1. Image Guided Interstitial Brachytherapy For Locally Advanced Gynaecological Cancer With A MUPIT Applicator M.A.D. Haverkort, MD 1, E. Van der Steen - Banasik, MD 1, C.G. Verhoef, MD PhD 2, A.L. Aalders, MD 3, M.P.R. Van Gellekom, PhD 1. 1 Department of Radiation Oncology, Radiotherapiegroep, Arnhem, The Netherlands, 2 Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, The Netherlands, 3 Department of Obstetrics and Gynecology, Rijnstate Hospital, Arnhem, The Netherlands. Primary or recurrent disease in the vagina from cervical, endometrial, or vulvar carcinoma are usually not amenable to curative organ-sparing surgery. Radiation therapy is currently the most widely used and effective primary treatment for patients with invasive vaginal cancers. Brachytherapy is an integral part of treatment for these tumors to ensure that a curative dose is given to the gross disease. Here we’ve assessed treatment outcome of image guided interstitial brachytherapy (BT) for locally advanced gynaecological cancer in Arnhem treated with external beam radiotherapy (EBRT) followed by BT using the Martinez Universal Perineal Interstitial Template (MUPIT). BACKGROUND & PURPOSE Data from all patients treated for locally advanced gynaecological tumours with EBRT and interstitial BT from 1999 till June 2015 were retrospectively collected. Treatment was initiated with whole pelvic EBRT followed by BT using the MUPIT. All implants were virtually pre-planned using CT and later MRI of the pelvis with a MRI compatible dummy MUPIT cylinder in situ. The high risk clinical target volume (HR-CTV) and the organs at risk (OAR) were contoured and a pre-plan for implantation was made. Within a week after EBRT the planned implantation was performed, under laparoscopic visualization if bowel was present close to the tumour. Final contouring and treatment planning were done using a post-implant CT (25 patients) and later MRI (13 patients). The planning aim of BT after manual dose optimization was to achieve a D90 > 70 Gy in the HR-CTV calculated as the total biologically equivalent to 2 Gy fractions of EBRT and BT (EQD2). The repair half time is assumed to be 1.5 hrs. MATERIALS & METHODS CONTACT INFORMATION Dorien Haverkort d.haverkort@radiotherapiegroep.nl Patient characteristics N= 38, mean age 70 yr (43-96) 21 primary vaginal cancer 10 recurrent endometrial cancer 7 other cancer (recurrent cervical or vulvar) Median follow up: 47 Months (2-162) Treatment Median EBRT dose: 46 Gy (22-50) Chemoradiation N=15 (40%) Brachytherapy 23 pat PDR-BT 40-48 hourly pulses median total dose 24 Gy (20-28,6) 15 pat HDR-BT three-daily pulses of 2,5 Gy median total dose 20 Gy (12,5-22,5) Mean HR-CTV D90 68,5 Gy (59,4-75) Mean number of needles: 14 (5-19) Median overall treatment time: 42 days (30-81) Toxicity ≥ grade 3 6 patients: skin atrophy (N=3) proctitis (N=2) hip osteonecrosis (N=1) No severe toxicity after MRI guided BT RESULTS Image guided interstitial BT for locally advanced primary vaginal or recurrent endometrial and cervical cancer results in an excellent 5 year local control rate of 92%. Image guided BT with MRI appears to be associated with less severe late toxicity. We aim to further improve the quality of our implants in terms of geometry (applicator and implantation technique issues) and homogeneity (planning issues), and to escalate the dose. CONCLUSIONS 5yr LC=92% Figure 1: The MUPIT applicator Figure 2: Laparascopic view of the implanted needles Figure 3: Dose distribution of a MRI guided treatment plan in transversal (left) and coronal view (right), with the HR-CTV delineated in dotted aquamarine. Figure 4: Kaplan Meier curves 5yr DFS= 70%5yr OS= 70%