Chemosensitivity testing of ovarian cancer using the histoculture drug response assay: sensitivity to cisplatin and clinical response

Preclinical models of epithelial ovarian cancer: practical considerations and challenges for a meaningful application

Despite many improvements in ovarian cancer diagnosis and treatment, until now, conventional chemotherapy and new biological drugs have not been shown to cure the disease, and the overall prognosis remains poor. Over 90% of ovarian malignancies are categorized as epithelial ovarian cancers (EOC), a collection of different types of neoplasms with distinctive disease biology, response to chemotherapy, and outcome. Advances in our understanding of the histopathology and molecular features of EOC subtypes, as well as the cellular origins of these cancers, have given a boost to the development of clinically relevant experimental models. The overall goal of this review is to provide a comprehensive description of the available preclinical investigational approaches aimed at better characterizing disease development and progression and at identifying new therapeutic strategies. Systems discussed comprise monolayer (2D) and three-dimensional (3D) cultures of established and primary cancer cell lines, organoids and patient-derived explants, animal models, including carcinogen-induced, syngeneic, genetically engineered mouse, xenografts, patient-derived xenografts (PDX), humanized PDX, and the zebrafish and the laying hen models. Recent advances in tumour-on-a-chip platforms are also detailed. The critical analysis of strengths and weaknesses of each experimental model will aid in identifying opportunities to optimize their translational value.

Prospective Clinical Correlation of the Histoculture Drug Response Assay for Ovarian Cancer

The histoculture drug response assay (HDRA) has been correlated clinically to a number of cancer types (please see Chaps. 7 - 11 of the present volume). The present chapter reviews the clinical trials of the HDRA for ovarian cancer. A prospective clinical trial of the HDRA for advanced epithelial ovarian cancer (AEOC) was performed at Asan Medical Center, Seoul, Korea. The clinical trial compared the efficacy of first-line therapy paclitaxel and carboplatinum in the HDRA and the clinical response for the patients whose tumors were tested in the HDRA. A series of patients (104) were treated with adjuvant combination chemotherapy of paclitaxel and carboplatinum after primary cytoreductive surgery. Tumor fragments were cultured on Gelfoam^® and tested with paclitaxel and carboplatinum and evaluated with the MTT endpoint. Patients were categorized into two groups as either sensitive to both drugs (SS) or not sensitive to one or both drugs (R) based on HDRA results. The recurrence rate was much lower in the SS group compared to the R group, 29.2% vs. 69.8%, respectively. The SS group had a significantly longer progression-free survival compared to the R group, 34.0 months vs. 16.0 months, respectively. In another clinical trial, the HDRA was performed on 85 cases of ovarian cancer and 97% were evaluable. HDRA results were correlated to clinical response of 15 patients who received cisplatinum-based therapy that included doxorubicin and cyclophosphamide (CAP therapy). The true-positive rate was 88%, the true-negative rate was 86%, the sensitivity was 88%, the specificity was 86%, and the accurate prediction rate was 87% when HDRA results were compared to the response of the treated patients.

Clinical Usefulness of the Histoculture Drug Response Assay for Breast Cancer

The histoculture drug response assay (HDRA) was used to compare drug sensitivity of recurrent and primary breast cancer in vitro as well as in the clinic. The HDRA utilizes 3-dimensional culture of human tumors on Gelfoam^®. The evaluation rate was 98.8%. The HDRA mean inhibition rate of primary tumors vs. recurrent tumors was, respectively, 57.9% and 38.6% for doxorubicin (DOX); 59.9% and 42.8% for mitomycin C (MMC); 49.0% and 33.4% for 5-fluorouracil (5-FU); and 34.5% and 16.0% for cisplatinum (CDDP). The recurrent cases were pretreated clinically with CAF (cyclophosphamide [CTX], DOX, and 5-FU), CEF (CTX, epirubicin [EPN], and 5-FU), or CMF (CTX, methotrexate [MTX], and 5-FU). 64.7% of the recurrent cases were resistant to all four agents tested compared to 27% of the primary cases. Only 5.9% of the recurrent cases were sensitive to three or more agents as opposed to 18% of the primary cases. The correlation of the HDRA results to clinical outcome in another breast-cancer study was 80.0% with 15 cases evaluated consisting of five true positives, three false positives, seven true negatives, and no false negatives. HDRA was also performed on surgical specimens of primary tumor and axillary lymph node metastasis from each of 30 breast cancer patients. The lymph-node metastases were more resistant than the primary tumor for DOX, 5-FU, and MMC, but not for CDDP. The data suggest that both primary tumor and metastases from individual patients should be tested in the HDRA to enhance clinical efficacy of chemotherapy. There also was a lack of correlation with breast cancer subtype and drug response in the HDRA, further suggesting the importance of individualized treatment for breast cancer patients afforded by the HDRA.

