), liver (33%), distant lymph nodes (12%), and lung (10%). Conclusions: The recurrence pattern for resected DA is predominantly distant metastatic disease with the majority of recurrences occurring within the first two years. Future therapies should focus on improved systemic therapy, and surveillance should be most intensive in the first two years.

NeoRAS: Incidence of RAS reversion from RAS mutated to RAS wild type

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Background: RAS mutations are found in ~50% of patients (pts) with metastatic colorectal cancer (mCRC) and associated with resistance to anti-EGFR. Circulating tumor DNA (ctDNA) enables detection of resistant RASMUT arising from RASWT. Recently there has been interest in defining the converse: RASMUT tumors that revert to RASWT, with early results suggesting rates of ~7%. Clinical trials in this population are in development, though the incidence has not been validated with robust methodologies. Methods: 1) We identified 74 mCRC pts with baseline RASMUT and longitudinal ctDNA or tissue data enrolled in ATTACC (NCT01196130), a prospective genomic matching protocol utilizing paired tissue/ctDNA samples at baseline. We evaluated serial samples for RAS loss. 2) Using an external cohort of pts with mCRC and serial ctDNA with a targeted NGS assay sequencing all KRAS/ NRAS exons (Guardant360, Guardant Health), we screened pts for baseline RASMUT with no evidence of prior anti-EGFR exposure and evaluated for RAS loss. Results: 74 pts met criteria of RASMUT CRC with serial samples in ATTACC. Of these, 51 retained RASMUT. 22 pts had very low or absent levels of other clonal alterations such as APC or TP53 and are therefore unable to reliably detect RAS loss. One patient had true RAS loss with NRAS G13R, APC and TP53 mutations at baseline and persistent high-level APC and TP53 mutations without a detectable NRAS mutation, for an overall rate of RAS loss of 2% (1/52). In the second cohort we identified 162 pts, 34 of which had insufficient ctDNA to assess RAS loss on the serial sample as defined by loss of clonal alterations like APC and TP53. Of the remaining 128 patients, 11 had RAS loss (8.5%, with 1 NRAS, 10 KRAS). We next compared the relative mutant allele frequency (rMAF) between RAS retainers and RAS loss. The median baseline rMAF for pts who lost RAS was 0.74, compared to 0.86 in pts retaining RAS (p = 0.045). Conclusions: RAS reversion in mCRC from RASMUT to RASWT is uncommon and occurs at a rate between 2-8% in our two cohorts. RAS reversion is associated with a lower rMAF at baseline, suggesting subclonality. Liquid biopsies must be interpreted carefully, such that a determination of RAS mutation status is most informative in the presence of truncal APC and/or TP53 mutations.

Prospective study for comprehensive genomic profiling (GP) in cancer of unknown primary (CUP): Feasibility, molecular landscape, and clinical utility in current era

834

Background: CUP presents a unique niche and challenge for application of GP. Absence of a primary limits consensus regarding site-directed and availability of tissue specific targeted therapy. We evaluated the real time feasibility and clinical utility of GP in CUP. Methods: Treatment eligible CUP pts were prospectively enrolled. A novel next-gen targeted sequencing (NGS) assay (ActionSeq/FusionSeq) was used to find genomic alterations (GAs) (somatic mutations in 212 and fusions in 53 cancer-associated genes). The primary objective was to determine prevalence of GAs and to assess the clinical impact via change in pre-test planned therapy (either referral to biomarker pertinent clinical trial (CT) or off label use of FDA approved drugs). With 54 pts we achieved 80% power (α 0.05) to a treatment change in 10% (5% to 15%) pts. Results: Between 9/2016 and 8/2019, 150 pts were consented. Tissue for GP was available in 59 (39%) pts (for 91 pts, samples had exhausted or insufficient tissue). Test was successfully performed on 54 (92%) pts. Cohort characteristics include: median age: 58 yr, male 43%, ECOG PS ≤1 96%, median IHC 8 (range 2-26), median survival 33 m (95% CI 18-47). Median reporting time was 23 days. Four (7%) pts had no identifiable GAs. A fusion ( PTRPK) was seen in 1 (2%) pt. Among 50 pts, total number of GAs were 487; 123 (26%) were “clinically relevant” (median 2.5/pt, range 1-11) while 364 (76%) were variants of unknown significance. Of the 123 GAs, 94 were mutations and 29 were amplifications. The 5 most common mutations were TP53, KRAS, PIK3CA, ARID1A, and NRAS and amplifications were CCND1, FGFR3, ERBB2, EGFR, and MYC. Planned therapy change post ActionSeq occurred in 13 pts (22%, 95% CI 13-34) (2 received an off-label drug; 9 were CT eligible [2 enrolled, 5 had PS decline, 2 pending]; 2 were lost to follow-up). Responses were seen in 2 of 4 pts who received GP based treatment. Conclusions: Comprehensive GP should be offered early to CUP pts. GP can help identify novel therapy and clinical trial options. Given the high rate of insufficient tissue cases, integrating a tissue sensitive algorithm involving IHC and GP in therapeutic management of CUP is merited.

Value appraisal of FDA approved cancer drugs over the past decade

115

Background: Value based drug pricing is emerging as an imperative health care precept in recognition of the ever-increasing drug costs, especially in oncology. Though novel therapies are regularly approved based on benefit, they are often associated with physical and financial toxicities to patients. We aimed to assess the value of FDA approved oncology drugs defined as their expected clinical benefit compared to their toxicities and costs. Methods: We reviewed all new cancer drug approvals by the FDA from 7/2008-6/2018. Current analysis was restricted to approvals based on overall survival (OS) and progression-free survival (PFS). Data regarding approval indication, effect size, and toxicity were collected from FDA website and publications. Toxicity was estimated as adverse events ≥ grade 3 (or serious adverse events) as reported. Micromedex RED BOOK was used to estimate the total drug price using 2018 average wholesale prices. Price was estimated over 3 months to account for difference in drug regimens. Results: Among the 231 trials used by FDA for approvals in oncology, 115 had OS or PFS as their primary endpoint. Median patients per trial was 539. Of 79 trials with a PFS endpoint, the median HR was 0.50 (range: 0.15 - 0.91); median 3-month drug price was $45,903.72. Compared to the control arm, median toxicity for new drugs was 7% higher (range: -34.4 - 55%). Correlation of HR benefit to 3-month price was 0.06 (95% CI: -0.17 - 0.28, P = 0.61). Correlation of net toxicities to 3-month price was 0.01 (95% CI: -0.25 - 0.26, P = 0.94). Of 43 trials with an OS endpoint, the median HR was 0.72 (range: 0.37 - 0.94); median 3-month price was $43,523.46. Relative to control arm, median toxicity for new drugs was 4% higher (range: -34.4 - 45.8%). Correlation of HR benefit to 3-month price was 0.38 (95% CI: 0.08 - 0.62, P = 0.012). Correlation of net toxicities to 3-month price was -0.12 (95% CI: -0.45 - 0.24, P = 0.50). Conclusions: Drug approvals in oncology come with a high cost and drug prices have very little correlation with estimated benefit in outcomes and toxicities. As policies evolve to promote higher value in health care, attention should be paid to benefits of drugs in relation to pricing and using biomarker-based patient selection to maximize benefits and minimize toxicities.

Randomized, open-label, perioperative phase II study evaluating nivolumab alone or nivolumab plus ipilimumab in patients with resectable HCC

4098

Background: In HCC, surgical resection is associated with high recurrence rate, and no effective neoadjuvant or adjuvant therapies currently exist. On the basis of of previous reports on the efficacy and safety of anti–PD-1 (nivolumab) and anti–CTLA-4 (ipilimumab) antibodies against HCC, we initiated a randomized pilot trial of perioperative immunotherapy for resectable HCC. Methods: This is a randomized, phase II pilot trial of nivolumab (Arm A) or nivolumab + ipilimumab (Arm B) as pre-operative treatment for patients (pt) with HCC who are eligible for surgical resection. Pt are given nivolumab 240 mg every 2 weeks (wk) for a total of 6 wk. Pt in Arm B are treated concurrently with ipilimumab 1 mg/kg every 6 wk. Surgical resection occurs within 4 weeks after last cycle of therapy. Pt continue adjuvant immunotherapy for up to 2 years after resection. Primary objective is the safety and tolerability of nivolumab +/- ipilimumab. Secondary objectives include overall response rate, complete response rate and time to progression. Exploratory objectives include evaluating the pre- and post-treatment immunological changes in tumor tissues and peripheral blood. Results: 17 pt were enrolled at the time of interim analysis (8 in Arm A, 9 in Arm B) and 14 were evaluable. Most pt (53%) were 60-70yo, and males (70%). 6 pt were HCV-positive and 4 had chronic hepatitis B. 14 pt proceeded with resection as planned; surgery was aborted for 2 pt (1 for frozen abdomen and 1 for development of contralateral liver nodule). One is still receiving preoperative therapy. Pathologic complete response (pCR) was observed in 4/14 evaluable pt – 2 in Arm A and 2 Arm B (29% pCR rate). 4 pt in Arm B and 1 in Arm A experienced grade 3 or higher toxicity prior to surgery. Conclusions: We report a pCR rate of 29% in an interim analysis of a phase II pilot trial of perioperative immunotherapy for resectable HCC. Treatment was safe and surgical resection was not delayed. The study is ongoing and results may contribute to a paradigm shift in the perioperative treatment of HCC. Clinical trial information: NCT03222076.

