Baseline ctDNA gene alterations as a biomarker of survival after panitumumab and chemotherapy in metastatic colorectal cancer

Certain genetic alterations and right-sided primary tumor location are associated with resistance to anti-epidermal growth factor (EGFR) treatment in metastatic colorectal cancer (mCRC). The phase 3 PARADIGM trial (n = 802) demonstrated longer overall survival with first-line anti-EGFR (panitumumab) versus antivascular endothelial growth factor (bevacizumab) plus modified FOLFOX6 in patients with RAS wild-type mCRC with left-sided primary tumors. This prespecified exploratory biomarker analysis of PARADIGM (n = 733) evaluated the association between circulating tumor DNA (ctDNA) gene alterations and efficacy outcomes, focusing on a broad panel of gene alterations associated with resistance to EGFR inhibition, including KRAS, NRAS, PTEN and extracellular domain EGFR mutations, HER2 and MET amplifications, and ALK, RET and NTRK1 fusions. Overall survival was prolonged with panitumumab plus modified FOLFOX6 versus bevacizumab plus modified FOLFOX6 in patients with ctDNA that lacked gene alterations in the panel (that is, negative hyperselected; median in the overall population: 40.7 versus 34.4 months; hazard ratio, 0.76; 95% confidence interval, 0.62-0.92) but was similar or inferior with panitumumab in patients with ctDNA that contained any gene alteration in the panel (19.2 versus 22.2 months; hazard ratio, 1.13; 95% confidence interval, 0.83-1.53), regardless of tumor sidedness. Negative hyperselection using ctDNA may guide optimal treatment selection in patients with mCRC. ClinicalTrials.gov registrations: NCT02394834 and NCT02394795 .

Panitumumab vs Bevacizumab Added to Standard First-line Chemotherapy and Overall Survival Among Patients With RAS Wild-type, Left-Sided Metastatic Colorectal Cancer: A Randomized Clinical Trial

Importance

For patients with RAS wild-type metastatic colorectal cancer, adding anti-epidermal growth factor receptor (anti-EGFR) or anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibodies to first-line doublet chemotherapy is routine, but the optimal targeted therapy has not been defined.

Objective

To evaluate the effect of adding panitumumab (an anti-EGFR monoclonal antibody) vs bevacizumab (an anti-VEGF monoclonal antibody) to standard first-line chemotherapy for treatment of RAS wild-type, left-sided, metastatic colorectal cancer.

Design, Setting, and Participants

Randomized, open-label, phase 3 clinical trial at 197 sites in Japan in May 2015-January 2022 among 823 patients with chemotherapy-naive RAS wild-type, unresectable metastatic colorectal cancer (final follow-up, January 14, 2022).

Interventions

Panitumumab (n = 411) or bevacizumab (n = 412) plus modified fluorouracil, l-leucovorin, and oxaliplatin (mFOLFOX6) every 14 days.

Main Outcomes and Measures

The primary end point, overall survival, was tested first in participants with left-sided tumors, then in the overall population. Secondary end points were progression-free survival, response rate, duration of response, and curative (defined as R0 status) resection rate.

Results

In the as-treated population (n = 802; median age, 66 years; 282 [35.2%] women), 604 (75.3%) had left-sided tumors. Median follow-up was 61 months. Median overall survival was 37.9 months with panitumumab vs 34.3 months with bevacizumab in participants with left-sided tumors (hazard ratio [HR] for death, 0.82; 95.798% CI, 0.68-0.99; P = .03) and 36.2 vs 31.3 months, respectively, in the overall population (HR, 0.84; 95% CI, 0.72-0.98; P = .03). Median progression-free survival for panitumumab vs bevacizumab was 13.1 vs 11.9 months, respectively, for those with left-sided tumors (HR, 1.00; 95% CI, 0.83-1.20) and 12.2 vs 11.4 months overall (HR, 1.05; 95% CI, 0.90-1.24). Response rates with panitumumab vs bevacizumab were 80.2% vs 68.6%, respectively, for left-sided tumors (difference, 11.2%; 95% CI, 4.4%-17.9%) and 74.9% vs 67.3% overall (difference, 7.7%; 95% CI, 1.5%-13.8%). Median duration of response with panitumumab vs bevacizumab was 13.1 vs 11.2 months for left-sided tumors (HR, 0.86; 95% CI, 0.70-1.10) and 11.9 vs 10.7 months overall (HR, 0.89; 95% CI, 0.74-1.06). Curative resection rates with panitumumab vs bevacizumab were 18.3% vs 11.6% for left-sided tumors; (difference, 6.6%; 95% CI, 1.0%-12.3%) and 16.5% vs 10.9% overall (difference, 5.6%; 95% CI, 1.0%-10.3%). Common treatment-emergent adverse events were acneiform rash (panitumumab: 74.8%; bevacizumab: 3.2%), peripheral sensory neuropathy (panitumumab: 70.8%; bevacizumab: 73.7%), and stomatitis (panitumumab: 61.6%; bevacizumab: 40.5%).

