Objective: In the differential diagnosis between uterine fibroids and uterine sarcomas, realworld magnetic resonance imaging (MRI) diagnostic information is scarce; furthermore, high diagnostic sensitivity is important in clinical practice. We previously developed a diagnostic algorithm to detect uterine sarcoma with high sensitivity using simple MRI images and serum lactate dehydrogenase (LDH) levels. In this multicenter study, we investigated the preoperative diagnosis of sarcoma in the real world and further validated the usefulness of our diagnostic algorithm. Methods: Of 154 uterine sarcomas and 154 uterine fibroids treated at 15 centers between January 2006 and December 2020, 139 sarcomas (16 smooth muscle tumors of uncertain malignant potential) and 141 fibroids with diffusion-weighted imaging information were included in the analysis. The diagnostic algorithm was validated by 3 radiologists who were blinded to the clinical information and pathologic diagnoses and who read the MRIs. Results: The sensitivity/specificity of preoperative diagnosis was 77.7%/92.9% for the preoperative report; 92.1%/72.3% for algorithm A; and 82.0%/85.8% for algorithm B (McNemar’s test p<0.05). Comparison of overall survival rates among 3 groups (Group 1: negative A, Group 2: positive A and negative B; Group 3: positive B) using algorithms A and B showed p=0.012. On multivariate analysis, stage, and serum LDH level were independent prognostic factors. Conclusion MRI is useful for preoperative diagnosis of uterine sarcoma, and the sarcoma diagnostic algorithm presented in this study is an option for diagnosing sarcoma with greater sensitivity. This information should be shared with patients.

Background: Fertility preserving therapy using medroxyprogesterone acetate (MPA) is an important option for young patients with endometrial cancer or atypical endometrial hyperplasia (AEH). However, the effectiveness and feasibility of repeated MPA therapy for patients with intrauterine recurrence following initial MPA therapy is controversial. Only a few single-institution retrospective studies have been conducted on repeated MPA therapy, therefore, multicenter prospective studies for repeated MPA therapy are highly needed.The aim of this study is to assess whether repeated MPA therapy is effective and feasible for patients with intrauterine recurrence following initial MPA therapy. Methods This is a prospective, single-arm, a multicenter phase II trial on repeated MPA therapy for intrauterine recurrence following fertility-preserving therapy for AEH or stage IA (the International Federation of Gynecology and Obstetrics [FIGO] 2008) non-myoinvasive endometrioid carcinoma grade 1. Patients are treated with oral MPA (500–600 mg/day).Pathologically assessment via dilation and curettage will be performed every 2 months until complete response. The major inclusion criteria are 1) intrauterine recurrence of AEH or stage IA (FIGO 2008) endometrioid carcinoma grade 1 without myometrial invasion or extrauterine spread confirmed by imaging tests after complete remission with the previous MPA therapy. 2) The number of recurrences should be up to twice. 3) histologically diagnosed as AEH or endometrioid carcinoma grade 1, 4) 20–42 years of age, and 5) strong desire and consent for fertility-sparing treatment. The primary endpoint is 2-year recurrence-free survival rate. A total of 115 patients will be enrolled from multiple institutions in Japan and Korea within 4 years and followed up for 2 years.