Novel ex vivo ovarian cancer tissue explant assay for prediction of chemosensitivity and response to novel therapeutics

The majority of ovarian cancer patients present with advanced disease and despite aggressive treatment, prognosis remains poor. Response to first-line carboplatin-containing chemotherapy is usually good, however, recurrence rates and subsequent chemoresistance are very high and ultimately responsible for the fatal outcome of the disease. To improve treatment outcomes pre-clinical models that can predict individual patient response to 1st line chemotherapy and novel therapeutics are urgently required. In this study, we employed an ex vivo ovarian cancer tissue explant assay to assess response to carboplatin and an inhibitor of the extracellular matrix molecule, hyaluronan (4-methylubelliferone, 4-MU), shown to inhibit cancer metastasis. Cryopreserved ovarian cancer tissues were cultured on gelatine sponges for 48-120 h with increasing concentrations of carboplatin (0-400 μM) or 4-MU (1 mM) alone or the combination of both drugs. Effects on apoptosis and proliferation were assessed by immunohistochemistry using antibodies to cleaved caspase 3 or Ki67, respectively. The ex vivo tissue explant assay maintained viable tumor cells in an intact tumor microenvironment similar to the in vivo situation over the 120 h culture period. Carboplatin treatment promoted apoptosis in chemosensitive (P = 0.0047) but not chemoresistant cancer tissues. The combination of 4-MU (1 mM) and carboplatin (100 μM) significantly increased apoptosis (P = 0.0111) and reduced proliferation (P = 0.0064) in chemoresistant tissues. Overall, our results show that the ex vivo explant assay is a robust and cost effective model to assess chemosensitivity and the effect of novel therapeutics in ovarian cancer.

Evolution of Chemosensitivity and Resistance Assays as Predictors of Clinical Outcomes in Epithelial Ovarian Cancer Patients

Epithelial ovarian cancer (EOC) is responsible for more cancer-related deaths than any other malignancy of the female reproductive system. The standard of care for advanced EOC involves a combination of cytoreductive surgery and platinum-based chemotherapy. Although a majority of patients respond to a platinum-containing regimen, many fail to respond to first-line treatment (platinum-refractory disease) or experience disease progression within 6 months of completing treatment (platinum-resistant disease). Even in patients who initially respond to platinum-based therapy, secondary development of platinum resistance is common. Many chemotherapeutic regimens with comparable efficacy and toxicities are available, leaving the determination of optimal therapy to the physician's discretion. There have been many efforts over the years to develop accurate predictors of outcomes in patients treated with chemotherapy to help inform treatment decisions. Predictive treatment markers are particularly relevant in a disease such as EOC, where a large number of similarly efficacious chemotherapy regimens are available. Chemosensitivity and resistance assays (CSRAs) are attractive approaches to interrogate the efficacy and complex biology of EOC. Some early predictive cellular tests, such as the early clonogenic assays, were limited by technical and logistical issues. Over time, changes in these assays have improved their prognostic and predictive value, but there is still a lack of widespread adoption due to methodological difficulties or limited clinical validation. Herein, we provide an overview of the evolution of CSRAs used to predict outcomes in patients treated with chemotherapy that have been evaluated for use in EOC, with a focus on the latest generation chemoresponse assay.