Conclusions and Relevance

Among patients with RAS wild-type metastatic colorectal cancer, adding panitumumab, compared with bevacizumab, to standard first-line chemotherapy significantly improved overall survival in those with left-sided tumors and in the overall population.

Trial Registration

ClinicalTrials.gov Identifier: NCT02394795.

Panitumumab (PAN) plus mFOLFOX6 versus bevacizumab (BEV) plus mFOLFOX6 as first-line treatment in patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC): Results from the phase 3 PARADIGM trial

LBA1

Background: PARADIGM is the first prospective trial to test the superiority of PAN vs. BEV in combination with standard doublet first-line chemotherapy for patients (pts) with RAS WT mCRC and left-sided primary tumors. Methods: This open-label, multicenter trial in Japan (NCT02394795) randomly selected pts with chemotherapy-naive RAS WT mCRC to PAN + mFOLFOX6 or BEV + mFOLFOX6. Overall survival (OS) as primary endpoint was hierarchically tested in patients with left-sided tumors, followed by those in the full-analysis set (FAS) population. Key secondary endpoints included progression-free survival (PFS), response rate (RR), and curative resection (R0) rate. Results: From May 2015 to June 2017, 823 pts were randomized; 12 did not receive protocol treatment and 9 were excluded due to major deviation of inclusion criteria. A total of 400 pts received PAN and 402 pts received BEV as FAS; 312 and 292 pts had left-sided primary tumors, respectively. OS was analyzed after 448 OS events in left-sided pts with a median follow-up of 61 months. PAN significantly improved OS vs. BEV in both populations: left-sided (HR, 0.82; 95.798% CI, 0.68-0.99, p = .031, which crossed the boundary of significance [0.042]), and FAS (HR, 0.84; 95% CI, 0.72-0.98; p = .030, with < 0.05 as the boundary). Although PFS was comparable between treatment groups, RR and R0 resection rates were higher with PAN compared with BEV (Table). HR for OS in the right-sided population was 1.09. No new safety signal was observed. Conclusions: PAN significantly improved OS vs. BEV in combination with mFOLFOX6 in pts with RAS WT and left-sided mCRC, establishing a standard first-line combination regimen for this population. Clinical trial information: NCT02394795. [Table: see text]

PARADIGM study: A multicenter, randomized, phase III study of mFOLFOX6 plus panitumumab or bevacizumab as first-line treatment in patients with RAS (KRAS/NRAS) wild-type metastatic colorectal cancer

85

Background: The optimal choice of monoclonal antibodies (mAbs) for first-line treatment in patients (pts) with RAS ( KRAS/NRAS) wild-type metastatic colorectal cancer (mCRC) remains controversial. The meta-analyses of subgroup analyses in phase III studies of pts with KRAS exon 2 wild-type mCRC suggested a longer overall survival (OS) with an anti-EGFR mAb over bevacizumab in pts with RAS wild-type mCRC or with left-sided primary tumors. However, there has been no prospective study comparing the two mAbs in these pt populations. This randomized phase III study was originally designed to demonstrate the superiority of panitumumab versus bevacizumab, both in combination with mFOLFOX6, for RAS wild-type mCRC, but we have revised the protocol to analyze efficacy in pts with a left-sided primary tumor as the primary (final) analysis. Methods: Eligible pts are aged 20-79 years with histologically/cytologically confirmed RAS wild-type chemotherapy-naive mCRC, and ECOG performance status 0-1. Between May 29, 2015 and Jun 8, 2017, 823 pts were randomized 1:1 to panitumumab plus mFOLFOX6 or bevacizumab plus mFOLFOX6 by the minimization method and the randomisation was stratified by institution, age (20-64 vs. 65-79 years), and liver metastases (present vs. absent). The primary analysis was revised to adopt a hierarchical testing procedure; we first compare OS between the two arms in left-sided primary tumor population, and only if there is statistically significant difference, then ITT population analysis will be performed. In this revised plan, the expected number of deaths is 420 in the left-sided population to provide 80% power to detect an OS hazard ratio of 0.74 at a one-sided significance level of 0.02101 determined on the alpha spending function approach after one interim analysis. A large-scale exploratory biomarker substudy to identify potential biomarker candidates using tumor tissue and circulating tumor DNA is also underway (Clinical trial no.: NCT02394834). The data cut off for the primary analysis is expected to be during 1Q 2021. Results: Results are expected in 2021. Conclusions: Results are expected in 2021. Clinical trial information: NCT0239475.