Clinical and prognostic significance of serum levels of fatty acid binding proteins in hepatocellular carcinoma (HCC)

4099

Background: Limited data are available about the prognostic effect of fatty acid binding proteins (FABP) in viral and non-viral-related hepatocellular carcinoma (HCC). Previous studies suggested that selected FABP could be a potential target markers for HCC chemotherapy response and may correlated with presence of cirrhosis and poor outcome. We aimed to test the association between plasma levels of Liver (L)-FABP, Heart (H)-FABP, and Adipose (A) FABP and HCC. Methods: we enrolled 767 HCC patients from MD Anderson Cancer Center. Under IRB approval, baseline patients’ characteristics were retrieved from medical records and blood samples were collected and tested form plasma levels of L-, A-, H-, FABPs. Descriptive statistics were performed and the median values of FABPs among 200 normal controls (NC) were used as cutoff values of FABPs. Overall survival (OS) was estimated by Kaplan Meier curve and log rank test. Results: FABPs were highly expressed in HCC cases than controls. Mean values (±SE) of AFABP, HFABP, and LFABP were significantly higher in cases [25.6 (.7), 10.8 (.5), and 47.8 (1.9)] than controls [19.1 (.8), 7.7 (2), 22. 9 (.5)], P < .001. All FABPs were significantly associated with cirrhosis, higher Child Pugh Score (CTP), advanced stage in Barcelona clinic liver cancer stage (BCLC), higher AFP levels, vascular invasion and thrombosis, and tumor nodularity. Median OS (months) (95%CI) were significantly short in patients with higher level of AFABP, HFABP, and LFABP [9.3 (6.8-11.9), 9.4 (6.8-11.9), and 11.1 (8.8-13.3)] as compared to patients with low levels [16.4 (13.8-18.9), 16.4 (14.2-18.6), and 17.9 (14.9-20.9) respectively (P < .01). The significance was observed in non-viral related HCC for LFABP and HFABP, but not AFBABP. Conclusions: To the best of our knowledge, we describe the largest study correlating FABPs levels with clinical and prognostic characteristics of HCC. Higher levels were associated with poor survival. These findings suggest that LFABP and HFABP may be used as potential prognostic biomarkers for non-viral-related HCC.

Outcomes and patterns of failures after hypofractionated radiation therapy for intrahepatic cholangiocarcinoma

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Background: Locally advanced unresectable intrahepatic cholangiocarcinoma (IHCC) remains incurable. Prior data has shown the effectiveness of hypofractionated radiation therapy (HRT) with biological equivalent doses (BED) greater than 80.5 Gy in improving local control and survival for this patient population. This is an updated report of our IHCC experience with HRT in 15 or 25 fractions using a simultaneous integrated boost technique. Methods: A retrospective analysis of 63 patients (median age 64, range 29-87) diagnosed between 2007-2016 who received HRT was performed. RT dose ranged from 58-90 Gy in 15 fractions and 62.5-100 Gy in 25 fractions, translating to a median BED of 97.5 (range 78.1-144 Gy). Median primary tumor size at diagnosis was 7.8 cm (2.4-17cm). Forty-eight (76%) patients received gemcitabine-based therapy prior to HRT. Results: Median follow up was 31 months (4-110). The 2 year overall-survival (OS), local-progression-free-survival (LPFS), intrahepatic-distant-metastasis-free-survival (IH-DMFS) and extraheptic-distant-metastasis-free-survival (EH-DMFS) were 71% (95% CI 58-82), 67% (95% CI 50-80), 40% (95% CI 28-54) and 40% (95% CI 27-54) respectively. Pattern of failure analysis revealed 16 patients with local failure after HRT, of which only 5 (8% of total) progressed within the high iso-dose field line (BED > 80.5). After HRT, 41 (65%) patients had intrahepatic metastasis that occurred outside the radiation field, and 34 (54%) patients developed extrahepatic metastasis. On multi-variate analysis, T-stage was an independent predictor of OS, LPFS, IH-DMFS, and EH-DMFS. Larger normal liver volume and 15 fraction treatments were independently associated with better LPFS and IH-MFS respectively. There were no significant HRT-related toxicities. Conclusions: HRT demonstrates safety and efficacy for durable local control and prolonged overall survival in patients with unresectable IHCC. Dominant modes of failure are outside the HRT field. Improvements in systemic therapies could further improve outcomes for this patient population.

FOLFOXIRI versus doublet-regimens in the first-line therapy of MSI-S right-sided (RS) metastatic colorectal cancer (mCRC): A survival analysis

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Background: Microsatellite stable (MSI-S) RS mCRC patients (pts) have a worse prognosis relative to left sided tumors for overall survival (OS). The present analysis aims to test the hypothesis that a triplet-regimen is superior compared to doublet-regimens (DR; FOLFOX or FOLFIRI) for OS. Methods: Pts with treatment-naive RS mCRC at MD Anderson Cancer Center between January/2011 to December/2018 were selected. We compared the progression-free survival (PFS) and OS of mCRC pts treated with FOLFOXIRI versus DR. Pts treated with anti-EGFR therapy were excluded. Results: A total of 37 pts were treated with FOLFOXIRI and 111 pts with DR. There were no statistical difference between groups regarding gender, KRAS and BRAF mutations, peritoneal metastasis and bevacizumab use. There were statistical difference in age (median: 46y vs 59y) and metastasectomy rates (14% vs 32%) (p < 0.001). KRAS mutation was found in 65% of the population. Median follow-up was 55.3m. Median PFS was 6.5m vs 11.2m (HR: 1.30 95% CI 0.85 – 1.99) and median OS was 17.0m vs 26.3m (HR: 1.01 95% CI 0.60 – 1.68). By univariate analysis, pts who have undergone metastasectomy had superior PFS (14.9m vs 9.2m; p<0.001) and OS (32.4m vs 22.9m; p=0.003). By multivariate analysis adjusted for age, BRAF mutation, metastasectomy, bevacizumab use and, treatment regimen, only age and metastasectomy had prognostic influence for PFS (p=0.039 and p=0.026, respectively). Conclusions: Despite RS having a poor prognosis for OS, our study does not suggest that RS mCRC pts benefit from intensive treatment. Randomized clinical trials may suggest more individualized therapies.

Identifying anti-EGFR (EGFRi) response subgroups using evidence of ctDNA selective pressure

3587

Background: Metastatic colorectal cancers (mCRC) that respond to EGFRi display a robust circulating tumor DNA (ctDNA) signature that reflects selective pressure and clonal evolution. Conversely, non-responding tumors do not exhibit this signature. On this basis, we developed a novel method that defines EGFRi sensitivity with improved biological confidence with fewer patients (pts), and does not rely on clinical trial outcomes where responses may be confounded by concurrent chemotherapy. We used this method to further elucidate the association of several features that have been previously reported to be associated with EGFRi resistance, namely tumor sidedness, BRAF, PIK3CA, or ERBB2 ( HER2) MTs, and the absence of APC/ TP53MT. Methods: We analyzed 112 pts with baseline tissue based RASWT mCRC who had progressed following EGFRi, and with plasma samples available for ctDNA sequencing using a blood based NGS assay. Using our previously validated EGFRi exposure signature, we identified pts with evidence of selective pressure. Results: Post EGFRi ctDNA found 37% and 33% of pts with left sided and transverse tumors displayed evidence of selective pressure, respectively. 0 pts with right sided tumors displayed evidence of selective pressure; p= 0.01. Similarly, BRAFV600EMT displayed no evidence of selective pressure vs 30% of WT pts; in contrast, selective pressure was evident in pts with PIK3CAMT, ERBB2MT and pts with absence of APC/TP53MT (42% vs 28%, 67% vs 28%, 24% vs 43%, respectively for MT vs WT, p= NS for all). BRAF, PIK3CA, ERBB2, and APC/TP53 MT were present in 4/117, 12/108, 3/118 and 30/91 pts, respectively. ctDNA shedding was similar for all subgroups, as was time from previous EGFRi, indicating that these factors were not confounders. Conclusions: Consistent with prior large randomized studies, no pts with right sided tumors or BRAFMT had evidence of biologic benefit as assessed by presence of selective pressure. In contrast a number of pts with transverse tumors, ERBB2MT, PIK3CAMT or absence of APC/TP53MT had evidence of EGFR selective pressure, confirming that these are not absolute predictors of EGFR resistance and suggesting a subset of these pts were deriving benefit from EGFR inhibition. This biology based approach has the potential to more efficiently evaluate biomarkers of targeted therapy in the future without reliance on large randomized datasets.

Value appraisal of FDA approved cancer drugs over the past decade

e18385

Background: Value based drug pricing is emerging as an imperative health care precept in recognition of the ever-increasing drug costs, especially in oncology. Though novel therapies are regularly approved based on benefit, they are often associated with physical and financial toxicities to patients. We aimed to assess the value of FDA approved oncology drugs defined as their expected clinical benefit compared to their toxicities and costs. Methods: We reviewed all new cancer drug approvals by the FDA from 7/2008-6/2018. Current analysis was restricted to approvals based on overall survival (OS) and progression-free survival (PFS). Data regarding approval indication, effect size, and toxicity were collected from FDA website and publications. Toxicity was estimated as adverse events ≥ grade 3 (or serious adverse events) as reported. Micromedex RED BOOK was used to estimate the total drug price using 2018 average wholesale prices. Price was estimated over 3 months to account for difference in drug regimens. Results: Among the 231 trials used by FDA for approvals in oncology, 115 had OS or PFS as their primary endpoint. Median patients per trial was 539. Of 79 trials with a PFS endpoint, the median HR was 0.50 (range: 0.15 - 0.91); median 3-month drug price was $45,903.72. Compared to the control arm, median toxicity for new drugs was 7% higher (range: -34.4 - 55%). Correlation of HR benefit to 3-month price was 0.06 (95% CI: -0.17 - 0.28, P = 0.61). Correlation of net toxicities to 3-month price was 0.01 (95% CI: -0.25 - 0.26, P = 0.94). Of 43 trials with an OS endpoint, the median HR was 0.72 (range: 0.37 - 0.94); median 3-month price was $43,523.46. Relative to control arm, median toxicity for new drugs was 4% higher (range: -34.4 - 45.8%). Correlation of HR benefit to 3-month price was 0.38 (95% CI: 0.08 - 0.62, P = 0.012). Correlation of net toxicities to 3-month price was -0.12 (95% CI: -0.45 - 0.24, P = 0.50). Conclusions: Drug approvals in oncology come with a high cost and drug prices have very little correlation with estimated benefit in outcomes and toxicities. As policies evolve to promote higher value in health care, attention should be paid to benefits of drugs in relation to pricing and using biomarker-based patient selection to maximize benefits and minimize toxicities.