Objective: Hospital treatment volume affects survival in patients with endometrial cancer;notably, initial treatment at high-volume centers improves survival outcomes. Our study assessed the effect of hospital treatment volume on cost-effectiveness and survival outcomes in patients with endometrial cancer in Japan. Methods: A decision-analytic model was evaluated using the following variables and their impact on cost-effectiveness: 1) hospital treatment volume (low-, intermediate-, and highvolume centers) and 2) postoperative recurrent risk factors based on pathological findings (high- and intermediate-risk or low-risk). Data were obtained from the Japan Society of Obstetrics and Gynecology database, systematic literature searches, and the Japanese Diagnosis Procedure Combination database. Quality-adjusted life years (QALY) was used as a measure of effectiveness. The model was built from a public healthcare perspective and the impact of uncertainty was assessed using sensitivity analyses. Results: A base-case analysis showed that the incremental cost-effectiveness ratio at high-volume centers was below a willingness-to-pay (WTP) threshold of ¥5,000,000with a maximum of ¥3,777,830/4.28 QALY for the high- and intermediate-risk group, and ¥2,316,695/4.57 QALY for the low-risk group. Treatment at the high-volume centers showed better efficiency and cost-effectiveness in both strategies compared to intermediate- or lowvolume centers. Sensitivity analyses showed that the model outcome was robust to changes in input values. With the WTP threshold, treatment at high-volume centers remained cost-effective in at least 73.6% and 78.2% of iterations for high- and intermediate-risk, and lowrisk groups, respectively. Conclusion Treatment at high-volume centers is the most cost-effective strategy for guiding treatment centralization in patients with endometrial cancer.

Background: Fertility preserving therapy using medroxyprogesterone acetate (MPA) is an important option for young patients with endometrial cancer or atypical endometrial hyperplasia (AEH). However, the effectiveness and feasibility of repeated MPA therapy for patients with intrauterine recurrence following initial MPA therapy is controversial. Only a few single-institution retrospective studies have been conducted on repeated MPA therapy, therefore, multicenter prospective studies for repeated MPA therapy are highly needed.The aim of this study is to assess whether repeated MPA therapy is effective and feasible for patients with intrauterine recurrence following initial MPA therapy. Methods This is a prospective, single-arm, a multicenter phase II trial on repeated MPA therapy for intrauterine recurrence following fertility-preserving therapy for AEH or stage IA (the International Federation of Gynecology and Obstetrics [FIGO] 2008) non-myoinvasive endometrioid carcinoma grade 1. Patients are treated with oral MPA (500–600 mg/day).Pathologically assessment via dilation and curettage will be performed every 2 months until complete response. The major inclusion criteria are 1) intrauterine recurrence of AEH or stage IA (FIGO 2008) endometrioid carcinoma grade 1 without myometrial invasion or extrauterine spread confirmed by imaging tests after complete remission with the previous MPA therapy. 2) The number of recurrences should be up to twice. 3) histologically diagnosed as AEH or endometrioid carcinoma grade 1, 4) 20–42 years of age, and 5) strong desire and consent for fertility-sparing treatment. The primary endpoint is 2-year recurrence-free survival rate. A total of 115 patients will be enrolled from multiple institutions in Japan and Korea within 4 years and followed up for 2 years.

Objective: Hospital treatment volume affects survival in patients with endometrial cancer;notably, initial treatment at high-volume centers improves survival outcomes. Our study assessed the effect of hospital treatment volume on cost-effectiveness and survival outcomes in patients with endometrial cancer in Japan. Methods: A decision-analytic model was evaluated using the following variables and their impact on cost-effectiveness: 1) hospital treatment volume (low-, intermediate-, and highvolume centers) and 2) postoperative recurrent risk factors based on pathological findings (high- and intermediate-risk or low-risk). Data were obtained from the Japan Society of Obstetrics and Gynecology database, systematic literature searches, and the Japanese Diagnosis Procedure Combination database. Quality-adjusted life years (QALY) was used as a measure of effectiveness. The model was built from a public healthcare perspective and the impact of uncertainty was assessed using sensitivity analyses. Results: A base-case analysis showed that the incremental cost-effectiveness ratio at high-volume centers was below a willingness-to-pay (WTP) threshold of ¥5,000,000with a maximum of ¥3,777,830/4.28 QALY for the high- and intermediate-risk group, and ¥2,316,695/4.57 QALY for the low-risk group. Treatment at the high-volume centers showed better efficiency and cost-effectiveness in both strategies compared to intermediate- or lowvolume centers. Sensitivity analyses showed that the model outcome was robust to changes in input values. With the WTP threshold, treatment at high-volume centers remained cost-effective in at least 73.6% and 78.2% of iterations for high- and intermediate-risk, and lowrisk groups, respectively. Conclusion Treatment at high-volume centers is the most cost-effective strategy for guiding treatment centralization in patients with endometrial cancer.