Abstract 1974: Clonal and subclonal mutational landscapes in circulating tumor DNA in metastatic colorectal cancer: An exploratory analysis from the phase III PARADIGM study

Introduction: We performed an exploratory analysis of circulating tumor DNA (ctDNA) in patients (pts) with RAS wild-type (WT) chemotherapy-naïve stage IV metastatic colorectal cancer (mCRC) from the ongoing phase III PARADIGM study (NCT02394834). The clonal and subclonal mutational landscapes of RAS WT pts were analyzed using a mCRC-focused custom ctDNA sequencing panel.

Methods: Randomized pts (1:1) received mFOLFOX6 plus either panitumumab or bevacizumab. Pre-treatment plasma samples (DNA yield &gt;10ng/mL and &gt;10nM) were sequenced using the custom ctDNA panel (PlasmaSELECTTM-R 91, PGDx) to detect mCRC mutations, amplifications, and rearrangements in 90, 26, and 3 genes, respectively, as well as microsatellite instability (MSI), in 250kb targeted regions using stringent quality criteria. Pre-treatment archival tissue samples from 590 pts were analyzed by the Broad Institute Solid Tumor panel, which covered 1,072 genes with 7.3Mb targeted regions.

Results: Between May 29, 2015 and June 8, 2017, 823 pts were enrolled across 197 sites. Plasma samples were collected from 756 pts, with 747 (98.8%) samples meeting the quality criteria. The average total and distinct sequencing coverages were 34,200 and 5,865, respectively, with 49.1% of bases mapping to regions of interest. Mutation frequencies in ctDNA were generally consistent with those observed in RAS-WT TCGA CRC and rectal cancers (n=283), except for TET2 and DNMT3A potentially due to clonal hematopoiesis. Mutations in BRAF, APC, CTNNB1, PTEN, PIK3CA, and MSI-status observed in ctDNA were significantly different between left and right-sided tumors, consistent with known differences in tumor sidedness. In the 747 plasma samples, 4,072 mutations were observed; 1,871 had a mutant allele frequency (MAF) &lt;25% of the highest MAF in each sample (defined as subclonal) and 2,201 had a MAF above this threshold (defined as clonal). Clonal mutations were 77.5% concordant with mutations in corresponding tissue samples. Subclonal mutations showed 17.3% concordance between tissue and plasma, suggesting that tumor heterogeneity may result in subclonal mutations in ctDNA. Although pts with KRAS/NRAS mutations (G12, G13, A59, Q61, K117, A146) in archival FFPE tissue were not eligible for this study, 38 RAS mutations (58% subclonal) were observed in ctDNA of 32 pts, suggesting that sub-populations of tumor cells may have KRAS mutations in these cases. Patient-level subclonality analyses suggested that the fraction of subclonal mutations were higher in pts with metastases in ≥2 organ sites.

Conclusion: The validated ultra-deep plasma sequencing panel was concordant with tissue sequencing and detected tumor heterogeneity. The PARADIGM study will report the efficacy of anti-EGFR/VEGF therapies; post-treatment collection of ctDNA is ongoing. The relationship between therapeutic effects and clonal and subclonal mutational landscapes will be examined in the future. Funded by Takeda Pharmaceutical Company Limited, Tokyo, Japan. ClinicalTrial.gov number: NCT02394834

Citation Format: Katsuya Tsuchihara, Riu Yamashita, Takayuki Yoshino, Kohei Shitara, Jun Watanabe, Hirofumi Yasui, Hisatsugu Ohori, Manabu Shiozawa, Kentaro Yamazaki, Eiji Oki, Takeo Sato, Takeshi Naitoh, Yoshito Komatsu, Takeshi Kato, Kazunori Yamanaka, Ikuo Mori, Masamitsu Hihara, Junpei Soeda, Takeharu Yamanaka, Kiwamu Akagi, Atsushi Ochiai, Kei Muro, Victor E. Velculescu, Hiroyuki Uetake. Clonal and subclonal mutational landscapes in circulating tumor DNA in metastatic colorectal cancer: An exploratory analysis from the phase III PARADIGM study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1974.

