Ethics approval and consent to participate:
Ethics and publication of this study was approved by the Institutional Review Board of Shizuoka Cancer Center (Shizuoka, Japan) on December 10, 2015 (approval no.: T27-37-27-1-3). The board waived the requirement for informed written consent due to the anonymous nature of the data and the fact that this research presented no risk of exposure to the subjects.
Consent for publication:
Not applicable
Availability of data and materials:
All relevant data are within the paper. The dataset supporting the conclusions of this article is available from the corresponding author on reasonable request.
Competing interests: All authors declare that they have no competing interests.
Funding:
This work was supported in part by the National Cancer Center Research and Development Fund of Japan (29-A-3) and by the Japan Agency for Medical Research and Development (AMED, JP18ck0106222 and JPP19ck0106513). The funding body had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
Authors’ contributions:
MT, TK, RK, TT, HK, MI and NY planned and designed the study. MT, SM, WK, KH, MI, AS, AM, SN, SS, MM, SN, HT and YO carried out collecting data. FT performed the statistical analyses. MT contributed to writing of article. All authors have been involved in drafting the manuscript or revising it critically for important intellectual content and approved the final manuscript.
Acknowledgement:
To all members from the list of hospitals in supplementary Table A3, who registered their patients to this study, we would like to thank you all for your great efforts.
Author details
1Department of Gynecology, Shizuoka Cancer Center, 1007 Shimonagakubo, Nagaizumicho, Suntogun, Shizuoka 411-8777, Japan, 2Department of Information Science, Iwate Medical University, Idaidori, Yahabacho, Shiwagun, Iwate 028-3694, Japan, 3Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, 202 Yamadaoka, Suita, Osaka 565-0871, Japan, 4Department of Obstetrics and Gynecology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishiharacho, Nakagamigun, Okinawa 903-0125, Japan, 5Department of Gynecology, Saitama Cancer Center, 818 Komuro, Inamachi, Kitaadachigun, Saitama 362-0806, Japan, 6Department of Gynecology, Kanagawa Cancer Center, Nakaonaga, Asahiku, Yokohama, Kanagawa 241-0815, Japan, 7Department of Obstetrics and Gynecology, Faculty of Medicine, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8575, Japan, 8 Departments of Reproductive Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuoku, Chiba, Chiba 260-8677, Japan, 9Department of Gynecologic Cancer, Hyogo Cancer Center, 13-70 Kitaozicho, Akashi, Hyogo 673-8558, Japan, 10Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, 65 Tsurumaicho, Showaku, Nagoya, Aichi 466-8550, Japan, 11Department of Gynecology, Aichi Cancer Center Hospital, Kanokoden, Chikusaku, Nagoya, Aichi 464-8681, Japan, 12Department of Obstetrics and Gynecology, Kurume University School of Medicine, 67 Asahicho, Kurume, Fukuoka 830-0011, Japan, 13Department of Obstetrics and Gynecology, Tohoku University Hospital, Seiryo-machi, Aobaku, Sendai, Miyagi 980-8574, Japan, 14Department of Gynecology, Osaka International Cancer Institute, 3-1-69, Otemae, Chuoku, Osaka, Osaka 541-8567, Japan, 15Department of Obstetrics and Gynecology, Tokyo Metropolitan Bokutoh Hospital, 4-23-15 Kotobashi, Sumidaku, Tokyo 130-8575, Japan, 16 Department of Gynecology and Obstetrics, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aobaku, Sendai, Miyagi 981-8558, Japan, 17Radiation Therapy Center, Okinawa Chubu Hospital, 281 Aza-miyazato, Uruma, Okinawa 904-2293, Japan, 18Department of Obstetrics and Gynecology, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima, Kagoshima 890-8544, Japan, 19Department of Gynecology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuoku, Tokyo 104-0045, Japan.