Prediction of Cancer Drug Resistance and Implications for Personalized Medicine

Drug resistance still impedes successful cancer chemotherapy. A major goal of early concepts in individualized therapy was to develop in vitro tests to predict tumors’ drug responsiveness. We have developed an in vitro short-term test based on nucleic acid precursor incorporation to determine clinical drug resistance. This test detects inherent and acquired resistance in vitro and transplantable syngeneic and xenografted tumors in vivo. In several clinical trials, clinical resistance was predictable with more than 90% accuracy, while drug sensitivity was detected with less accuracy (~60%). Remarkably, clinical cross-resistance to numerous drugs (multidrug resistance, broad spectrum resistance) was detectable by a single compound, doxorubicin, due to its multifactorial modes of action. The results of this predictive test were in good agreement with predictive assays of other authors. As no predictive test has been established as yet for clinical diagnostics, the identification of sensitive drugs may not reach sufficiently high reliability for clinical routine. A meta-analysis of the literature published during the past four decades considering test results of more than 15,000 tumor patients unambiguously demonstrated that, in the majority of studies, resistance was correctly predicted with an accuracy between 80 and 100%, while drug sensitivity could only be predicted with an accuracy of 50–80%. This synopsis of the published literature impressively illustrates that prediction of drug resistance could be validated. The determination of drug resistance was reliable independent of tumor type, test assay, and drug used in these in vitro tests. By contrast, chemosensitivity could not be predicted with high reliability. Therefore, we propose a rethinking of the “chemosensitivity” concept. Instead, predictive in vitro tests may reliably identify drug-resistant tumors. The clinical consequence imply to subject resistant tumors not to chemotherapy, but to other new treatment options, such as antibody therapy, adoptive immune therapy, hyperthermia, gene therapy, etc. The high accuracy to predict resistant tumors may be exploited to develop new strategies for individualized cancer therapy. This new concept bears the potential of a revival of predictive tests for personalized medicine.

Factors affecting platinum sensitivity in cervical cancer

The present study aimed to investigate the association between nedaplatin (NDP) sensitivity and the expression of biological factors in cervical cancer. A total of 45 cervical cancer specimens, including 18 pretreatment biopsies and 27 surgical specimens, were used in histoculture drug response assays to determine the chemosensitivity of cervical cancer specimens to NDP. Each specimen was assessed for immunohistochemical expression of Ki-67, p53, B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), cleaved caspase-3, cyclooxygenase-2 (COX-2), and excision repair cross-complementation group 1 (ERCC1). The results revealed that low or negative expression of p53, Bcl-2 and COX-2, and high or positive expression of cleaved caspase-3 were significantly correlated with high sensitivity to NDP. However, there were no significant differences in Ki-67, Bax or ERCC1 expression between the low and high sensitivity groups. These findings indicate that sensitivity to platinum may be easily predicted by immunostaining for the detection of these specific factors in pretreatment biopsies or surgical specimens. The expression profiles of these targets may therefore provide additional information for planning individualized chemotherapy in the treatment of cervical cancer.

Feasibility of Primary Tumor Culture Models and Preclinical Prediction Assays for Head and Neck Cancer: A Narrative Review

Primary human tumor culture models allow for individualized drug sensitivity testing and are therefore a promising technique to achieve personalized treatment for cancer patients. This would especially be of interest for patients with advanced stage head and neck cancer. They are extensively treated with surgery, usually in combination with high-dose cisplatin chemoradiation. However, adding cisplatin to radiotherapy is associated with an increase in severe acute toxicity, while conferring only a minor overall survival benefit. Hence, there is a strong need for a preclinical model to identify patients that will respond to the intended treatment regimen and to test novel drugs. One of such models is the technique of culturing primary human tumor tissue. This review discusses the feasibility and success rate of existing primary head and neck tumor culturing techniques and their corresponding chemo- and radiosensitivity assays. A comprehensive literature search was performed and success factors for culturing in vitro are debated, together with the actual value of these models as preclinical prediction assay for individual patients. With this review, we aim to fill a gap in the understanding of primary culture models from head and neck tumors, with potential importance for other tumor types as well.

