Whole-genome sequencing revealed novel prognostic biomarkers and promising targets for therapy of ovarian clear cell carcinoma

Clinical implications of next-generation sequencing-based panel tests for malignant ovarian tumors

Precision medicine based on cancer genomics is being applied in clinical practice. However, patients do not always derive benefits from genomic testing. Here, we performed targeted amplicon exome sequencing‐based panel tests, including 160 cancer‐related genes (PleSSision‐160), on 88 malignant ovarian tumors (high‐grade serous carcinoma, 27; endometrioid carcinoma, 15; clear cell carcinoma, 30; mucinous carcinoma, 6; undifferentiated carcinoma, 4; and others, 6 (immature teratoma, 1; carcinosarcoma, 3; squamous cell carcinoma, 1; and mixed, 1)), to assess treatment strategies and useful biomarkers for malignant ovarian tumors. Overall, actionable gene variants were found in 90.9%, and druggable gene variants were found in 40.9% of the cases. Actionable BRCA1 and BRCA2 variants were found in 4.5% of each of the cases. ERBB2 amplification was found in 33.3% of mucinous carcinoma cases. Druggable hypermutation/ultramutation (tumor mutation burden ≥ 10 SNVs/Mbp) was found in 7.4% of high‐grade serous carcinoma, 46.7% of endometrioid carcinoma, 10% of clear cell carcinoma, 0% of mucinous carcinoma, 25% of undifferentiated carcinoma, and 33.3% of the other cancer cases. Copy number alterations were significantly higher in high‐grade serous carcinoma (P < .005) than in other histologic subtypes; some clear cell carcinoma showed high copy number alterations that were correlated with advanced stage (P < .05) and worse survival (P < .01). A high count of copy number alteration was associated with worse survival in all malignant ovarian tumors (P < .05). Our study shows that targeted agents can be detected in approximately 40% of malignant ovarian tumors via multigene panel testing, and copy number alteration count can be a useful marker to help assess risks in malignant ovarian tumor patients.

The Landscape and Therapeutic Implications of Molecular Profiles in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) affects 43,000 women worldwide every year and has a five-year survival rate of 30%. Mainstay treatment is extensive surgery and chemotherapy. Outcomes could be improved by molecular profiling. We conducted a review of the literature to identify relevant publications on molecular and genetic alterations in EOC. Approximately 15% of all EOCs are due to BRCA1 or BRCA2 mutations. Four histologic subtypes characterized by different mutations have been described: serous, endometrioid, mucinous, and clear-cell. Between 20–30% of high-grade serous EOCs have a BRCA mutation. Tumors with BRCA mutations are unable to repair double-strand DNA breaks, making them more sensitive to platinum-based chemotherapy and to PolyAdenosine Diphosphate-Ribose Polymerase (PARP) inhibitors. Olaparib is a PARP inhibitor with proven efficacy in BRCA-mutated ovarian cancer, but its effectiveness remains to be demonstrated in tumors with a BRCAness (breast cancer) profile (i.e., also including sporadic tumors in patients with deficient DNA repair genes). A universally accepted molecular definition of BRCAness is required to identify optimal theranostic strategies involving PARP inhibitors. Gene expression analyses have led to the identification of four subgroups of high-grade serous EOC: mesenchymal, proliferative, differentiated, and immunoreactive. These subtypes are not mutually exclusive but are correlated with prognosis. They are not yet used in routine clinical practice. A greater understanding of EOC subtypes could improve patient management.

Endometriosis-Associated Ovarian Cancer: The Origin and Targeted Therapy

Endometrial cysts (ECs) are thought to be the origin of endometriosis-associated ovarian cancer (EAOC). A hypothesis that the oxidative stress of iron in cysts causes “malignant transformation of ECs” has been proposed, but this has not been verified. Several population-based studies showed that endometriosis was a risk factor but did not reflect the “malignant transformation of ECs”. A review showed that most patients were diagnosed with EAOC early in monitoring following detection of ECs, and that these cases might have been cancer from the start. Epidemiologically, EAOC was reduced by hysterectomy rather than by cystectomy of ECs. Gene mutation analyses identified oncogenic mutations in endometriosis and normal endometrium and revealed that the same mutations were present at different endometriotic lesions. It was also shown that most of the gene mutations found in endometriosis occurred in normal endometrium. Taking together, EAOC might be caused by eutopic endometrial glandular epithelial cells with oncogenic mutations that have undergone menstrual blood reflux and engrafted in the ovary, rather than by low-risk ECs acquiring oncogenic mutations and becoming malignant. This review discusses the mechanisms of EAOC development and targeted therapy based on genetic variation in EAOC with a focus on eutopic endometrium.