A systematic review of surrogate endpoints (SEPs) for overall survival (OS) in metastatic colorectal cancer (mCRC)

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Background: Although progression free survival (PFS) and overall response rate (ORR) are common endpoints in mCRC trials, validation of these as SEPs for OS across the evolving landscape of systemic treatment in mCRC, with novel therapeutics and expanding lines of treatment, is limited. We aimed to evaluate the potential surrogacy of PFS and RR for OS and explore variations across trial factors. Methods: We identified phase 3 randomized trials of systemic therapy in mCRC between 1986 - 2016 from 4 electronic databases. Data regarding endpoints and trial variables were extracted from published reports. Spearman’s coefficient (r) and linear regression were used to evaluate rank correlations between A) PFS and ORR with OS of both treatment and control arms (arm level analysis); B) net improvement in outcomes using hazard ratio (HR) for PFS and relative risk (RR) for ORR with HR for OS (trial level analysis). Results: A total of 128 trials containing 233 and 230 arms reporting on PFS and ORR, respectively, were identified. Arm level analysis revealed that correlation of PFS and ORR with OS was 0.69 (95%CI: 0.6 – 0.7) and 0.79 (95%CI: 0.7 – 0.8), respectively ( P < 0.001). Of 86 trials with reported HR for OS, PFS and ORR ratios were obtained for 84 and 74 trials, respectively. Trial level analysis revealed that correlation of PFS and ORR treatment effect with OS was 0.71 (95%CI: 0.6 – 0.8) and 0.58 (95%CI: 0.4 – 0.7), respectively ( P < 0.001). Level of correlation for PFS and ORR varied with line of therapy, type of therapy and trial size (Spearman r shown in table). Conclusions: Both ORR and PFS are appropriate SEPs for OS for systemic therapy in mCRC but their relative value varies notably with line/type of therapy and study size. Judicious use of these SEPs in clinical trials accordingly to supplant OS may help improve trial designs and performance.[Table: see text]

Association between gene fusions and anti-EGFR resistance signature in colorectal cancer

3564

Background: Acquired resistance to anti-EGFR therapy in metastatic colorectal cancer (mCRC) has been characterized by a circulating tumor DNA (ctDNA) signature including any sub-clonal RAS mutation, co-existing RAS mutations, or co-existing EGFR mutations. Here, we investigated if fusions in ctDNA are associated with this anti-EGFR signature for CRC patients (pts). Methods: 4289 advanced stage CRC pts underwent molecular profiling using a plasma-based NGS assay that included FGFR2, FGFR3, RET, ALK, NTRK1, and ROS1 fusions. Available clinical histories were reviewed. Correlations between fusions and clinicopathological features were measured with a Fischer exact test. Relative frequencies of genomic alterations were compared between fusion-present vs -absent cases with an unpaired t-test. Clonality for a given alteration was called for a relative variant allele frequency (rVAF) > 50 %, while subclonal was defined as < 50% rVAF. Results: 44 unique fusions were detected in 40 (1.1%) of the 3808 pts with alterations present: RET (N = 16), FGFR3 (N = 12), ALK (N = 10), NTRK1 (N = 3), ROS1 (N = 2), and FGFR2 (N = 1). Relative to non-fusion variants detected, fusions were more likely to be subclonal (OR 8.2, p < 0.0001). Mutations associated with a previously reported anti-EGFR resistance were found in FGFR3 (7/12 pts), RET (7/15 pts) and ALK (5/10 pts). In fusion-present cases, co-existing RAS mutations were more likely to be subclonal than non-fusion cases (OR 14, p < 0.0001). EGFR mutations were more common in fusion present cases (OR 3.7, p = 0.0001) and predominantly subclonal (97%). EGFR mutations aggregated to ectodomain sites (85%) previously linked to acquired anti-EGFR resistance. For 27 pts with available clinical histories, 21 (78%) received anti-EGFR treatment prior to ctDNA testing. Conclusions: Actionable fusions using a ctDNA NGS assay were predominantly subclonal and co-existed with subclonal RAS and EGFR mutations. These clinicopathologic features are consistent with a previously validated signature linked to resistance to anti-EGFR therapies in CRC. We hypothesize that fusions may arise as a previously undescribed mechanism of acquired resistance to anti-EGFR therapies in CRC pts.

Association of PIK3CA mutations (mut) with immune engagement and clinical benefit from immunotherapy in microsatellite stable (MSS) colorectal cancer (CRC) patients (pts)

3604

Background: PI3K pathway alterations, PIK3CA mut or PTEN loss, are known to modulate anti-tumor immune microenvironment. MSS CRC pts respond infrequently to immunotherapy, suggesting the presence of a rare MSS immunogenic subset. We investigated the immune repertoire and outcomes on immunotherapy trials in PIK3CA mut MSS CRC pts. Methods: Immune infiltrates and checkpoints were evaluated using quantitative immuno-histochemistry (IHC) on primary CRC. Mutations were assessed by next generation sequencing. PIK3CA mut neoepitopes and HLA allele affinities were predicted using NetMHC 4.0 Server. Outcomes of MSS CRC pts enrolled in 7 immunotherapy trials were assessed. Clinical benefit (CB) was defined as CR, PR or SD of 24 weeks. Time to progression (TTP) was calculated using Kaplan-Meier Method. PIK3CA mut vs wild type (wt) groups were compared using Mann-Whitney U, Fisher’s exact, or Log-Rank tests as appropriate. Results: PI3K alterations were present in 14/40 MSS CRC pts in IHC cohort (7 PIK3CA mut, 33 wt; 7 PTEN loss, 33 intact). The center of PIK3CA mut MSS CRC had higher median densities of CD3+ cells [1112 (IQ range 865-1421) vs 435 (300-744) cells/mm3; P=0.037] and CD8+ cells [554 (331-1200) vs 185 (60-473) cells/mm3; P=0.037] as compared to PIK3CA wt tumors. Intratumoral immune infiltrates did not differ by PTEN IHC staining in MSS CRC. PD-L1 H-scores were also higher in PIK3CA mut MSS CRC [85 (34-114) vs 29 (11-60); P=0.01]. Several activating PIK3CA mut (E542K, E545K, H1047R) were predicted to generate true neoepitopes with high binding affinity to common HLA types. Indeed, among MSS CRC pts enrolled in 7 immunotherapy trials, half (4/8) of PIK3CA mut pts derived CB as compared to 3/35 (8.6%) PIK3CA wt pts (P=0.015). PIK3CA mut pts had trend towards longer TTP (3.8 months in mut vs 2.1 months in wt; P=0.08). CB or TTP did not differ by colon sidedness, monotherapy / combination therapy, number of mut, or mut in other key genes ( APC, SMAD4, TP53, KRAS, NRAS or BRAF). Conclusions: PIK3CA mut MSS CRC are associated with increased cytotoxic T cell infiltration, higher PD-L1 expression, and greater clinical benefit from immunotherapy. Further investigation of immunotherapy outcomes in the context of neoepitope-HLA allele interaction may help identify a subset of PIK3CA mut MSS CRC pts who are likely to benefit from immunotherapy.

Molecular profiling by circulating tumor DNA (ctDNA) and benefit from anti-PD-1 in HCC

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Background: Molecular profiling has defined actionable mutations in HCC, and has the potential to be used for selection of targeted therapies, as well as for the characterization of predictive biomarkers from approved treatments. Noninvasive strategies are critical to HCC given the challenge of obtaining liver biopsies. We investigated whether profiling by ctDNA could provide predictive and/or prognostic information for HCC patients (pt) treated with immune checkpoint inhibitors. Methods: We analyzed blood samples from 22 HCC pt who underwent treatment with anti-PD-1 using comprehensive genomic testing of ctDNA with a commercially-available platform (Guardant Health, CA). Demographic and treatment data were retrospectively collected with the goal of correlating treatment outcomes and drug response (by imaging and/or AFP) with molecular abnormalities. Results: 17/22 (77.3%) were men; median age was 66 years. 21 patients received nivolumab and 1 received pembrolizumab. 9 were HCV positive and 5 were HBV positive. 15/22 patients had > 1 alteration identified. The median number of alterations/pt was 3 (range, 1-8). TP53 was the common altered gene (n = 11) followed by CTNBB1 (n = 8) , TERT (n = 5) KRAS (n = 3) , GNAS (n = 2). Mutations were also seen (n = 1) in KIT, PIK3CA, PTEN, EGFR, NTRK, FGFR2 among others. 6 pt (27.3%) had AFP response and 8 (36.4%) achieved disease control > 12 weeks. Mutations involving KIT, PIK3CA and PTEN were associated with shorter progression-free (PFS) (p < .001 for all) and overall survival (OS) (p = .028 for all), whereas GNAS mutation was associated with shorter PFS (p = 0.019) but not OS. No differences in OS or PFS was observed for other alterations, including the presence of CTNNB1 mutation. There were no correlations between specific alterations and objective tumor response (either by imaging or AFP). 32% of pt were progression-free at 6 months. Median OS was not reached, and 62% were alive after 1 year. Conclusions: Identifying non-invasive predictive biomarkers of benefit to immunotherapy is a priority in HCC. Our data suggest that specific ctDNA alterations can provide predictive information for survival (OS and PFS) on immune checkpoint inhibitors. Further larger studies are warranted for confirmation.

