affiliation not provided to SSRN, affiliation not provided to SSRN, Erasmus University Medical Center Rotterdam - Erasmus MC Cancer Institute, University Medical Center Utrecht - Department of Radiation Oncology, Institute Verbeeten - Department of Radiation Oncology, Radiotherapiegroep, Isala Zwolle, affiliation not provided to SSRN, affiliation not provided to SSRN, Netherlands Cancer Institute, affiliation not provided to SSRN, Catharina Hospital, Haaglanden Medical Center, Maastricht University - Department of Radiation Oncology (MAASTRO), University of Groningen - Department of Obstetrics and Gynecology, Leiden University Medical Centre - Department of Obstetrics and Gynaecology, affiliation not provided to SSRN, affiliation not provided to SSRN, Leiden University - Department of Radiation Oncology and Leiden University - Department of Radiation Oncology