Prediction of breast cancer proteins involved in immunotherapy, metastasis, and RNA-binding using molecular descriptors and artificial neural networks

Breast cancer (BC) is a heterogeneous disease where genomic alterations, protein expression deregulation, signaling pathway alterations, hormone disruption, ethnicity and environmental determinants are involved. Due to the complexity of BC, the prediction of proteins involved in this disease is a trending topic in drug design. This work is proposing accurate prediction classifier for BC proteins using six sets of protein sequence descriptors and 13 machine-learning methods. After using a univariate feature selection for the mix of five descriptor families, the best classifier was obtained using multilayer perceptron method (artificial neural network) and 300 features. The performance of the model is demonstrated by the area under the receiver operating characteristics (AUROC) of 0.980 ± 0.0037, and accuracy of 0.936 ± 0.0056 (3-fold cross-validation). Regarding the prediction of 4,504 cancer-associated proteins using this model, the best ranked cancer immunotherapy proteins related to BC were RPS27, SUPT4H1, CLPSL2, POLR2K, RPL38, AKT3, CDK3, RPS20, RASL11A and UBTD1; the best ranked metastasis driver proteins related to BC were S100A9, DDA1, TXN, PRNP, RPS27, S100A14, S100A7, MAPK1, AGR3 and NDUFA13; and the best ranked RNA-binding proteins related to BC were S100A9, TXN, RPS27L, RPS27, RPS27A, RPL38, MRPL54, PPAN, RPS20 and CSRP1. This powerful model predicts several BC-related proteins that should be deeply studied to find new biomarkers and better therapeutic targets. Scripts can be downloaded at https://github.com/muntisa/neural-networks-for-breast-cancer-proteins.

Genomic and Molecular Abnormalities in Gynecologic Clear Cell Carcinoma

Gynecologic clear cell carcinoma is a rare histology, accounting for ~5% of all ovarian and endometrial cancers in the United States. Compared to other types of gynecologic cancer, they are generally less responsive to standard therapy and have an overall worse prognosis. In addition, mounting evidence suggests that the landscape of genetic and molecular abnormalities observed in these tumors is distinct from other cancers that arise from the same sites of origin. On a molecular level, these tumors characteristically display upregulation of the PI3K-AKT-mTOR and RAS-RAF-MAPK signaling axes, frequent loss of ARID1a, and overexpression of MDM2. Evidence also suggests that these tumors are more likely to express programmed death ligand 1 or demonstrate microsatellite instability than other gynecologic cancers. Despite these important differences, there has been relatively little investigation into histology-specific treatment of clear cell gynecologic cancers, representing an opportunity for new drug development. In this article, we review the unique genetic and molecular features of gynecologic clear cell cancers with an emphasis on potential therapeutic targets. The results of completed studies of treatment for clear cell carcinoma are also presented. We conclude with a discussion of ongoing clinical trials and potential avenues for future study.

Translational genomics of ovarian clear cell carcinoma

Ovarian clear cell carcinomas (OCCC) are rare aggressive, chemo-resistant tumours comprising approximately 13% of all epithelial ovarian cancers, which have distinct clinical and molecular features, when compared to other gynaecological malignancies. At present, there are no specific licensed targeted therapies for OCCC, although a number of candidate targets have been identified. This review focuses on recent knowledge underpinning our understanding of the pathogenesis of OCCC including direct and synthetic-lethal therapeutic strategies in particular focussing on ARID1A deficiency. We also discuss current targeted clinical trials and immunotherapeutic approaches.

Precision medicine for ovarian clear cell carcinoma based on gene alterations

Ovarian clear cell carcinoma (OCCC) is a histological subtype of epithelial ovarian carcinoma prevalent in Asians. No clear therapeutic selection based on molecular profile has been implemented for this disease. Oncogenic PIK3CA mutation, which activates the PIK3CA/AKT/mTOR signaling pathway, is a promising druggable alteration in OCCC. Recent studies by our group and others have identified the ARID1A mutation as another alteration linked to therapeutic selection based on synthetic lethality: deleterious ARID1A mutations, resulting in ARID1A deficiency, make OCCC cells sensitive to drugs targeting poly (ADP-ribose) polymerase and EZH2, as well as to glutathione inhibitors. In addition, we recently obtained evidence that ARID1A-deficient OCCC could benefit from gemcitabine treatment. Precision medicine based on gene alteration profiling might improve the prognosis of OCCC patients.