Meat consumption and BRAF mutation status in colorectal cancer

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Background: Consumption of red and processed meat has been associated with increased risk of developing colorectal cancers, but less is known about the association of meat consumption with tumor molecular features. In this study, we tested the association of total meat consumption with molecular features of colorectal cancer and overall survival in a local cohort of patients. Methods: Data on meat consumption were collected using self-directed environmental surveys from patients with stage IV/locally advanced, treatment refractory colorectal cancer who were enrolled on the Assessment of Targeted Therapies Against Colorectal Cancer clinical protocol. Data on tumor molecular features were collected through medical record review. Patients were categorized into low, medium or high meat consumption groups based on servings per day tertile. Associations between tumor molecular features and meat intake were evaluated by Chi-square and logistic regression. Potential effects of meat consumption on overall survival were assessed using Cox Proportional Hazards models. Analyses were conducted with IBM SPSS v25. Results: Patients consumed an average of 0.74, 1.57 and 3.32 servings of meat per day in the low, medium and high categories, respectively. Out of 593 patients with evaluable data, 27 were found to have a BRAF V600E mutation. Total meat consumption differed significantly by BRAF V600E mutation status (p value 0.02) and by sex (p value < .01), but did not differ by tumor location, microsatellite instability, or RAS mutation status. Using logistic regression, we found that compared to patients with the highest level of meat consumption, those in the medium consumption group may be less likely to have a BRAF V600E mutation (OR 0.24; p value 0.08). Although meat consumption may be associated with BRAF mutation status, it was not predictive of overall survival in our analyses. Conclusions: Among patients in our study, meat consumption may be associated with tumor BRAF V600E mutation status but is not directly associated with survival. Additional work is needed to test this association in cohorts including more BRAF mutant cases. If confirmed, this finding may add further insight into the etiology and biology of these tumors.

IGF-Child-Pugh score as a predictor of treatment outcome in advanced hepatocellular carcinoma patients treated with sorafenib

4076

Background: Our recent published studies concluded that Lower levels of Insulin like growth factors-I (IGF-I) is correlated with shorter overall survival (OS) in HCC, and IGF-CP scores assigned based on serum bilirubin, serum albumin level, prothrombin time, and plasma IGF-1 provides better prognostic stratification. Sorafenib is the first frontline drug approved for the treatment of CP class A patients with advanced HCC. CP class A is the standard criterion for active therapy and trials entry in HCC. In this study we aimed at evaluating the predictive ability of IGF-CP to sub-stratify old CP classes and better predict sorafenib outcomes. Methods: Total of101 patients were prospectively enrolled from MD Anderson Cancer Center (MDACC). Blood sample were collected and tested for IGF-I and IGF-CP was calculated into class A, B and C. Median OS and progression free survival (PFS) were analyzed, and log rank test was used to compare PFS and OS between subgroups of IGF-CTP score of patients. Results: Among CP class, patients who were reclassified as IGF-CP (B) (Old A/new B) had significantly shorter OS in months (m) was 7.6m (95% CI= 5.23-26.51m ) and PFS of 2.99m (95% CI=2.53-5.26m) with (P<0.001) in both, as compared to patients’ who classified as class A by both scoring systems (AA), who had OS of 15.43m (95% CI=12.3-31.18m) and PFS of 4.97m (95% CI=3.26-7.2m), (P<0.001) in both. Conclusions: IGF-CTP score sub-stratified CP A class, and provided better prognostic stratification and accuracy than CP score in predicting sorafenib survival outcomes in HCC. This approach may lead to a paradigm shift in predicting efficacy and toxicity of systemic HCC therapies and in stratifying patients for active therapy and selection in HCC clinical trials.

Reporting of patient (pt) characteristics (c) and use of stratification factors (SF) in phase III trials for metastatic colorectal cancer (mCRC): Urgent need for standardization

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Background: An increasing number of pt and tumor c have predictive and prognostic implications in mCRC. However, there is no consensus on their reporting in trial results. Methods: Pt c and SF from 136 phase III trials of systemic therapies (Rx) in mCRC published between 1988 and 2018 (68,326 pts) were collected. Trials were also grouped per publication date (G1: 1988-97; G2: 98 – 2007; G3: 08-18). Patterns of reporting and trends across G were evaluated. Results: Pt c consistently reported were performance status, PS (98.5%), age (92.6%) and gender (90.4%); race (20.6%) & weight/BMI/BSA were not (13.2%). Tumor c frequently reported were metastatic (met) spread (70.6%) while time intervals related to disease course (25%) and synchronous met vs not (19.1%) were omitted. Of note, primary site was largely reported as colon vs rectum (69%) and sidedness or anatomical location was discernable only in 10.3%. Prior Rx reporting focused on chemo (58.5%) with radiation and surgery and reported in 34% & 28.7%. Reporting of prognostic factors was variable and limited: histology grade CEA, alk phos, LDH (range 10.3-15.4%). Only 11.8% of trials reported genomic factors - KRAS MT was included in all with BRAF MT in 4.4%. Of 140 trials used for SF analysis, 115 had ≥ 1 (range 1-7). Common SF were PS (60%), geography /institution (55.7%). Prior Rx (27%), met spread (24.3%) were sometimes used while primary site (7.8%), genomic factors (6.1%) rarely were. Trends across G are per Table. Conclusions: There is marked inconsistency in pt c & SF reporting in mCRC trials. Consensus guidelines will aid in standardization of trial interpretation and future meta-analyses; and will need to be updated based on emerging data. [Table: see text]

The association between female hormonal supplementation and molecular types in colorectal cancer

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Background: In the US, colorectal cancer is the third most common malignancy in women. Postmenopausal hormone use has been associated with decrease in incidence of colorectal cancer however few studies have evaluated the relationship between hormone use and molecular profiles of advanced colorectal cancer. The aim of this study is to evaluate correlations between female hormonal supplementation use and colorectal cancer molecular, clinical, and pathologic features. Methods: We conducted a retrospective case-case study of female patients with metastatic or unresectable, locally advanced colorectal cancer on the Assessment of Targeted Therapies Against Colorectal Cancer (ATTACC) protocol from 2010 to 2017. Post-menopausal hormone use was self-reported in an environmental survey as part of the ATTACC protocol. Molecular, clinical, and pathologic features were obtained through medical record review. Results: Among 258 female patients, 163 (63%) patients reported ever use of female hormonal supplementation. Ever use was significantly associated with BRAF V600E mutant tumors (OR 2.63, p-value 0.04). There was no association with KRAS, NRAS, PIK3CA mutations, microsatellite instability, or CpG island methylation. The mean age at diagnosis of ever users was 54.4 and mean of no supplement was 56.5 (p-value 0.07), indicating no age difference between ever and never users. Conclusions: Despite the overall protective effects of postmenopausal hormone use on colorectal cancer incidence, among those who develop colorectal cancer, our data suggest an association between female hormonal supplementation and BRAF mutation. Further studies are needed to evaluate this relationship in additional cohorts, interrogate the biological basis, and identify whether there is an association with survival of patients with metastatic or locally advanced colorectal cancer with estrogen or progestin supplement use.

Population-based screening for BRAF V600E in metastatic colorectal cancer (mCRC) to reveal true prognosis

3579

Background: BRAFV600E ( BRAF) mutations (mts) portend poor prognosis in mCRC and patients (pts) may die before ascertainment. Since 2014, Vancouver Coastal Health (VCH) has performed reflex hereditary screening of CRCs with BRAF and mismatch repair (MMR) immunohistochemistry (IHC). We evaluated this BRAF mt population-based cohort ( BRAFPOP) to establish the true prognosis of BRAF mts in mCRC. Methods: We reviewed all mCRCs from VCH between 4/2014 and 5/2018 for BRAF by IHC (VE1 antibody). Overall survival (OS) from stage IV diagnosis was compared to mCRCs with next generation sequencing (NGS) determined BRAF mts ( BRAFNGS) from BC Cancer & MD Anderson. BRAFNGS OS did not differ by center (p = 0.77). Results: See table for BRAF cohort baseline characteristic comparison. BRAFPOP pts had worse OS than BRAFNGS pts (HR 2.5, 95% CI 1.6 – 3.9, P < 0.0001). Median OS for all BRAF mt pts was 17.9 mos. Both groups had worse OS than wild type pts (P < 0.0001). 52 (81%) of BRAFPOP pts were referred to oncology, 40 (63%) received chemotherapy, and 12 (19%) had NGS BRAF testing. BRAFPOP pts who had NGS testing with BRAF mts had OS comparable to other BRAFNGS pts (P = 0.89) and better OS than BRAFPOP pts that never had NGS testing (HR 0.37, 95% CI 0.18-0.76, P = 0.030). Pts with BRAF mts and MMR deficiency (dMMR) (n = 40) had worse OS than MMR proficiency (pMMR, n = 202) (1.6, 95% CI 1.0-2.5, P = 0.011). This was driven by BRAFPOP dMMR pts (HR 1.9, 95% CI 0.9-4.0, P = 0.036) as no difference was seen by MMR in BRAFNGS pts (HR 1.3, 95% CI 0.8-2.2, P = 0.30). Conclusions: Current estimates of prognosis for mCRC with BRAF mts likely underestimate its impact due to referral bias for NGS testing. BRAF mts with dMMR are associated with worse prognosis than pMMR. This appears driven by BRAFPOP pts. [Table: see text]

