FGFR2-IIIb Expression by Immunohistochemistry Has High Specificity in Cholangiocarcinoma with FGFR2 Genomic Alterations

FGFR2 fusions assessed by NGS, FISH, and immunohistochemistry in intrahepatic cholangiocarcinoma

BACKGROUND

FGFR2 fusion has become a promising therapeutic target in iCCAs; however, the procedure for screening FGFR2 fusion has not been conventionally developed.

METHODS

FGFR2 fusion was identified using DNA + RNA-based NGS and FISH, and the concordance between DNA + RNA-based NGS, FISH, and IHC was compared.

RESULTS

FGFR2 fusions were detected in 9 out of 76 iCCAs (11.8%). The consistency of FISH and DNA + RNA-based NGS for FGFR2 fusions was high (κ value = 0.867, P = 0.001), while the consistency of IHC and DNA + RNA-based NGS was lower (κ value = 0.464, P = 0.072). All nine FGFR2 fusion-positive iCCAs were MSS with a median TMB of 2.1 mut/Mb, and only one had a CPS (PD-L1) above 5. Two FGFR2 fusion-positive iCCA patients were treated with and benefited from FGFR inhibitor therapy.

CONCLUSIONS

FGFR2 fusion should be assessed for advanced iCCA patients. We recommend DNA + RNA-based NGS as the preferred option to supply all possible therapeutic targets. FISH should be preferred if the tumor sample is insufficient for NGS or if the patient is inclined to receive FGFR inhibitors promptly. Although IHC is not the preferred method to identify FGFR2 fusion, it might be used as preliminary screening for FGFR2 alterations if the hospital cannot offer NGS or FISH, and the results need to be validated before FGFR2 inhibitors treatment.

Expression of fibroblast growth factor receptor 2 (FGFR2) in combined hepatocellular-cholangiocarcinoma and intrahepatic cholangiocarcinoma: clinicopathological study

Genetic alterations including fusions in fibroblast growth factor receptor 2 (FGFR2) are detected in 10-20% of intrahepatic cholangiocarcinoma (iCCA), and FGFR2 inhibitors are effective for the treatment of iCCA. We examined a prevalence of FGFR2 genetic alterations and their clinicopathological significance in combined hepatocellular-cholangiocarcinoma (cHCC-CCA). FGFR2 expression, which is a surrogate marker for FGFR2 genetic alterations, was immunohistochemically assessed in the liver sections from 75 patients with cHCC-CCA, 35 with small duct-type iCCA, 30 with large duct-type iCCA, and 35 with hepatocellular carcinoma (HCC). FGFR2 genetic alterations were detected by reverse transcription-PCR and direct sequence. An association of FGFR2 expression with clinicopathological features was investigated in cHCC-CCAs. FGFR2 expression was detected in significantly more patients with cHCC-CCA (21.3%) and small duct-type iCCA (25.7%), compared to those with large duct-type iCCA (3.3%) and HCC (0%) (p < 0.05). FGFR2-positive cHCC-CCAs were significantly smaller size (p < 0.05), with more predominant cholangiolocarcinoma component (p < 0.01) and less nestin expression (p < 0.05). Genetic alterations of ARID1A and BAP1 and multiple genes were significantly more frequent in FGFR2-positive cHCC-CCAs (p < 0.05). 5'/3' imbalance in FGFR2 genes indicating exon18-truncated FGFR2 was significantly more frequently detected in FGFR2-positive cHCC-CCAs and small duct iCCAs, compared to FGFR2-negative ones (p < 0.05). FGFR2::BICC fusion was detected in a case of cHCC-CCAs. FGFR2 genetic alterations may be prevalent in cHCC-CCAs as well as small duct-type iCCAs, which suggest cHCC-CCAs may also be a possible therapeutic target of FGFR2 inhibitors.

Clinical Utility of Ivosidenib in the Treatment of IDH1-Mutant Cholangiocarcinoma: Evidence To Date

Ivosidenib is an isocitrate dehydrogenase 1 (IDH1) inhibitor that is FDA approved for patients with IDH1 mutation and acute myeloid leukemia and previously treated locally advanced or metastatic cholangiocarcinoma. In the Phase III trial ClarIDHy ivosidenib improved progression-free survival, 2.7 months versus 1.4 months (p < 0.0001) and overall survival (OS), median OS was 10.8 months for ivosidenib and 9.7 months for the placebo arm (p = 0.06) for patients with previously treated and IDH1 mutated cholangiocarcinoma. In this review article, we will address the mechanism of action of ivosidenib and data from early trials and safety from the randomized trial in cholangiocarcinoma. As a conclusion, future perspectives of IDH1 inhibition in IDH1 mutated tumors and possible strategies of sequencing and combinations will be reviewed and discussed.

Novel precision therapies for cholangiocarcinoma: an overview of clinical trials

INTRODUCTION

The treatment landscape of biliary cancers is rapidly changing. Inhibitors against the actionable targets FGFR and IDH1 are now being included in the treatment guidelines of multiple countries for patients with advanced cholangiocarcinoma. However, there remains an unmet need in identifying the mechanisms of resistance and treatment strategies involving possible tumor sequencing.

AREAS COVERED

In this review article, we address clinical trials evaluating FGFR, IDH, BRAF and HER2 inhibitors in advanced cholangiocarcinoma. We also review the mechanisms of resistance described thus far and approaches to overcome them. Articles selected for this review were based on reported studies indexed in PubMed (2010-2022).

EXPERT OPINION

Precision medicine in biliary cancers has already been incorporated into the treatment landscape of the disease in many countries. Fusions of FGFR2 and mutations in IDH1 are the first drivers with targetable treatments approved in these cancers. HER2 and BRAF would be the next drivers with possible tumor-agnostic or cholangiocarcinoma-specific approvals. The advent of ctDNA could improve the accessibility of sequencing and recruitment in these clinical trials. However, limitations of detecting fusions should be considered and addressed in these platforms.

Patient Selection Approaches in FGFR Inhibitor Trials-Many Paths to the Same End?

Inhibitors of fibroblast growth factor receptor (FGFR) signaling have been investigated in various human cancer diseases. Recently, the first compounds received FDA approval in biomarker-selected patient populations. Different approaches and technologies have been applied in clinical trials, ranging from protein (immunohistochemistry) to mRNA expression (e.g., RNA in situ hybridization) and to detection of various DNA alterations (e.g., copy number variations, mutations, gene fusions). We review, here, the advantages and limitations of the different technologies and discuss the importance of tissue and disease context in identifying the best predictive biomarker for FGFR targeting therapies.