Pathology of Endometrioid and Clear Cell Carcinoma of the Ovary

This review is an appraisal of the current state of knowledge of 2 enigmatic histotypes of ovarian carcinoma: endometrioid and clear cell carcinoma. Both show an association endometriosis and the hereditary nonpolyposis colorectal cancer (Lynch) syndrome, and both typically present at an early stage. Pathologic and immunohistochemical features that distinguish these tumors from high-grade serous carcinomas, each other, and other potential mimics are discussed, as are staging, grading, and molecular pathogenesis.

Germline and somatic mutations of homologous recombination-associated genes in Japanese ovarian cancer patients

We explored the frequency of germline and somatic mutations in homologous recombination (HR)-associated genes in major histological types of ovarian cancer. We performed targeted sequencing to assess germline and somatic mutations of 16 HR-associated genes and 4 mismatch repair (MMR) genes among 207 ovarian cancer patients (50 high-grade serous carcinomas (HGSC), 99 clear cell carcinomas (CCC), 39 endometrioid carcinomas (EC), 13 mucinous carcinomas (MC), and 6 low-grade serous carcinomas (LGSC)). Germline or somatic mutations of HR-associated genes were detected in 44% of HGSC, 28% of CCC, 23% of EC, 16% of MC, and 17% of LGSC patients. The profile of HR-associated gene mutations was remarkably different among each histological type. Germline BRCA1/2 mutations were frequently detected in HGSC and were rarely observed in CCC, EC, and MC patients. ATM somatic mutation was more frequently detected in CCC (9%) and EC patients (18%) than in HGSC patients (4%). There was a positive correlation between MMR gene mutations and HR-associated gene mutations (p = 0.0072). Our findings might be useful in selection of ovarian cancer patients that should be treated with PARP inhibitors.

BRM: the core ATPase subunit of SWI/SNF chromatin-remodelling complex-a tumour suppressor or tumour-promoting factor?

BRM (BRAHMA) is a core, SWI2/SNF2-type ATPase subunit of SWI/SNF chromatin-remodelling complex (CRC) involved in various important regulatory processes including development. Mutations in SMARCA2, a BRM-encoding gene as well as overexpression or epigenetic silencing were found in various human diseases including cancer. Missense mutations in SMARCA2 gene were recently connected with occurrence of Nicolaides-Baraitser genetics syndrome. By contrast, SMARCA2 duplication rather than mutations is characteristic for Coffin-Siris syndrome. It is believed that BRM usually acts as a tumour suppressor or a tumour susceptibility gene. However, other studies provided evidence that BRM function may differ depending on the cancer type and the disease stage, where BRM may play a role in the disease progression. The existence of alternative splicing forms of SMARCA2 gene, leading to appearance of truncated functional, loss of function or gain-of-function forms of BRM protein suggest a far more complicated mode of BRM-containing SWI/SNF CRCs actions. Therefore, the summary of recent knowledge regarding BRM alteration in various types of cancer and highlighting of differences and commonalities between BRM and BRG1, another SWI2/SNF2 type ATPase, will lead to better understanding of SWI/SNF CRCs function in cancer development/progression. BRM has been recently proposed as an attractive target for various anticancer therapies including the use of small molecule inhibitors, synthetic lethality induction or proteolysis-targeting chimera (PROTAC). However, such attempts have some limitations and may lead to severe side effects given the homology of BRM ATPase domain to other ATPases, as well as due to the tissue-specific appearance of BRM- and BRG1-containing SWI/SNF CRC classes. Thus, a better insight into BRM-containing SWI/SNF CRCs function in human tissues and cancers is clearly required to provide a solid basis for establishment of new safe anticancer therapies.