Prediction model for detecting circulating tumor DNA (ctDNA) in metastatic colorectal cancer (mCRC)

3590

Background: While tissue-based assays have yields above 90% in solid tumors, there is less known about factors that influence the sensitivity of ctDNA for detecting mutations. Methods:We retrospectively evaluated mCRC patients (pts) who had plasma-derived NGS utilizing a highly-sensitive targeted 68-73-gene ctDNA assay. In a case-control design, pts with a known mutation on tissue and radiologic evidence of metastatic disease but no detectable ctDNA mutation were matched 1:3 with randomly selected pts with detectable mutations and compared according to clinical, laboratory, and radiologic characteristics. A prediction score for ctDNA detection was built using a binary logistic backward stepwise regression analysis and tested in two independent data sets from different institutions. Area under the curve (AUC) from receiver operating characteristics curves (ROC) were used for internal and external validation. Results: From 416 pts who met inclusion criteria, plasma-derived NGS did not find tumor mutations in 66 cases (15.9%); 198 pts with detectable alterations were selected as controls. After multivariate analysis, the detection of ctDNA was associated with increasing age (OR 1.05; 95%CI 1.02-1.09; p = .001), presence of liver (OR 5.82; 95%CI 2.55-12.49; p < .001) and lymph node metastases (OR 3.28; 95%CI 1.51-7.60; p = .004), archival TP53 mutations (OR = 2.88; 95%CI 1.37-6.17; p = .006). A key determinant was timing of collection relative to disease status: plasma collected in newly diagnosed metastatic disease or after evidence of progression was substantially more likely to have detectable alterations (OR 9.24; 95%CI 4.11-22.40; p < .001); The simplified prediction model performed well in internal (AUC = 0.88) and external validation (AUC = 0.95; 163 pts). Conclusions: Our validated prediction model provides clinicians and researchers with a tool to screen for patients in whom ctDNA testing can outperform tissue-based testing in detecting genomic alterations.

Pertuzumab plus trastuzumab for HER2-amplified metastatic colorectal cancer (MyPathway): an updated report from a multicentre, open-label, phase 2a, multiple basket study

BACKGROUND

Therapies targeting HER2 have improved clinical outcomes in HER2-positive breast and gastric cancers, and are emerging as potential treatments for HER2-positive metastatic colorectal cancer. MyPathway evaluates the activity of targeted therapies in non-indicated tumour types with potentially predictive molecular alterations. We aimed to assess the activity of pertuzumab and trastuzumab in patients with HER2-amplified metastatic colorectal cancer.

METHODS

MyPathway is an ongoing, phase 2a, multiple basket study. Patients in this subset analysis were aged 18 years or older and had treatment-refractory, histologically confirmed HER2-amplified metastatic colorectal cancer with measurable or evaluable disease and an Eastern Cooperative Oncology Group performance status score of 2 or less, enrolled from 25 hospitals or clinics in 16 states of the USA. Patients received pertuzumab (840 mg loading dose, then 420 mg every 3 weeks, intravenously) and trastuzumab (8 mg/kg loading dose, then 6 mg/kg every 3 weeks, intravenously). The primary endpoint was the proportion of patients who achieved an objective response based on investigator-reported tumour responses. Analyses were done per protocol. This ongoing trial is registered with ClinicalTrials.gov, number NCT02091141.

FINDINGS

Between Oct 20, 2014, and June 22, 2017, 57 patients with HER2-amplified metastatic colorectal cancer were enrolled in the MyPathway study and deemed eligible for inclusionin this cohort analysis. Among these 57 evaluable patients, as of Aug 1, 2017, one (2%) patient had a complete response and 17 (30%) had partial responses; thus overall 18 of 57 patients achieved an objective response (32%, 95% CI 20-45). The most common treatment-emergent adverse events were diarrhoea (19 [33%] of 57 patients), fatigue (18 [32%] patients), and nausea (17 [30%] patients). Grade 3-4 treatment-emergent adverse events were recorded in 21 (37%) of 57 patients, most commonly hypokalaemia and abdominal pain (each three [5%] patients). Serious treatment-emergent adverse events were reported in ten (18%) patients and two (4%) of these adverse events (ie, chills and infusion-related reaction) were considered treatment related. There were no treatment-related deaths.

INTERPRETATION

Dual HER2-targeted therapy with pertuzumab plus trastuzumab is well tolerated and could represent a therapeutic opportunity for patients with heavily pretreated, HER2-amplified metastatic colorectal cancer.

FUNDING

F Hoffmann-La Roche/Genentech.

FOLFIRINOX in pancreatic cancer patients age 75 years or older

362

Background: Although FOLFIRINOX (5-Fluorouracil + leucovorin + irinotecan + oxaliplatin) is now the standard of care for patients (pts) with metastatic pancreatic cancer (PC) based on the 2011 study by Conroy et al. which demonstrated improved median overall survival (mOS) (11.1 vs 6.8 months [m] with gemcitabine, P < 0.001), pts > 75 yrs old were excluded from this study. As per SEER 2011-2015 data, 38% of new PC cases are diagnosed in pts age > 75. The purpose of this study was to assess the safety and efficacy of FOLFIRINOX in this group of pts. Methods: We retrospectively analyzed unresectable PC pts, age ≥ 75, treated with FOLFIRINOX at MD Anderson since 2011. Data obtained include demographics, line of treatment (tx), starting dose, progression free survival (PFS), OS and toxicities. Response was determined by chart documentation. Primary outcomes were mOS and rates of grade 3/4 hematologic toxicity (HT). Results: A total of 24 pts (19 male) were included with median age of 76 (range 75 to 84). 18 had metastatic disease, and FOLFIRINOX was the 1st line of tx for 18 of the 24 pts. The median number of cycles administered was 4 (range 1 to 12). The most frequent starting doses of infusional 5-FU, irinotecan and oxaliplatin were 2400, 150 and 75 mg/m2, respectively. Bolus 5-FU and leucovorin were omitted in all but 3 pts. Median PFS was 3.7 m (95% CI: 3.0-5.7) with mOS of 11.6 m (95% CI: 6.14-15.7). 16 pts (67%) experienced disease control (response to tx or stable disease). Grade 3 or 4 HT occurred in 11 pts (46%), and 9 (38%) were supported with granulocyte colony-stimulating factor at some point during tx. 6 pts (25%) required hospital admission for any toxicity, most commonly infection (3 pts), and 10 (42%) stopped FOLFIRINOX due to toxicity, most commonly fatigue (6 pts). Conclusions: In this single-center retrospective analysis of 24 unresectable PC pts age 75 or older given FOLFIRINOX, OS outcomes were similar to those reported by Conroy et al in the original trial which excluded pts older than 75. In our review, toxicities including incidences of grade 3 or 4 HT were similar to those reported in the initial study. These data indicate that the use of modified dosing FOLFIRINOX in advanced PC pts older than 75 appears to maintain similar efficacy and toxicity when compared to younger pts.

Comprehensive landscape of gene amplifications (amps) in tissue and circulating tumor DNA (ctDNA) in metastatic colorectal cancer (mCRC)

604

Background: Amps, as oncogenic and resistance drivers, have therapeutic implications, but unlike mutations, have been sparsely described in mCRC. Functional account is piecemeal due to vague definitions, limited data on co-occurring alterations and use of primary tissue samples nonrepresentative of tumor heterogeneity. Our aim was to define the amp landscape in mCRC using tissue and ctDNA sequencing. Methods: We performed systematic analyses of copy-number variation in 2 cohorts of mCRC patients (pts) [tissue (TC) (N = 1,134) and ctDNA (BC) (N = 3,218)] who had high sensitivity targeted sequencing with MSK-IMPACT (341-468 genes) or Guardant Health (70-73 genes) panel, respectively. For BC, plasma copy number was adjusted (ApCN) to account for variable tumor DNA shedding using max allele frequency and high amp (HAmp) was defined as > 4 copies (similar to predefined tissue cutoff). Results: 166 (15%) and 405 (13%) pts in TC and BC harbored amp in at least one of 18 genes assessed by both panels (Table). Amp prevalence for individual gene was similar in both cohorts ( r = 0.9; P < .01) with RTK amps ( EGFR, ERBB2, MET, FGFR1/2, PDGFRA) seen in 8% pts. Key RTK amps were enriched in RAS/BRAF wild type (RB WT) compared to mutant (RB MUT) (OR 3.5; P < .01) pts in both cohorts, in contrast to low prevalence RTK and non-RTK amps. Median ApCN was higher for RTKs in RB WT vs MUT cases ( ERBB2: 12 vs 5; P = .02). Using validated EGFRab exposure (EGFRi) ctDNA signature, we found that EGFRi pts had higher prevalence of EGFR, MET, BRAF, KRAS, PIK3CA and FGFR1 amps compared to EGFRab naïve pts. Conclusions: While individually uncommon, amps occur across key oncogenic pathways in mCRC and after adjusting for ctDNA shedding, are seen at similar prevalence in tissue and plasma. Amps in RTKs are seen in 10-12% of RB WT tumors, suggesting clinically relevant roles as oncogenic effectors and targets. After EGFRi, a number of amps emerge, including PIK3CA and FGFR1 amps, not previously implicated in acquired resistance. [Table: see text]