Prediction of individual response to anticancer therapy: historical and future perspectives

Since the introduction of chemotherapy for cancer treatment in the early 20th century considerable efforts have been made to maximize drug efficiency and at the same time minimize side effects. As there is a great interpatient variability in response to chemotherapy, the development of predictive biomarkers is an ambitious aim for the rapidly growing research area of personalized molecular medicine. The individual prediction of response will improve treatment and thus increase survival and life quality of patients. In the past, cell cultures were used as in vitro models to predict in vivo response to chemotherapy. Several in vitro chemosensitivity assays served as tools to measure miscellaneous endpoints such as DNA damage, apoptosis and cytotoxicity or growth inhibition. Twenty years ago, the development of high-throughput technologies, e.g. cDNA microarrays enabled a more detailed analysis of drug responses. Thousands of genes were screened and expression levels were correlated to drug responses. In addition, mutation analysis became more and more important for the prediction of therapeutic success. Today, as research enters the area of -omics technologies, identification of signaling pathways is a tool to understand molecular mechanism underlying drug resistance. Combining new tissue models, e.g. 3D organoid cultures with modern technologies for biomarker discovery will offer new opportunities to identify new drug targets and in parallel predict individual responses to anticancer therapy. In this review, we present different currently used chemosensitivity assays including 2D and 3D cell culture models and several -omics approaches for the discovery of predictive biomarkers. Furthermore, we discuss the potential of these assays and biomarkers to predict the clinical outcome of individual patients and future perspectives.

MiR-218 impairs tumor growth and increases chemo-sensitivity to cisplatin in cervical cancer

MicroRNAs are noncoding RNA molecules of 18–25 nucleotides that regulate gene expression at the post-transcriptional levels. Recent data revealed that miR-218 played key roles in tumor metastasis. Here, we described the regulation and function of miR-218 in cervical cancer. Overexpression of miR-218 reduced the proliferation of the human cervical cancer cell line HeLa and induced cell apoptosis through the AKT-mTOR signaling pathway. In addition, it forced expression of miR-218 suppressed tumor growth in the orthotopic mouse model of HeLa cells. Furthermore, miR-218 increased chemosensitivity to cisplatin (CDDP) in vitro. Our results indicated that targeting miR-218 may provide a strategy for blocking the development of cervical cancer.

Chemotherapy for malignant gliomas based on histoculture drug response assay : a pilot study

OBJECTIVE

The Histoculture Drug Response Assay (HDRA), which measures chemosensitivity using minced tumor tissue on drug-soaked gelfoam, has been expected to overcome the limitations of in vitro chemosensitivity test in part. We analyzed interim results of HDRA in malignant gliomas to see if the test can deserve further clinical trials.

METHODS

Thirty-three patients with malignant gliomas were operated and their tumor samples were examined for the chemosensitivity to 10 chosen drugs by HDRA. The most sensitive chemotherapy regimen among those pre-established was chosen based on the number of sensitive drugs or total inhibition rate (IR) of the regimen. The response was evaluated by 3 month magnetic resonance image.

RESULTS

Among 13 patients who underwent total resection of the tumor, 12 showed no evidence of disease and one patient revealed progression. The response rate in 20 patients with residual tumors was 55% (3 complete and 8 partial responses). HDRA sensitivity at the cut-off value of more than one sensitive drug in the applied regimen showed a sensitivity of 100%, specificity of 60% and predictability of 70%. Another cut-off value of >80% of total IR revealed a sensitivity of 100%, specificity of 69%, and predictability of 80%. For 12 newly diagnosed glioblastoma patients, median progression-free survival of the HDRA sensitive group was 21 months, while that of the non-sensitive group was 6 months (p=0.07).

CONCLUSION

HDRA for malignant glioma was inferred as a feasible method to predict the chemotherapy response. We are encouraged to launch phase 2 clinical trial with chemosensitivity on HDRA.

22-oxa-1,25-dihydroxyvitamin D3 efficiently inhibits tumor growth in inoculated mice and primary histoculture of cholangiocarcinoma

BACKGROUND

It is well known that 1α,25-Dihydroxyvitamin D3 (1,25[OH]2 D3) restrains cell proliferation and induces differentiation and apoptosis in normal and tumor cells. The authors of this report recently demonstrated that 1,25(OH)2 D3 effectively inhibits the proliferation of cholangiocarcinoma (CCA) cell lines. The antitumor activity and the underlying mechanism of 22-oxa-D3, an analog of vitamin D, in mice and in tissue cultures from patients with CCA were further explored in the current study.

METHODS

Cell growth and cell cycle distribution were examined in CCA cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. Mice were injected subcutaneously with 4×10(6) CCA cells at both flank sides and intraperitoneal injections with phosphate-buffered saline or 22-oxa-D3 (15 μg/kg/day) for 17 days thereafter. Tumors were removed the next day. The expression levels of cyclin D1 and the cyclin-dependent kinase inhibitor p21 were determined by Western blot analysis and immunohistochemistry. Growth inhibition of 22-oxa-D3 in fresh tissue samples from patients with CCA was analyzed by using a histodrug response assay.