Resibufogenin inhibits ovarian clear cell carcinoma (OCCC) growth in vivo, and migration of OCCC cells in vitro, by down-regulating the PI3K/AKT and actin cytoskeleton signaling pathways

Patients diagnosed with ovarian clear cell carcinoma (OCCC), a rare histologic subtype of ovarian cancer, often experience poor prognosis owing to the chemoresistance of their disease. Thus, there is an urgent need to identify new therapeutic options for these patients. A drug screen of 172 traditional Chinese herbs identified resibufogenin as a compound that inhibited the growth of cultured OCCC cells. Resibufogenin, a bioactive compound originally isolated from toad venom, is used in traditional Chinese medicine to treat several malignancies. The current study examined the impact of resibufogenin treatment on proliferation, migration, and invasion of ES-2 and TOV-21G OCCC cells in vitro. Flow cytometric analyses were employed to determine if resibufogenin affects apoptosis in OCCC cells. Additionally, the ability of resibufogenin to inhibit tumor growth in vivo was evaluated in murine xenograft models. RNA sequencing, quantitative polymerase chain reactions (qPCR), immunohistochemical assays, and western blotting were used to identify and verify cellular pathways potentially targeted by resibufogenin. Resibufogenin inhibited proliferation, migration, and invasion of OCCC cells, and induced apoptosis in them. Resibufogenin also suppressed the growth of xenograft tumors, which consequently showed lower Ki-67 and higher terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) expression. We observed down-regulation of (a) PI3K and AKT in the PI3K/AKT signaling pathway, and (b) MDM2 and myosin in the actin cytoskeleton pathway upon resibufogenin treatment. Thus, resibufogenin inhibits growth and migration of OCCC cells in vitro and suppresses OCCC growth in vivo through the PI3K/AKT and actin cytoskeleton signaling pathways.

Low-dose triple drug combination targeting the PI3K/AKT/mTOR pathway and the MAPK pathway is an effective approach in ovarian clear cell carcinoma

Advanced stage ovarian clear cell carcinoma (OCCC) is poorly responsive to platinum-based chemotherapy and has an unfavorable prognosis. Previous studies revealed heterogeneous mutations in PI3K/AKT/mTOR and MAPK pathway nodules converging in mTORC1/2 activation. Here, we aimed to identify an effective low-dose combination of PI3K/AKT/mTOR pathway and MAPK pathway inhibitors simultaneously targeting key kinases in OCCC to preclude single-inhibitor initiated pathway rewiring and limit toxicity. Small molecule inhibitors of mTORC1/2, PI3K and MEK1/2 were combined at monotherapy IC₂₀ doses in a panel of genetically diverse OCCC cell lines (n = 7) to determine an optimal low-dose combination. The IC₂₀ dose triple combination reduced kinase activity in PI3K/AKT/mTOR and MAPK pathways, prevented single-inhibitor induced feedback mechanisms and inhibited short and long-term proliferation in all seven cell lines. Finally, this low-dose triple drug combination treatment significantly reduced tumor growth in two genetically characterized OCCC patient-derived xenograft (PDX) models without resulting in weight loss in these mice. The effectiveness and tolerability of this combined therapy in PDX models warrants clinical exploration of this treatment strategy for OCCC and might be applicable to other cancer types with a similar genetic background.

Epithelial ovarian cancer: Evolution of management in the era of precision medicine

Ovarian cancer is the second most common cause of gynecologic cancer death in women around the world. The outcomes are complicated, because the disease is often diagnosed late and composed of several subtypes with distinct biological and molecular properties (even within the same histological subtype), and there is inconsistency in availability of and access to treatment. Upfront treatment largely relies on debulking surgery to no residual disease and platinum-based chemotherapy, with the addition of antiangiogenic agents in patients who have suboptimally debulked and stage IV disease. Major improvement in maintenance therapy has been seen by incorporating inhibitors against poly (ADP-ribose) polymerase (PARP) molecules involved in the DNA damage-repair process, which have been approved in a recurrent setting and recently in a first-line setting among women with BRCA1/BRCA2 mutations. In recognizing the challenges facing the treatment of ovarian cancer, current investigations are enlaced with deep molecular and cellular profiling. To improve survival in this aggressive disease, access to appropriate evidence-based care is requisite. In concert, realizing individualized precision medicine will require prioritizing clinical trials of innovative treatments and refining predictive biomarkers that will enable selection of patients who would benefit from chemotherapy, targeted agents, or immunotherapy. Together, a coordinated and structured approach will accelerate significant clinical and academic advancements in ovarian cancer and meaningfully change the paradigm of care.

Survival Following Chemotherapy in Ovarian Clear Cell Carcinoma Is Not Associated with Pathological Misclassification of Tumor Histotype

PURPOSE

Although ovarian clear cell carcinomas (OCCC) are commonly resistant to platinum-based chemotherapy, good clinical outcomes are observed in a subset of patients. The explanation for this is unknown but may be due to misclassification of high-grade serous ovarian cancer (HGSOC) as OCCC or mixed histology.