Plasma GH as a diagnostic and prognostic biomarker in HCC without cirrhosis

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Background: The association between the GH/IGF-1 axis and HCC was reported in patients (pt) with underlying cirrhosis. However, there is limited information among HCC pt without (w/o) cirrhosis. We herein investigated the role of GH as a circulating biomarker for HCC diagnosis and prognosis in pt w/o cirrhosis. Methods: Under IRB approval, we prospectively enrolled 1267 newly-diagnosed HCC pt in a case control study at the MD Anderson Cancer Center (2000-2015). Controls were healthy individuals (n = 1104). Plasma GH and AFP were measured 274 HCC pt w/o cirrhosis 200 healthy controls. IGF-1 was measured in 133 and 82 pt, respectively. We classified HCC pt into higher and lower GH values (cutoff for women, 3.7 µg/L; men, > 0.9 µg/L). Results: Most pt (74%) were male, with advanced BCLC staging (C-D, 74%) and 61% were older than 60y. Baseline GH was higher in HCC w/o cirrhosis (mean 3.3 µg/L) than controls (mean 0.4 µg/) (p < .001). ROC curve was plotted to assess diagnostic role. The AUC for AFP was 82.9 (p < .001); for GH 78.2 (p < .001). When only non-cirrhotic HCC pt with early stage (CLIP 0-2) and AFP < 20 ng/m were compared to controls, the GH/IGF-1 ratio had high prediction of early stage HCC - AUC 83 (95% CI 78-89%) (p < .0001). At a specificity of 90%, sensitivity of GH/IGF ratio was 67%. In addition, among HCC w/o cirrhosis, higher GH levels correlated with presence of vascular invasion (p < .001) and thrombosis (p = .004), tumor involvement of > 50% liver (p = .003), and more advanced BCLC (p < .001) and TNM staging (p < .001). Median overall survival (months) of HCC pt w/o cirrhosis with high GH levels was 13.1 (10.8-15.4) compared to 37.4 (19.8-55.1) of pt with lower plasma GH (p < .001). Multivariate cox-regression analysis identified high GH as an independent risk factor for mortality (HR = 1.8; 95% CI, 1.3-2.4; p < .001). Conclusions: Our study demonstrates the diagnostic and prognostic role of plasma GH in non-cirrhotic HCC and identifies the GH/IGF-1 ratio as a promising diagnostic marker for early stage HCC w/o cirrhosis and low AFP; this analysis excludes the confounding effect hepatocyte impaired function by presence of cirrhosis. Further studies are warranted to assess the causes of the observed differences.

Systematic review of three decades of clinical trials in metastatic colorectal cancer: Making lemonade out of lemons?

656

Background: Despite multiple trials of new agents in metastatic colorectal cancer (mCRC), long term outcomes remain poor. This study explores the changing trends in the design, interpretation and outcomes of phase III randomized controlled trials (RCT) in mCRC over time. Methods: Phase III RCTs of systemic therapy for mCRC with enrollment between 1986 and 2016 were identified through 4 electronic databases and grouped into 3 time periods (1986-1996 – T1; 1997-2006 – T2 & 2007-2016 – T3). Study selection, quality appraisal and data collection were performed by 2 independent investigators. Study characteristics, primary and secondary endpoints, and authors’ interpretation of results and conclusions were analyzed. Improvement in overall survival (OS) was the difference between experimental and control arms. A study was deemed positive if it met its end point, was recommended for further study or for adoption for clinical use (p ≤ 0.05 significant for all analyses). Results: One hundred fifty trials (T1=36, T2=62, T3=52) with 77494 patients (T1=12406, T2=39158, T3=25930) were included. Although 1st line therapy trials continued to be the most common across all T, the percentage (%) of trials evaluating 3rd line and beyond (T1=0, T2=3, T3=27) have increased significantly over time as have trials with targeted agents (T1=11, T2=34, T3=79). Although OS remains the most common primary end point, more trials in T2 & T3 have used progression-free survival instead (14 vs 47 & 44). The % of trials with negative results but interpreted as positive increased over time (T1=18; T2=42; T3=35). Across all T, the median improvement in OS (months, m) of these trials was significantly lower compared to the trials that met primary end point across all T (T1 = 0 vs 1.8 m, T2 = -0.1 vs 3.25, T3 = -0.25 vs 2.55). Conclusions: A significant shift has occurred over the past three decades in the design and interpretation of phase III trials in advanced CRC. Any interpretations of potential survival benefits from trials that have not met primary end point must be made with significant caution.

Prognostic value of genomic alterations (GA) on overall survival in appendiceal adenocarcinoma (AA)

554

Background: AA are extremely rare tumors, with potentially aggressive clinical behavior. The characterization of the molecular alterations of the disease is poorly described, as well as its association with clinical outcomes. The present study aims to evaluate the prognostic influence of GA on overall survival (OS) of AA patients (pts). Methods: We performed a retrospective study involving AA pts at MD Anderson Cancer Center between October 2012 and April 2017 who underwent next-generation sequencing (NGS) (at least 45 genes), using either tumor tissue specimens or peripheral blood for cell-free DNA (cfDNA). GA identified by NGS and clinicopathological variables were correlated with OS. Survival curves were performed by the Kaplan-Meier method and compared with log-rank test. Multivariate analysis of prognostic factors was performed by the Cox model. Results: A total of 78 pts were identified, of which 35 had died (45%) in a median follow-up time of 4.8 y. The majority of pts presented with stage IV disease (72%); 46% underwent cytoreductive surgery (CRS) + HIPEC. Tissue-based and cfDNA-based sequencing were performed on 73% and 23% of the pts, respectively, and 4% had both. The most frequent GA were KRAS (62%), TP53 (36%), GNAS (28%), SMAD4 (18%), PIK3CA (16%), and APC (15%). By univariate analysis, stage, tumor grade, and CRS + HIPEC demonstrated prognostic value (p < 0.05). Multivariate subset analysis of stage IV pts adjusting for age, tumor grade (TG), CRS + HIPEC, KRAS, GNAS, and p53, demonstrated that poorly differentiated tumors and a KRAS mutated tumor resulted in worse OS (HR: 12.1 and HR: 3.9, respectively, both with p < 0.05) and CRS + HIPEC resulted in an improved OS (HR: 0.32, p < 0.05). Conclusions: Our analysis indicates that TG and the presence of the KRAS mutation are poor prognostic factors in the OS of pts with AA. CRS + HIPEC offers survival advantage . Molecular characterization and prognostication of these rare tumors may help guide therapy. These findings need validation, thereby continued evaluation in a larger population and utilizing a wider molecular platform is ongoing.

Activity of EGFR inhibition in atypical (non-V600E) BRAF-mutated metastatic colorectal cancer

596

Background: Atypical BRAF mutations (a BRAF) represent a rare molecular subtype of metastatic colorectal cancer (mCRC), distinct from BRAFV600E (class I). Preclinical data categorizes a BRAF into class II (intermediate-high kinase activity without RAS dependency) and III (low kinase activity, RAS dependent), however the clinical impact regarding these functional classes is unknown. Methods: We retrospectively analyzed 2,084 mCRC patients (pts) at MD Anderson Cancer Center (MDACC) to identify a BRAF and BRAFV600E. Clinicopathologic features were compared by chi-square or fisher’s exact test. Overall survival (OS) calculated utilizing Kaplan-Meier method and log-rank test. Statistical tests were two-sided. Results: a BRAF occurred in 36 mCRC pts (1.7%; 95% CI 1.2-2.4): 22 class III, 10 class II, 4 unclassified. The most common class II and class III BRAF codons were 469 (60%) and 594 (59%), respectively . Median OS (mOS) for a BRAF mCRC was 39.4 months (mo), without difference between class III and II. 19/36 (53%) were left sided primary tumors and 24/36 (67%) were microsatellite stable. BRAFV600E occurred in 221 mCRC pts (10.6%; 95% CI 9.3-12.0) with a mOS of 21.0 mo. In contrast to BRAFV600E which is mutually exclusive with RAS mutations, 12 pts with a BRAF were RAS mutants (class III, 7/21 [33%], class II 5/10 [50%]). Among a BRAF RAS wt pts, 11 (50%) received anti-EGFR monoclonal antibodies (mAb) (class III 7/14 [50%], class II 3/5 [60%]). There were no responses, and only three pts (all class III) achieved stable disease as best response. Median time on therapy was 4 months. Class II RAS wt pts treated with anti-EGFR mAb had mOS of 31.7 mo versus 46.8 mo for those not exposed (HR 2.0; 95% CI 0.3-15.9). Class III RAS wt pts treated with anti-EGFR mAB had mOS of 44.2 mo versus 45.7 mo for those not treated (HR 0.80; 95% CI 0.2-2.6). Conclusions: a BRAF mCRC appear to manifest improved clinical outcomes as previously reported. Despite this, the efficacy of anti-EGFR therapy appears limited in class II and III patients. Future efforts are needed to establish the predictive impact of functional classes on anti-EGFR efficacy and to design novel therapeutic strategies for a BRAF mCRC.