Abstract CT164: Circulating tumor DNA analysis for predictive and prognostic factors in patients with metastatic colorectal cancer: An exploratory analysis from the phase III PARADIGM study

Introduction Circulating tumor DNA (ctDNA) is an emerging biomarker used to track disease progression and treatment response. To investigate mechanisms of resistance to panitumumab and bevacizumab, we performed an exploratory analysis of ctDNA from patients (pts) with metastatic colorectal cancer (mCRC) in the ongoing phase III PARADIGM study (NCT02394834). We present an initial feasibility report of this analysis using a next generation sequencing-based platform.

Methods Pts with chemotherapy-naïve RAS wild-type mCRC were randomized 1:1 to receive mFOLFOX6 plus either panitumumab or bevacizumab. Plasma samples were taken pre- and post-treatment. Samples with a DNA yield of &gt;10ng/mL and &gt;10nM (assessed using an Agilent 2100 Bioanalyzer) were sequenced using an mCRC-focused ctDNA sequencing panel (PlasmaSELECTTM-R 91, PGDx) to detect mutations, amplifications, and rearrangements for 90, 26, and 3 genes, respectively, and microsatellite instability with 250kb targeted regions. Selected genes covered known pathways and functions related to CRC and sensitivity/resistance to anti-EGFR/VEGF therapies. Sequenced DNA required &gt;12,500x average coverage, &gt;15% mapping to regions of interest, and &gt;75x average high quality distinct coverage; analytical validity of the panel was established using standard samples. Pre-treatment archival tissue samples were collected and analyzed by the Broad Institute Solid Tumor panel, which covers 1,072 genes with 7.3Mb targeted regions.

Results Between May 29th 2015 and June 8th 2017, 823 pts were enrolled at 197 sites. Pre-treatment plasma samples and tissue samples were collected from 756 pts (92%); &gt;99.9% of plasma samples met the pre-specified quality criteria (QC). At the time of this feasibility analysis, 337 pre-treatment plasma samples that fulfilled the QC had been sequenced. In sensitivity validation, 92% of mutations were detected at the 0.1% mutant allele fraction (MAF) and 100% were detected at the &gt;0.5% MAF with &gt;99.9% specificity. In total, 25 tissue- and plasma-matched samples and 5 plasma samples without matched tissue samples were analyzed. Using individual mutations in tissue DNA as the denominator, genetic concordance was 100% (3/3) with BRAF and 70% (7/10) with TP53 between plasma and tissue samples for common TCGA mutations. Mechanisms of resistance to each therapy will be assessed by sub-clone analysis of pre- and post-treatment samples using the validated ultra-deep ctDNA sequencing panel. Collection of post-treatment samples is ongoing.

Conclusion Initial data confirms the analytical feasibility of this method and supports the use of ctDNA to track clonal evolution. Further analyses are warranted in all pts to explore the underlying mechanisms of response to treatment with anti-EGFR/VEGF therapies.

Citation Format: Katsuya Tsuchihara, Kei Muro, Takayuki Yoshino, Kohei Shitara, Kentaro Yamazaki, Mitsuyoshi Ota, Eiji Oki, Takeo Sato, Takeshi Naitoh, Yoshito Komatsu, Takeshi Kato, Kazunori Yamanaka, Ikuo Mori, Masamitsu Hihara, Jumpei Soeda, Sunita Badola, Hyunjin Shin, Takeharu Yamanaka, Kiwamu Akagi, Atsushi Ochiai, Hiroyuki Uetake. Circulating tumor DNA analysis for predictive and prognostic factors in patients with metastatic colorectal cancer: An exploratory analysis from the phase III PARADIGM study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT164.

PARADIGM study: A multicenter, randomized, phase III study of 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) plus panitumumab or bevacizumab as first-line treatment in patients with RAS (KRAS/NRAS) wild-type metastatic colorectal cancer

TPS776

Background: Optimal combination of monoclonal antibody (anti-VEGF vs. anti-EGFR antibody) with standard chemotherapy as first-line treatment in patients (pts) with RAS (KRAS/NRAS) wild-type metastatic colorectal cancer (mCRC) remains controversial. FIRE-3 study demonstrated a significant improvement in overall survival (OS) with anti-EGFR over bevacizumab in pts with KRAS exon 2 wild type mCRC, while CALGB 80405 study did not. PARADIGM study is designed to compare panitumumab vs. bevacizumab combined with mFOLFOX6 in pts with RAS wild-type chemotherapy-naive mCRC. Methods: Eligible pts are aged 20-79 years with ECOG performance status (PS) 0-1 and histologically/cytologically confirmed RAS wild-type mCRC. 800 pts will be randomly assigned in a 1:1 ratio to mFOLFOX6 plus panitumumab or bevacizumab, and stratified according to institution, age (20-64 vs. 65-79 years), and liver metastases (present vs. absent). Each treatment regimen includes oxaliplatin 85 mg/m2, l-leucovorin 200 mg/m2, 5-fluorouracil (5-FU) iv 400 mg/m2 at day 1, 5-FU civ 2400 mg/m2 at day 1-3, and either panitumumab 6 mg/kg or bevacizumab 5 mg/kg at day 1 every two weeks. The primary endpoint is the OS; the study was designed to detect the OS hazard ratio of 0.76, with a one-sided type I error of 0.025 and 80% power. Secondary efficacy endpoints include progression-free survival, response rate, duration of response, and curative resection rate. One interim analysis is planned for the OS when approximately 70% of the targeted 570 events has been observed. Exploratory endpoint is to investigate possible biomarkers including oncogenic mutations using tumor tissue and circulating tumor DNA (Study ID: NCT02394834). As of August 2015, 21 pts have been randomized and recruitment is ongoing. Clinical trial information: NCT02394795.