EXPERIMENTAL DESIGN

To discover potential biomarkers of survival benefit following platinum-based chemotherapy, we ascertained a cohort of 68 Japanese and Australian patients in whom progression-free survival (PFS) and overall survival (OS) could be assessed. We performed IHC reclassification of tumors, and targeted sequencing and immunohistochemistry of known driver genes. Exome sequencing was performed in 10 patients who had either unusually long survival (N = 5) or had a very short time to progression (N = 5).

RESULTS

The majority of mixed OCCC (N = 6, 85.7%) and a small proportion of pure OCCC (N = 3, 4.9%) were reclassified as likely HGSOC. However, the PFS and OS of patients with misclassified samples were similar to that of patients with pathologically validated OCCC. Absent HNF1B expression was significantly correlated with longer PFS and OS (P = 0.0194 and 0.0395, respectively). Mutations in ARID1A, PIK3CA, PPP2R1A, and TP53 were frequent, but did not explain length of PFS and OS. An exploratory exome analysis of patients with favorable and unfavorable outcomes did not identify novel outcome-associated driver mutations.

CONCLUSIONS

Survival benefit following chemotherapy in OCCC was not associated with pathological misclassification of tumor histotype. HNF1B loss may help identify the subset of patients with OCCC with a more favorable outcome.

Research progress on the PI3K/AKT signaling pathway in gynecological cancer (Review)

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway is involved in the regulation of multiple cellular physiological processes by activating downstream corresponding effector molecules, which serve an important role in the cell cycle, growth and proliferation. This is a common phenomenon; overactivation of the pathway is present in human malignancies and has been implicated in cancer progression, hence one of the important approaches to the treatment of tumors is rational drug design using molecular targets in the PI3K/AKT signaling pathway. In brief, the present review analyzed the effects of the PI3K/AKT signaling pathway on certain gynecological cancer types.

Genomics to immunotherapy of ovarian clear cell carcinoma: Unique opportunities for management

Ovarian clear cell carcinoma (OCCC) is distinctive from other histological types of epithelial ovarian cancer, with genetic/epigenetic alterations, a specific immune-related molecular profile, and epidemiologic associations with ethnicity and endometriosis. These findings allow for the exploration of unique and specific treatments for OCCC. Two major mutated genes in OCCC are PIK3CA and ARID1A, which are frequently coexistent with each other. Other genes' alterations also contribute to activation of the PI3K (e.g. PIK3R1 and PTEN) and dysregulation of the chromatin remodeling complex (e.g. ARID1B, and SMARKA4). Although the number of focal copy number variations is small in OCCC, amplification is recurrently detected at chromosome 20q13.2 (including ZNF217), 8q, and 17q. Both expression and methylation profiling highlight the significance of adjustments to oxidative stress and inflammation. In particular, up-regulation of HNF-1β resulting from hypomethylation contributes to the switch from anaerobic to aerobic glucose metabolism. Additionally, up-regulation of HNF-1β activates STAT3 and NF-κB signaling, and leads to immune suppression via production of IL-6 and IL-8. Immune suppression may also be induced by the increased expression of PD-1, Tim-3 and LAG3. Mismatch repair deficient (microsatellite instable) tumors as found in Lynch syndrome also induce immune suppression in some OCCC. In a recent phase II clinical trial in heavily-treated platinum-resistant ovarian cancer, two out of twenty cases with a complete response to the anti-PD-1 antibody, nivolumab, were OCCC subtypes. Thus, the immune-suppressive state resulting from both genetic alterations and the unique tumor microenvironment may be associated with sensitivity to immune checkpoint inhibitors in OCCC. In this review, we highlight recent update and progress in OCCC from both the genomic and immunologic points of view, addressing the future candidate therapeutic options.

ARID1A mutant ovarian clear cell carcinoma: A clear target for synthetic lethal strategies

SWI/SNF chromatin remodeling complexes play an important role in the epigenetic regulation of chromatin structure and gene transcription. Mutual exclusive subunits in the SWI/SNF complex include the DNA targeting members ARID1A and ARID1B as well as the ATPases SMARCA2 and SMARCA4. SWI/SNF complexes are mutated across many cancer types. The highest mutation incidence is found in ARID1A, primarily consisting of deleterious mutations. Current advances have reported synthetic lethal interactions with the loss of ARID1A in several cancer types. In this review, we discuss targets that are only important for tumor growth in an ARID1A mutant context. We focus on synthetic lethal strategies with ARID1A loss in ovarian clear cell carcinoma, a cancer with the highest ARID1A mutation incidence (46-57%). ARID1A directed lethal strategies that can be exploited clinically include targeting of the DNA repair proteins PARP and ATR, and the epigenetic factors EZH2, HDAC2, HDAC6 and BRD2.

