An International Radiosurgery Consortium Survey for Gynecological Stereotactic Ablative Radiation Therapy

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Stereotactic Ablative Radiotherapy (SABR) has been shown to be a highly effective treatment that improves local control in many disease sites. However, the role of SABR in gynecological cancers (GYN) has not been well-established. We hypothesize that there exists considerable variation in GYN SABR practice and technique among institutions. The goal of this study is to determine clinical and technical factors in utilization of GYN SABR among 11 experienced radiation oncologists. A comprehensive 63 question survey on GYN SABR was sent out to 11 radiation oncologists who have published original research, conducted clinical trials or have an established GYN SABR program at their institutions in 5 different countries. Issues addressed were clinical factors, indications, technique, dose and systemic therapy considered in SABR. Responses were combined and analyzed at a central institution. Most respondents indicated that salvage therapy for nodal (82%) and primary recurrent disease (91%) could be considered standard options for SABR in the setting of inability to administer brachytherapy. All other indications should be considered on clinical trials. Most would not use SABR as a boost in primary treatment unless a patient has absolute contraindications to brachytherapy or on clinical trial. Multi-modality imaging is often (91%) used for planning including PET, CT contrast and MRI. Bladder protocols and fiducial markers are common (82%) in set-up protocols. There is a wide variation for OAR tolerances however small bowel is considered the dose-limiting structure for most experts (91%). Fractionation schedules range from 3-6 fractions for definitive and boost SABR. For boost treatments, total EQD2 range from 64 Gy to 85 Gy, when prescribing to a CTV. 73% of respondents would treat chemotherapy sequentially after SABR with at least a 1 week break. Although SABR has becoming increasingly standard in other oncology disease sites, there remains a wide variation in both clinical and technical factors when treating GYN cancers. Nodal and recurrent disease is considered a potential indication for SABR whereas other indications should be offered on clinical trials. There is interest in incorporating SABR in GYN tumors in combination with sequential chemo especially in the recurrent and salvage setting. Further studies are warranted to establish consensus guidelines for GYN SABR treatment.