Background: Fertility preserving therapy using medroxyprogesterone acetate (MPA) is an important option for young patients with endometrial cancer or atypical endometrial hyperplasia (AEH). However, the effectiveness and feasibility of repeated MPA therapy for patients with intrauterine recurrence following initial MPA therapy is controversial. Only a few single-institution retrospective studies have been conducted on repeated MPA therapy, therefore, multicenter prospective studies for repeated MPA therapy are highly needed.The aim of this study is to assess whether repeated MPA therapy is effective and feasible for patients with intrauterine recurrence following initial MPA therapy. Methods This is a prospective, single-arm, a multicenter phase II trial on repeated MPA therapy for intrauterine recurrence following fertility-preserving therapy for AEH or stage IA (the International Federation of Gynecology and Obstetrics [FIGO] 2008) non-myoinvasive endometrioid carcinoma grade 1. Patients are treated with oral MPA (500–600 mg/day).Pathologically assessment via dilation and curettage will be performed every 2 months until complete response. The major inclusion criteria are 1) intrauterine recurrence of AEH or stage IA (FIGO 2008) endometrioid carcinoma grade 1 without myometrial invasion or extrauterine spread confirmed by imaging tests after complete remission with the previous MPA therapy. 2) The number of recurrences should be up to twice. 3) histologically diagnosed as AEH or endometrioid carcinoma grade 1, 4) 20–42 years of age, and 5) strong desire and consent for fertility-sparing treatment. The primary endpoint is 2-year recurrence-free survival rate. A total of 115 patients will be enrolled from multiple institutions in Japan and Korea within 4 years and followed up for 2 years.

Objective: Hospital treatment volume affects survival in patients with endometrial cancer;notably, initial treatment at high-volume centers improves survival outcomes. Our study assessed the effect of hospital treatment volume on cost-effectiveness and survival outcomes in patients with endometrial cancer in Japan. Methods: A decision-analytic model was evaluated using the following variables and their impact on cost-effectiveness: 1) hospital treatment volume (low-, intermediate-, and highvolume centers) and 2) postoperative recurrent risk factors based on pathological findings (high- and intermediate-risk or low-risk). Data were obtained from the Japan Society of Obstetrics and Gynecology database, systematic literature searches, and the Japanese Diagnosis Procedure Combination database. Quality-adjusted life years (QALY) was used as a measure of effectiveness. The model was built from a public healthcare perspective and the impact of uncertainty was assessed using sensitivity analyses. Results: A base-case analysis showed that the incremental cost-effectiveness ratio at high-volume centers was below a willingness-to-pay (WTP) threshold of ¥5,000,000with a maximum of ¥3,777,830/4.28 QALY for the high- and intermediate-risk group, and ¥2,316,695/4.57 QALY for the low-risk group. Treatment at the high-volume centers showed better efficiency and cost-effectiveness in both strategies compared to intermediate- or lowvolume centers. Sensitivity analyses showed that the model outcome was robust to changes in input values. With the WTP threshold, treatment at high-volume centers remained cost-effective in at least 73.6% and 78.2% of iterations for high- and intermediate-risk, and lowrisk groups, respectively. Conclusion Treatment at high-volume centers is the most cost-effective strategy for guiding treatment centralization in patients with endometrial cancer.