Next-generation sequencing unravels extensive genetic alteration in recurrent ovarian cancer and unique genetic changes in drug-resistant recurrent ovarian cancer

BACKGROUND

By using a high-throughput sequencing technique, we sought to delineate genetic alterations in recurrent ovarian cancer patients and further compare genetic changes in drug-resistant and -sensitive recurrent ovarian cancer patients. We also sought to study the specificity, sensitivity, and consistency of DNA biomarkers in liquid biopsy specimens and ovarian cancer tissue DNA.

METHODS

Tumor tissue specimens and blood samples were obtained from pathologically proven recurrent ovarian cancer patients. Genomic DNA was extracted from tumor tissues, blood cells, ascites, and urine samples. The DNA Library was constructed and sequencing was performed using the Illumina HiSeq 4000 high-throughput sequencing platform. Bioinformatic analysis was done using the Torrent Suite software.

RESULTS

Ten patients with pathologically proven drug-resistant recurrent ovarian cancer and 11 patients with sensitive recurrent ovarian cancer were included. The 5-year OS for drug-resistant recurrent ovarian cancer patients (44 ± 11.07 months, 95% CI: 231.24-53.66 months) was significantly lower than that of drug-sensitive recurrent ovarian cancer patients (58 ± 3.97 months; 95% CI: 50.05-65.59 months; p = 0.024) TP53 was the most frequently mutated gene in both drug-resistant (9/10, 90%) and drug-sensitive recurrent ovarian cancers (10/11, 91%). MYC and RB1 had the highest frequency of copy number variations (6/21, 29%) in recurrent ovarian cancers, followed by PIK3CA (3/21, 14%). BRCA2 N372H polymorphism was found in 40% (4/10) of drug-resistant recurrent ovarian cancer patients. The specificity, sensitivity, and consistency of TP53 and BRCA1 in circulating tumor-free DNA and tumor tissue DNA were 100%, 73.7%, 76.2% and 100%, 75%, 95.24%, respectively.

CONCLUSION

We uncovered extensive genetic alterations in recurrent ovarian cancer and drug-resistant recurrent ovarian cancer exhibited unique genetic changes compared with recurrent ovarian cancer and drug-sensitive recurrent ovarian cancer. We further showed that high-throughput sequencing using liquid biopsy specimens could provide an effective, specific, and sensitive approach for detecting genetic alterations in ovarian cancer.

Role of endometriosis as a prognostic factor for post-progression survival in ovarian clear cell carcinoma

The clinical significance of coexistence of endometriosis (EM) in ovarian clear cell carcinoma (CCC) has not yet been determined. The aim of the present study was to analyze the correlation of endometriosis with clinicopathological factors in CCC. The cases with CCC that received primary debulking surgery at the present hospital between 1990 and 2013 were identified. Retrospective analysis was conducted to evaluate the association between complications with EM and clinicopathological features in CCC. Of the 105 cases enrolled in the study, 45 cases were complicated with EM, and 60 cases did not have EM (non-EM). The patients with EM were diagnosed at a younger age (P=0.03), and at earlier stages (P<0.01) compared with non-EM cases. Although there was no significant difference of progression-free survival (P=0.36), complications with EM were identified as an independent prognostic factor for overall survival (OS; P<0.01) by multivariate analysis. A total of 48 patients (45.7%) developed recurrence: 18 patients in EM-group and 30 patients in non-EM group. There were no significant differences of clinicopathological factors in the treatment at recurrence between both groups. Recurrent cases in EM had significantly worse post-progression survival (PPS) compared with recurrent non-EM group (P<0.01). Multivariate analysis for PPS demonstrated that complications with EM (P<0.01) were identified as a worse prognostic factor. In CCC, the complication with EM was identified as a significant worse prognostic factor for PPS in recurrent cases. Additionally, EM was significantly associated with OS in all cases with CCC. Novel treatment strategies are therefore necessary for recurrent CCC, particularly for cases exhibiting EM.