Po10

Purpose Clinicians at Aarhus University Hospital, Denmark developed the individualized 3D printed needle templates and Varian worked with Aarhus to develop this hybrid applicator with standard needle template. We started using this in our practice in 2022 and present our initial experience using this Aarhus ring and tandem MR compatible hybrid interstitial applicator with both straight and oblique needles in patients with locally advanced cervical carcinoma. Materials & Methods A total number of 22 patients from stage IB3 to IIIB were treated with MR based Image guided adaptive brachytherapy between March 2022 to January 2023, of which 17 patients were treated with Hybrid Interstitial brachytherapy with Aarhus applicator after completion of External Beam Radiotherapy. All patients were treated with External Beam radiation to a dose of 45 to 50 Gy in 25 fractions with SIB (55 Gy) to gross nodes along with concurrent weekly chemotherapy with Cisplatin @40 mg/m2. This was followed by brachytherapy to a total dose of 21 - 28 Gy in 3 to 4 fractions of IGABT with planning aims of HRCTV - D90 to receive > 85 to 90 Gy and keeping the EQD2 for 2cc Rectum, Sigmoid and Bladder to < 65 - 70 Gy, 70 - 75 Gy and 80 -85 Gy respectively. Each patient had 2 insertions of brachytherapy with 1 to 2 fractions with each insertion, done under short General anesthesia using real time trans abdominal USG guidance. Results A total number of 62 fractions have been performed with a median number of 4 (range 1-5 needles per patient. 8 patients required oblique needles. The average time from insertion to the first fraction treatment was 4 hours. Six hours gap was given between the two fractions done on same day. No acute Grade 3 complications have been recorded including bleeding or organ perforation. The Median EQD2 D90 of HRCTV was 91.77 Gy [80.1 to 101.9 Gy] and Median GTVp dose D98 was 110.12 Gy [81.1 to 123.5 Gy]. Median EQD2 for 2cc Bladder was 77.75 Gy [65.48 to 80.73Gy], Rectum was 56.36 [40.76 to 66.39Gy], Sigmoid colon - 61.18 Gy [52.24 to 72.88Gy], Small bowel - 58.4 [51.98 to 63.42Gy] 12 out of 17 patients completed first follow up at 3 months, out of which 11 patients showed complete response at cervix. Conclusion Our initial results show excellent dosimetry and no significant procedure related complications with MRI based IGABT in our clinic using hybrid applicator. Clinicians at Aarhus University Hospital, Denmark developed the individualized 3D printed needle templates and Varian worked with Aarhus to develop this hybrid applicator with standard needle template. We started using this in our practice in 2022 and present our initial experience using this Aarhus ring and tandem MR compatible hybrid interstitial applicator with both straight and oblique needles in patients with locally advanced cervical carcinoma. A total number of 22 patients from stage IB3 to IIIB were treated with MR based Image guided adaptive brachytherapy between March 2022 to January 2023, of which 17 patients were treated with Hybrid Interstitial brachytherapy with Aarhus applicator after completion of External Beam Radiotherapy. All patients were treated with External Beam radiation to a dose of 45 to 50 Gy in 25 fractions with SIB (55 Gy) to gross nodes along with concurrent weekly chemotherapy with Cisplatin @40 mg/m2. This was followed by brachytherapy to a total dose of 21 - 28 Gy in 3 to 4 fractions of IGABT with planning aims of HRCTV - D90 to receive > 85 to 90 Gy and keeping the EQD2 for 2cc Rectum, Sigmoid and Bladder to < 65 - 70 Gy, 70 - 75 Gy and 80 -85 Gy respectively. Each patient had 2 insertions of brachytherapy with 1 to 2 fractions with each insertion, done under short General anesthesia using real time trans abdominal USG guidance. A total number of 62 fractions have been performed with a median number of 4 (range 1-5 needles per patient. 8 patients required oblique needles. The average time from insertion to the first fraction treatment was 4 hours. Six hours gap was given between the two fractions done on same day. No acute Grade 3 complications have been recorded including bleeding or organ perforation. The Median EQD2 D90 of HRCTV was 91.77 Gy [80.1 to 101.9 Gy] and Median GTVp dose D98 was 110.12 Gy [81.1 to 123.5 Gy]. Median EQD2 for 2cc Bladder was 77.75 Gy [65.48 to 80.73Gy], Rectum was 56.36 [40.76 to 66.39Gy], Sigmoid colon - 61.18 Gy [52.24 to 72.88Gy], Small bowel - 58.4 [51.98 to 63.42Gy] 12 out of 17 patients completed first follow up at 3 months, out of which 11 patients showed complete response at cervix. Our initial results show excellent dosimetry and no significant procedure related complications with MRI based IGABT in our clinic using hybrid applicator.