RESULTS

22-oxa-D3 effectively suppressed the growth of CCA cell lines in a time-dependent and dose-dependent manner. 22-oxa-D3 arrested CCA cells at G1 phase to S phase by the suppression of cyclin D1 expression and the up-regulation of p21. Supplementation of 22-oxa-D3 to CCA-inoculated mice significantly inhibited tumor growth without hypercalcemia or serious side effects. The treatment also induced cellular apoptosis in tissue samples from patients with CCA.

CONCLUSIONS

22-oxa-D3 effectively suppressed tumor growth in CCA-inoculated mice and induced cellular apoptosis in tissue samples from patients with CCA. The current data encourage further investigation of 1,25(OH)2 D3 or its analogues as therapeutic agents in the treatment of patients with CCA.

Evaluation of novel histone deacetylase inhibitors as therapeutic agents for colorectal adenocarcinomas compared to established regimens with the histoculture drug response assay

BACKGROUND AND AIMS

This study was to evaluate the efficacy of histone deacetylase (HDAC) inhibitors in colorectal cancer together with other established regimens.

MATERIALS AND METHODS

Chemosensitivities of 114 colorectal cancer patients to established regimens (fluorouracil (5-FU with leucovorin (FL), capecitabine, FL with irinotecan (FLIRI), and FL with oxaliplatin (FLOX)) as well as five hydroxamic acid derivatives (suberoylanilide hydroxamic acid, PXD101, and three novel candidates of CG-1, CG-2, and CG-3) were comparatively evaluated using the histoculture drug response assay.

RESULTS

The chemosensitivity with established regimens was between 34.2% and 52.6%, when the cutoff value of the inhibition ratio was set at 30%, and between 54.5% and 84.1% with HDAC inhibitors. All HDAC inhibitors displayed synergistic effects in combination with established regimens of FLOX and FLIRI (P < or = 0.0001-0.002). Advanced T- and N-category tumors and patients with synchronous adenoma displayed higher chemosensitivity to CG-3, CG-2, and CG-1, respectively, on a multivariate analysis (P = 0.023, 0.044, and 0.045, respectively). Tumors with mismatch repair defects were closely correlated with chemosensitivities to combined regimens of PDX101 with FLOX and FLIRI (P = 0.044 and 0.048, respectively).

CONCLUSIONS

Our findings firstly demonstrated the chemo-responsiveness of colorectal cancers to HDAC inhibitors with therapeutic efficacy comparable to the established regimens. Additionally, tumor growth and heredity were significantly associated with specific regimens, supporting their possible role as chemosensitive predictors.

Viability analysis and apoptosis induction of breast cancer cells in a microfluidic device: effect of cytostatic drugs

Breast cancer is the leading cause of cancer deaths among non-smoking women worldwide. At the moment the treatment regime is such that patients receive different chemotherapeutic and/or hormonal treatments dependent on the hormone receptor status, the menopausal status and age. However, in vitro sensitivity testing of tumor biopsies could rationalize and improve the choice of chemo- and hormone therapy. Lab-on-a-Chip devices, using microfluidic techniques, make detailed cellular analysis possible using fewer cells, enabling working with a patients’ own cells and performing chemo- and hormone sensitivity testing in an ex vivo setting. This article describes the development of two microfluidic devices made in poly(dimethylsiloxane) (PDMS) to validate the cell culture properties and analyze the chemosensitivity of MCF-7 cells (estrogen receptor positive human breast cancer cells) in response to the drug staurosporine (SSP). In both cases, cell viability was assessed using the life-stain Calcein-AM (CAAM) and the death dye propidium iodide (PI). MCF-7 cells could be statically cultured for up to 7 days in the microfluidic chip. A 30 min flow with SSP and a subsequent 24 h static incubation in the incubator induced apoptosis in MCF-7 cells, as shown by a disappearance of the aggregate-like morphology, a decrease in CAAM staining and an increase in PI staining. This work provides valuable leads to develop a microfluidic chip to test the chemosensitivity of tumor cells in response to therapeutics and in this way improve cancer treatment towards personalized medicine.