Objective: We have established 4 histopathologic subtyping of high-grade serous ovarian cancer (HGSOC) and reported that the mesenchymal transition (MT) type has a worse prognosis than the other subtypes. In this study, we modified the histopathologic subtyping algorithm to achieve high interobserver agreement in whole slide imaging (WSI) and to characterize the tumor biology of MT type for treatment individualization. Methods: Four observers performed histopathological subtyping using WSI of HGSOC in The Cancer Genome Atlas data. As a validation set, cases from Kindai and Kyoto Universities were independently evaluated by the 4 observers to determine concordance rates. In addition, genes highly expressed in MT type were examined by gene ontology term analysis. Immunohistochemistry was also performed to validate the pathway analysis. Results: After algorithm modification, the kappa coefficient, which indicates interobserver agreement, was greater than 0.5 (moderate agreement) for the 4 classifications and greater than 0.7 (substantial agreement) for the 2 classifications (MT vs. non-MT). Gene expression analysis showed that gene ontology terms related to angiogenesis and immune response were enriched in the genes highly expressed in the MT type. CD31 positive microvessel density was higher in the MT type compared to the non-MT type, and tumor groups with high infiltration of CD8/CD103 positive immune cells were observed in the MT type. Conclusion We developed an algorithm for reproducible histopathologic subtyping classification of HGSOC using WSI. The results of this study may be useful for treatment individualization of HGSOC, including angiogenesis inhibitors and immunotherapy.

The development of new treatments for gynecological malignancies has been conducted mainly through collaborative international phase III trials led by the United States and Europe. The survival outcomes of many gynecological malignancies have greatly improved as a result. Recent large-scale genome-wide association studies have revealed that drug efficacy and adverse event profiles are not always uniform. Thus, it is important to validate new treatment options in each country to safely and efficiently provide newly developed treatment options to patients with gynecological malignancies. The Japanese Gynecologic Oncology Group (JGOG) is conducting 5 cohort studies (JGOG 3026, 3027, 3028, 3030, and 3031) to establish real-world data (RWD) of poly(ADP-ribose) polymerase (PARP) inhibitor use in patients with advanced or recurrent epithelial ovarian cancer. The RWD constructed will be used to provide newly developed PARP inhibitors for women with advanced or recurrent ovarian cancer in a safer and more efficient manner as well as to develop further treatment options. In 2022, The JGOG, Korean Gynecologic Oncology Group, Chinese Gynecologic Cancer Society, and Taiwanese Gynecologic Oncology Group established the East Asian Gynecologic Oncology Trial Group to collaborate with East Asian countries in clinical research on gynecologic malignancies and disseminate new knowledge on gynecologic malignancies from Asia. The JGOG will conduct a collaborative integrated analysis of the RWD generated from Asian countries and disseminate real-world clinical knowledge regarding new treatment options that have been clinically implemented.

Objective: Owing to the potential benefits of minimally invasive hysterectomy for endometrial cancer, the practice pattern has recently shifted in Japan. This study examined the trends in minimally invasive surgery (MIS) in patients with endometrial cancer in Japan. Methods: This retrospective observational study examined the Japan Society of Obstetrics and Gynecology Tumor Registry database between 2015–2019. This study examined the time-specific proportion change and predictors of MIS use in initial endometrial cancer treatment in Japan, and compared it with the use of abdominal surgery. Additionally, the association between hospital surgical treatment volume and MIS use was examined. Results: A total of 14,059 patients (26.5%) underwent minimally invasive hysterectomy, and 39,070 patients (73.5%) underwent abdominal hysterectomy in the study period. Patients who underwent MIS were more likely to be treated at high-volume centers, younger, central, or western Japan residents, registered in recent years, and had a tumor with stage I disease, type 1 histology, and less myometrial invasion (all adjusted p<0.05). The proportion of MIS treatments increased from 19.1% in 2015 to 34.3% in 2019 (p<0.001). On multivariable analysis, treatment at high-volume centers was a contributing factor for MIS (adjusted odds ratio=3.85; 95% confidence interval=3.44–4.30). MIS at high-volume centers increased significantly from 24.8% to 41.0% (p<0.001) during the study period, whereas MIS at low-volume centers remained at median 8.8%. Conclusion MIS has increased significantly in recent years, accounting for nearly 34% of surgical management of endometrial cancer in Japan. High-volume treatment centers take the lead in performing MIS.