Repeated piezoelectric lithotripsy for gallstones with and without ursodeoxycholic acid dissolution: a multicenter study

The use of bile acid dissolution therapy in extracorporeal shockwave lithotripsy of gallstones, remains controversial. Our study examined whether chemolitholysis after sufficient disintegration enhanced stone clearance within 6 months of the first lithotripsy. A total of 143 patients who developed one to three radiolucent stones measuring < or = 30 mm in diameter were randomly separated into two treatment groups: 47% were given lithotripsy alone, and 53% lithotripsy plus ursodeoxycholic acid (UDCA). Repeated piezoelectric lithotripsy was given, with no limit on the total number of treatment sessions, to pulverize or disintegrate stones into fragments < 3 mm. Stones were disintegrated in 97% of all patients, and the fragments were < or = 2 mm in 50% of these patients. According to an intention-to-treat analysis, 52% in the lithotripsy alone group and 58% in the UDCA group were free of stones 6 months after the first lithotripsy (P = 0.61). Of the patients with fragments < or = 2 mm, 71% in the former and 86% in the latter group were free of stones 6 months after the first lithotripsy, with no significant difference between the groups. Biliary pain occurred in 25% of all patients, including 3 with acute cholecystitis. We concluded that the sufficient disintegration of gallstones achieved with repeated lithotripsy enhanced the early clearance of fragments, regardless of whether chemolitholysis was employed.

Novel potassium channel openers: synthesis and pharmacological evaluation of new N-(substituted-3-pyridyl)-N'-alkylthioureas and related compounds

This report describes the synthesis and pharmacological evaluation of a series of novel potassium channel openers related to the pinacidil-type compounds. Thioureas, cyanoguanidines, and pyridine N-oxides were systematically evaluated for their effects on both the inhibition of spontaneous mechanical activity in rat portal vein (in vitro) and their antihypertensive activity (in vivo), and the structure-activity relationship for this series of compounds was discussed. Good correlation between in vitro and iv antihypertensive activity was observed for these compounds. Among them, cyanoguanidines bearing a conformationally rigid unit such as a norbornyl group generally possessed potent activity in both in vitro and in vivo studies. Especially, N-(6-amino-3-pyridyl)-N'-cyano-N"-(1-methyl-2-norbornyl)guanidine (23d) was identified as a more potent potassium channel opener in vitro (EC100 = 3 x 10(-8) M) than pinacidil (EC100 = 10(-7) M).

The effect of bilirubin on biliary lipid secretion: analysis by horseradish peroxidase associated intrahepatic vesicular transport system

The mechanism of biliary lipid secretion is still controversial and there is no definite information regarding how bilirubin inhibits biliary phospholipid and cholesterol secretions without affecting bile salt secretion. In this study, the effects of bilirubin on intrahepatic vesicular transport and biliary lipid secretion were examined using bile-fistula rats. Horseradish peroxidase (HRP) was used as a tracer of intrahepatic vesicular transport. Bilirubin (5 mg/100 g BW) and/or HRP (5 mg/100 gBW) were injected through the mesenteric vein. Bile flow, biliary bile acid, biliary phospholipid and cholesterol outputs were examined in saline, HRP and HRP + bilirubin groups, respectively. Bile flow and biliary bile acid output were not affected by bilirubin administration. Biliary phospholipid and cholesterol as well as biliary HRP outputs were inhibited just after bilirubin administration, 42.8 +/- 6.1 SD% 47.7 +/- 5.1 SD%, and 33.4 +/- 3.8 SD%, respectively. These results suggested the participation of intrahepatic vesicular transport system in the inhibition of biliary lipid secretion by bilirubin and in its secretory mechanism.