A synthetic retinoid, TAC-101 (4-[3,5-bis (trimethylsilyl) benzamido] benzoic acid), plus cisplatin: potential new therapy for ovarian clear cell adenocarcinoma

OBJECTIVE

A novel retinoid, TAC-101 (4-[3,5-bis (trimethylsilyl) benzamido] benzoic acid), induces apoptosis of ovarian clear cell adenocarcinoma. The antitumor effect of TAC-101 alone or combined with cisplatin was tested using human ovarian carcinoma.

METHODS

Induction of genes related to apoptosis by TAC-101 or cisplatin was assessed by DNA microarray analysis. TAC-101 (8 mg/kg/day orally for 21 days), cisplatin (7 mg/kg intravenously on day 1), or a combination of both drugs at the same dosages was administered to nude mice implanted subcutaneously with RMG-I or RMG-II clear cell adenocarcinoma cells. The antitumor effect was evaluated by calculating the treated/control tumor volume ratio at 21 days after implantation. The histoculture drug response assay was also performed using fresh surgical specimens of human ovarian cancer to determine the 50% inhibitory concentration (IC50).

RESULTS

Different apoptosis-related genes were induced by TAC-101 and cisplatin. Compared with control mice, the volume of both RMG-I and RMG-II tumors was significantly reduced (p<0.05) by either drug. The IC50 values of cisplatin and TAC-101 showed a significant correlation (p<0.01).

CONCLUSION

These in vitro findings suggest that a combination of TAC-101 and cisplatin may be a potential new treatment for ovarian clear cell adenocarcinoma.

Methylation of Ras association domain family protein 1, isoform A correlated with proliferation and drug resistance in hepatocellular carcinoma cell line SMMC-7721

BACKGROUND

It has been proposed that aberrant DNA methylation can alter cancer's response to therapeutic agents. The purpose of the present study was to investigate the relationship between Ras association domain family protein 1, isoform A (RASSF1A) and drug resistance or growth of hepatocellular carcinoma cell line SMMC-7721.

METHODS

Methylation status of RASSF1A from genomic gene of SMMC-7721 was determined with methylation-specific polymerase chain reaction and was further verified by demethylation treatment with 5-aza-2'-deoxycytidine. Wild-type RASSF1A cDNA was introduced into SMMC-7721; chemosensitivity to cisplatin, mitomycin and fluorouracil were analyzed using 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide assay. Growth of cells was detected by colony formation assay and xenograft model.

RESULTS

RASSF1A was inactivated in SMMC-7721 cell line through epigenetic hypermethylation, and reintroduction of RASSF1A was markedly able to reduce the resistance to some anticancer drugs and inhibit the growth of cancer cells either in vitro or in vivo.

CONCLUSION

These results correlate methylation status of RASSF1A with biological profiles of SMMC-7721 and thus, associate methylation with cancer therapy. RASSF1A may be useful to predict treatment response and help to develop novel treatment strategies for clinical treatment of hepatocellular carcinoma.

Sensitivity to cisplatin determined by the histoculture drug response assay and clinical response of endometrial cancer

This study investigated the value of the in vitro histoculture drug response assay (HDRA) for predicting the efficacy of chemotherapy in patients with endometrial cancer. Specimens were obtained from 115 patients with endometrial cancer treated at Keio University Hospital between 1994 and 2002. Tumor fragments were cultured on collagen sponge gel with cisplatin for 7 days, and cell viability was assessed. The cutoff value of the 50% inhibitory concentration of cisplatin was set at 23 microg/mL. Sensitivity of stage III or IV disease to chemotherapy was investigated, and differences of 5-year progression-free survival between patients with sensitive and resistant tumors were evaluated by the Kaplan-Meier method. Tumors were evaluable in 93.0% of patients (107/115). Among 38 patients in stages III or IV, 23 received chemotherapy containing cisplatin. Seven sensitive tumors did not recur, while recurrence/progression occurred within 6 months in 8/16 patients with tumors showing low sensitivity. Among stages III and IV patients, there was a significant difference of 5-year progression-free survival (P < 0.05) between those with tumors showing high or low sensitivity. Accordingly, the HDRA may predict the efficacy of chemotherapy for endometrial cancer.