IGF-Child-Pugh score as a predictor of treatment outcome in Child-Pugh A, advanced hepatocellular carcinoma patients undergoing sorafenib therapy

223

Background: Sorafenib is the first systemic therapy approved for advanced HCC treatment; with no accurate tool available to help predict survival and treatment outcome and to guide therapy decisions. Our novel blood-based IGF-Child-Pugh (CP) score comprises levels of IGF-1, bilirubin, INR, and albumin. IGF-CP score significantly improved the prediction of HCC survival in our recently published studies. The current prospective study aimed to compare the overall survival (OS) and progression free survival (PFS) of 101 patients with CP-A HCC treated with sorafenib whose score is reclassified as IGF-A (AA) to that of patients whose score is reclassified as IGF-B/C (AB/AC). Methods: Between 2014 and 2018, after the approval of the institutional review boards and signing written informed consent, a total of 101 patients with HCC, CP-A were prospectively enrolled and started on sorafenib and followed until progression or death. Results: Sixty-three patients were evaluable. Patients who were reclassified by the IGF-CTP scoring system were better stratified by their new risk groups. Forty-two of patients were classified as IGF-CTP-A and had median PFS of 4.87 months (95% CI=2.3 to 6.84), and median OS of 15.43 (95% CI = 12.04 to 31.18 months), whereas 21 patients were reclassified as intermediate risk (IGF-CTP-B) and had significantly shorter OS of 7.6 months (p-value<0.0001) and shorter PFS of 2.86 months (p-value=0.0021). Conclusions: The results of this study confirms our biologically driven hypothesis that: among HCC patients with “old CP-A” class treated with sorafenib, some will be reclassified as “new CP-B/C” will have poorer prognosis in terms of shorter OS and PFS. Thus, our study provides an objective non-invasive strategy to better predict the outcome in HCC patients undergoing systemic therapy. Future validation of our IGF score may lead to adopting it as a stratification tool in trials to predict HCC outcome and guide therapy decision in routine practice. [Table: see text]

Quantifying the evolution of tumor architecture using serial circulating tumor DNA

600

Background: There is limited data regarding changes in the genomic landscape in individual patients over time as serial tissue biopsy has risk and is of uncertain clinical benefit. The advent of circulating tumor DNA (ctDNA) allows for safe and repeated molecular sampling with the potential to investigate evolution of tumor architecture over the disease course. Methods: From 5/15 to 12/17, 116 patients with metastatic CRC had between three to 12 blood specimens taken over the treatment course. Plasma was tested using targeted NGS assay (Guardant360, Guardant Health, 68 gene). To account for variations in the amount of ctDNA in serial samples, a window of evaluable allele frequency was established for each patient as the fold change between the max allele frequency (mAF) and limit of detection for serial samples with the lowest mAF. Mutations not falling within this window were excluded from analysis. Substantial treatment induced selective pressure (SP) was defined as a decrease in the mutant mAF of > 50% in patients with at least an initial mAF of 1%. Results: 116 patients with a total of 317 serial blood samples were evaluable after accounting for ctDNA variations over time. Specimens were collected a median of 12 months apart, with a median of three specimens per patient. Thirteen patients (11%) did not have any changes in mutations on serial sampling, however the remainder of patients gained an average of 1.1 mutations per time point (mut/tp), and lost 1.0 mut/tp. 31% of patients demonstrated evidence of substantial treatment-induced SP. These patients were more likely to demonstrate a change in clonal architecture of the tumor (46% greater rate than those without SP, P = 0.04), predominantly through gain of new clones. In contrast, clonal hematopoiesis alterations that may be induced by chemotherapy, such as JAK2V617F, were neither gained or lost. Conclusions: After correction for variations over time in the total amount of ctDNA in circulation, we identify numerous changes in tumor architecture with serial sampling. For the first time in colorectal cancer we demonstrate that when treatment-induced SP is applied the rate of tumor evolution is increased, demonstrating potential value of monitoring changes in tumor architecture over the disease course.

An open-label phase Ib/2 trial of TRC105 plus sorafenib in patients with advanced/metastatic hepatocellular carcinoma (HCC) (NCT01806064)

268

Background: TRC105, an endoglin antibody, potentiates the activity of sorafenib (S) in preclinical HCC models, and TRC105 + S demonstrated a 33% partial response rate (5/15 pts) by RECIST, at RP2D doses of TRC105 in HCC pts ( Clin Can Res 2017). Adverse events characteristic of each drug were not increased in frequency or severity when the two drugs were administered concurrently. Methods: P1: Compare wkly TRC105 dosing vs four wkly doses followed by every other wkly dosing + S 800 mg daily. P2: Four objective responses are required in 21 pts to reject the null hypothesis that the true response rate probability is < 5% with an alpha level of 0.1 and 80% power. Key inclusion criteria: disease not amendable to surgical or local therapies, ECOG ≤ 1; Child-Pugh A or B (7 points) classification. Results: Thirteen pts were enrolled in phase 1b at TRC105 10 mg/kg wkly for four doses and 15 mg/kg every other week thereafter + S. Mean serum levels of TRC105 exceeded the target conc. following 4 wkly doses of TRC105 at 10 mg/kg (mean = 34 µg/ml, range BLOQ-80). Mean trough conc. decreased following every other week dosing (mean = 13 µg/ml, range BLOQ-31), resulting in infusion reactions or a continued requirement for premedication. Therefore, wkly dosing of TRC105 at 10 mg/kg is the recommended Phase 2 dose. ADA were detected in 10 of 14 pts and correlated with lower than expected PK conc. Common TRC105 related AEs included ≤ G2 epistaxis, ≤ G2 fatigue and ≤ G2 headache. Common S related AEs included ≤ G3 fatigue, ≤ G3 hand foot syndrome and ≤G2 epistaxis. A total of 3 out of 14 evaluable patients (21%) enrolled in phase 1 and 2 achieved durable PR, 2 of these ongoing at week 45 and 17. Conclusions: TRC105 dosed at 10 mg/kg wkly was required to achieve target conc. due to higher clearance in HCC pts, which may have been influenced by a higher rate of ADA compared to studies of TRC105 in other tumor types. The combination of TRC105 + S demonstrated encouraging signs of activity, including durable PR in 2/9 evaluable pts in Phase 1b and 1/5 pts thus far in Phase 2. An additional 16 pts will be enrolled at the RP2D to assess the primary endpoint of ORR by RECIST. Clinical trial information: NCT01806064.

Retrospective Analysis of Taxane-Based Therapy in Small Bowel Adenocarcinoma

Currently, treatment of small bowel adenocarcinoma (SBA) mirrors that of colorectal cancer (CRC). Recent genomic data have demonstrated SBA to be a genetically unique entity, suggesting that therapies not traditionally utilized in CRC should be explored. In order to further characterize the activity of taxanes in this rare cancer, we completed a single-center retrospective study. Twenty patients were found to have been treated with taxane-based regimens (monotherapy in 3, combination therapy in 17). Median time to progression was 3.8 months (95% confidence interval [CI] 2.9-4.6), and median overall survival was 10.7 months (95% CI: 3.1-18.3). The results of this study demonstrate clinical activity from taxane-based therapy in advanced SBA and support further clinical trial investigation.

FBXW7 missense mutation: a novel negative prognostic factor in metastatic colorectal adenocarcinoma

Background

FBXW7 functions as a ubiquitin ligase tagging multiple dominant oncogenic proteins and commonly mutates in colorectal cancer. Data suggest missense mutations lead to greater loss of FBXW7 function than other gene aberrations do. However, the clinicopathologic factors and outcomes associated with FBXW7 missense mutations in metastatic colorectal cancer (mCRC) have not been described.

Methods

Data were obtained from mCRC patients whose tumors were evaluated by next-generation sequencing for hotspot mutations at The University of Texas MD Anderson Cancer Center. Alterations in FBXW7 were identified, and their associations with clinicopathologic features and overall survival (OS) were evaluated.

Results

Of 855 mCRC patients, 571 had data on FBXW7 status; 43 (7.5%) had FBXW7 mutations, including 37 with missense mutations. R465C mutations in exon 9 were the most common missense mutations (18.6%). PIK3CA mutations were associated with FBXW7 missense mutations (p=0.012). On univariate analysis, patients with FBXW7 missense mutations had significantly worse OS (median 28.7 mo) than those with wild-type FBXW7 (median 46.6 mo; p=0.003). On multivariate analysis including other known prognostic factors such as BRAF mutations, FBXW7 missense mutations were the strongest negative prognostic factor for OS (hazard ratio 2.0; p=0.003).

Conclusions

In the largest clinical dataset of mCRC to date, FBXW7 missense mutations showed a strong negative prognostic association.

Comprehensive genomic profiling of appendiceal adenocarcinoma

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Background: Appendiceal adenocarcinomas (AAs) are orphan tumors. Little is known about their molecular profile limiting understanding of their biology and development of novel targeted therapies. The purpose of this study was to delineate the molecular landscape of AAs. Methods: We performed a retrospective review of AAs patients (pts) who were evaluated at MD Anderson Cancer Center between October 2012 and April 2017 and underwent next-generation sequencing (NGS) with internal or external assays (at least 45 genes) using either tumor tissue specimens or peripheral blood for circulating cell-free DNA (cfDNA). The primary outcome was to assess the prevalence of genomic alterations (GAs) in AAs. We then performed comparative exploratory analyses of GAs using TCGA colorectal cancer (CRC) sequencing. Results: A total of 78 patients were identified of which 57 (73%) and 18 (23%) underwent tissue based and ctDNA based sequencing, respectively (3 cases had both). At least 1 GA was found in 61 (78%) of AA specimens, with a mean (SD) of 2.8 (1.6) GAs per case. Of these 44 (72%) had ≥ 2 GAs and 31 (51%) had ≥ 3 GAs. The most frequent GAs were KRAS (38 [62%]), TP53 (22 [36%]), GNAS (17 [28%]), SMAD4 (11 [18%]), PIK3CA (10 [16%]), APC (9 [15%]), ATM (8 [13%]), BRAF (5 [8%]), KIT (5 [8%]), NRAS (3 [5%]) and MET (3 [5%]). GNAS mutations frequently co-occurred with KRAS mutations (42% v 5%, OR 14.3, P < 0.001). No GA was associated with grade, mucinous histology or overall survival (OS). Besides these mutations, we also found unusual cases with targetable mutations such as ALK, EGFR, MET, IDH1 and ERBB2. In our comparative analyses, mutations in KRAS (p = 0.009), TP53 (p = 0.020), GNAS (p < 0.001) and APC (p < 0.001) genes were significantly different from CRC whereas there was no difference in prevalence of PIK3CA, SMAD4 and ATM genes. Conclusions: To date, our analysis of one of the largest cohorts of AAs, demonstrate a majority of AAs harbor at least 1 GAs. Although treatment paradigms in AAs are extrapolated from CRC, the molecular profile of these tumors differs significantly. Molecular characterization of these rare tumors is a necessary first step towards discovery of opportunities for use of targeted therapies in these patients.

Malignant peritoneal mesothelioma: Clinicopathological features, prognostic factors, and survival outcomes

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Background: Peritoneal mesothelioma (PeM) is an orphan disease with approximately 300-400 cases diagnosed in the United States each year. Due to its rarity, data on its presentation and prognostic factors is limited. The purpose of this study was to investigate the clinicopathological profile and outcome of Malignant PeM (MPeM). Methods: We retrospectively reviewed 128 PeM patients (pts) seen at UTMDACC (2011 - 2017) comprised of 111 MPeM and 17 variants (VPeM) [9 well-differentiated papillary and 8 multicystic]. Kaplan-Meier method was used to estimate median overall survival (mOS) and compared with log-rank tests. Results: Median age at diagnosis was 57 yrs. with a higher proportion of women (61%). The mOS for MPeM was significantly shorter than VPeM (HR 3.7, 95% CI: 1.6 – 8.4, P = 0.002). Among pts with MPeM, median age at diagnosis was 56 yrs. and 58% were women. Only 22% had prior exposure to asbestos. Epithelioid subtype was seen in 94 (85%) pts. Calretinin and WT-1 IHC were positive in 98% and 96% of cases. BerEP4 and MOC-31 IHC were negative in 90% and 84% of cases. After median follow-up of 31 months (m), the mOS for MPeM cohort was 78 m. In univariate analysis, age, prior asbestos exposure, ECOG PS, histologic subtype, CA125, neutrophil-lymphocyte ratio (NLR) and cytoreductive surgery (CRS) were found to be associated with OS. In multivariate analyses, age ≥ 65 years (HR 4.5, 95% CI: 1.3 - 15.2, P = 0.02), prior asbestos exposure (HR 4.1, 95% CI: 1.1 – 15.6, P = 0.04), poor PS (ECOG 2/3) (HR 8.9, 95% CI: 1.7 – 47.7, P = 0.01), elevated CA125 ( > 3X upper limit of normal) (HR 4.5, 95% CI: 1.3 – 15.5, P = 0.02), and high NLR (HR 3.8, 95% CI: 1.1 – 12.6, P = 0.03) were found to be independently associated with poor OS. A total of 50 (45%) pts underwent CRS and among these the completion of cytoreduction score (CCS) was strongly associated with OS (mOS: 201 m, 53 m and 36 m for CCS 0, 1, 2/3, respectively, P = 0.005). Conclusions: MPeM is associated with poor survival outcomes. Prognostic factors include age, history of asbestos exposure, CA-125 level, NLR, and PS. CRS with CCS 0 results in favorable survival. Further understanding of molecular genetics is warranted to improve prognostication and outcomes.

Impact of microsatellite instability (MSI) on tumor clonal evolution in metastatic colorectal cancer (mCRC)

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Background: For mCRC, the contribution of clinical and pathologic factors to concordance between formalin-fixed, paraffin-embedded (FFPE) tissue-based and ctDNA-based mutation profiling remains unclear. MSI is hypothesized to confer a higher rate of somatic alteration resulting in clonal evolution over time compared to microsatellite stable (MSS) patients, but this has not been previously confirmed. Methods: All mCRC patients were consented for a prospective genomic matching protocol (Assessment of Targeted Therapies Against Colorectal Cancer [ATTACC]) using CLIA-certified platforms. Archived tumor DNA from primary or metastatic tissue was sequenced on a 46- or 50-gene panel (Ion Torrent). Paired ctDNA samples were isolated from blood and sequenced with an ultra high-sensitivity assay (Guardant360). Mutation data were normalized by excluding genomic regions not covered on both platforms and were filtered to remove germline or synonymous variants. Results: An initial cohort of 139 patients was included in our analyses, with a median of two lines of intervening chemotherapy between FFPE and plasma DNA collection; 6 (4.3%) of the patients had MSI (MSI-H) mCRC. We detected 472 total mutations in either tissue or ctDNA, with a global concordance rate of 34.5%. Global concordance was not associated with tissue source, nor treatment with specific standard cytotoxic and/or biologic agents. Mutations detected in MSI-H CRC showed significantly greater discordance compared to MSS CRC (OR = 2.5, p = 0.025). This finding was validated using an independent cohort of 17 MSI-H mCRC patients (OR = 2.78, p = 0.00015). Among recurrently altered genes, we found that MSI-H cases were significantly more likely to have gained new TP53 mutations (OR = 8.17, p = 0.001) and to have lost PIK3CA mutations (OR = 8.04, p = 0.036) in ctDNA compared to MSS cases. Conclusions: MSI correlates with discordance between tissue DNA and ctDNA-based mutation profiling, which suggests that MSI-H CRC undergoes distinct patterns of clonal evolution including acquisition of new TP53 mutations. This may have implications for targeted and immunologic therapies in this unique population, and suggests a utility for repeated molecular testing.

Serial monitoring of ctDNA to highlight mutation profiles in colorectal cancer

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Background: Circulating tumor DNA (ctDNA) represents an ideal platform to obtain the most current genomic profile of a patient’s tumor. We aimed to investigate how stable these profiles remain during serial ctDNA assays in metastatic colorectal cancer (mCRC). Methods: In 77 patients (pts) with mCRC and serial Guardant360 assays with a detectable mutation (mt), we compared mt stability by assessing whether variants were gained/lost between serial assays and changes in relative mutant allele frequency (rMAF). rMAF of a mt was defined as (mt allele frequency / mt present at the maximum allele frequency in that assay). rMAF results were normalized to detected ctDNA concentration changes between assays to ensure changes in rMAF were not due to changes in ctDNA concentration. MAPK pathway mutations were defined as RAS, BRAF, EGFR, KIT, or MET mutations. Results: Of 77 pts, 64 (83%) had 2 serial assays and 13 (16.9%) had 3 or 4 assays performed. Serial assays occurred an average of 138 days apart (+/- SD of 111 days). Only 13/77 (17%) pts had no change in the number of mts detected between assays. A new mt was detected in 42/77 (55%) pts, while 43/77 (56%) lost a previously detected mt. Of 52 mts detected in patients with > 2 assays, 16 (31%) were gained and subsequently lost. After controlling for ctDNA concentration, mts were equally likely to have an increasing (129/308 – 42%) or decreasing (150/308 – 49%) allele frequency. Potentially clinically relevant MAPK variants were gained/lost in 29% of patients; though MAPK mts developed in a large number of pts (16/77 – 21%), many pts also lost MAPK mts (9/77 – 12%), showing ongoing subclonal dynamics. Median time between assays did not differ between pts with gain/lost mts or stable mt profiles (P = 0.73), however mt rMAF shift of > 25% was more common if assays were > 90 days apart (OR 4.3, P < 0.0001). Conclusions: Serial ctDNA assays demonstrate ongoing mutational changes in mCRC, with emergence/disappearance of MAPK variants being more common than expansion of a pre-existing clone. Our results suggest repeated sampling may be important to optimize selection of targeted therapies at each regimen alteration.

An open label phase 1b/2 trial of TRC105 and sorafenib in patient with advanced/metastatic hepatocellular carcinoma (HCC) (NCT01806064)

301

Background: Endoglin plays a critical role in angiogenesis and is implicated in resistance to VEGF inhibition. TRC105, an endoglin antibody potentiates anti-tumor activity of sorafenib (S) in preclinical HCC models. The combination of TRC105 and S demonstrated encouraging evidence of activity, including a 33% partial response rate (5/15 pts) by RECIST, at RP2D doses of TRC105 in HCC ( Clin Can Res 2017). Adverse events characteristic of each drug were not increased in frequency or severity when the two drugs were administered concurrently, and most commonly included epistaxis, fatigue, headache and anemia. Methods: Following dose escalation, 21 pts will be enrolled at the RP2D. Four objective responses are required to reject the null hypothesis that the true response rate probability is < 5% with an alpha level of 0.1 and 80% power. Secondary endpoints: DR, PFS, frequency and severity of AEs, PK, immunogenicity, angiogenic biomarkers. Key inclusion criteria: disease not amendable to surgical or local therapies, ECOG ≤ 1; Child-Pugh A or B (7 points) classification. Results: Four pts have been enrolled in phase 1b at TRC105 10 mg/kg (n=4) weekly for four doses and 15 mg/kg every other week thereafter + S 800 mg daily without DLT. One of 3 evaluable pts achieved PR (41% reduction), ongoing at month 4. Serum levels of TRC105 exceeded the target concentration following 4 weekly doses of TRC105 at 10 mg/kg (mean = 59 µg/ml, range 43-80). Mean trough concentration decreased following every other week dosing (mean = 21 µg/ml, range 17-31). Common TRC105 related AEs included ≤ G2 epistaxis and G1 headache. Common S related AEs included G3 hand foot syndrome, ≤G3 periodontal disease, G2 hypertension, ≤G2 increased lipase, ≤G2 fatigue and G1 epistaxis. Conclusions: TRC105 dosed by a hybrid schedule of 10 mg/kg weekly for four doses followed by every other week dosing at 15 mg/kg was tolerable and did not potentiate the toxicity of S. The combination of TRC105 + S demonstrated additional signs of activity, including a PR in 1/3 evaluable pts. 21 pts will be enrolled at the RP2D to assess the primary endpoint of ORR by RECIST. Clinical trial information: NCT01806064.