ESTRO 36 Abstract Book

S963 ESTRO 36 2017 _______________________________________________________________________________________________

Clinical Oncology, Edinburgh, United Kingdom 2 Western General Hospital- Edinburgh Cancer Centre, medical Physics, Edinburgh, United Kingdom Purpose or Objective To assess if the target coverage and dose to organs at risk (OARs) from a vaginal vault brachytherapy CT plan are representative of dose delivered during the actual treatment. Material and Methods 28 patients scheduled for post-operative vaginal vault brachytherapy had an initial planning CT scan (CT1) done a few days before the first fraction, with the vaginal cylinder in-situ to generate a treatment plan. The PTV was the cranial 4cm of the vagina to a depth of 0.5cm, and the OARs outlined included the rectum, sigmoid, small bowel and bladder. On the day of the first fraction the patients has a second CT scan with the vaginal cylinder (CT2) and the PTV and OARs were outlined. Then the plan from CT1 was superimposed on CT2 to assess for variation in V100 and d90 to the PTV and the d2cc to the OARs. Prescribed dose was 21Gy in 3 fractions to the PTV, aiming for a V100 of >95% and d90 of 7Gy per fraction. Results Total of 56 scans were analysed. Mean PTV V100 for CT1: 95.8% (range 99.6% - 83.2%); CT2: 96% (range 99.8% – 90%). Mean d90 for CT1: 7.4Gy( range 7.8 – 6.7Gy); CT2: 7.3Gy (range 7.9 – 6.3Gy). Mean difference in d90 per fraction was 0.23 Gy per fraction (range: 0.56 – 0.01Gy).

radiotherapy and HDR brachytherapy, from 2008 to 2014 inclusive was performed. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method. Results A total of 76 patients were treated with radical radiotherapy incorporating HDR brachytherapy during this time period. The median age was 47 years with a median follow-up of 38 months. The histology was squamous cell carcinoma in 88% and adenocarcinoma in 11%. The distribution according to stage was as follows: stage I 16%, stage II 38%, stage III 40% and stage IV 5%. All patients received weekly Cisplatin chemotherapy with a median of 5 cycles delivered. The median dose of external beam radiotherapy was 45Gy delivered in 25 fractions over 5 weeks. The median brachytherapy dose was a total of 24Gy in 3 weekly fractions of 8Gy. The 5-year OS and PFS rates were 74% and 63% respectively. The 5-year locoregional control rate was 82%. There were a total of 25 failure and 12 of these had a component of local failure. However, only 3 of these had exclusively local failure. Of note is that the majority of patients with recurrences had a component of distant failure (19/25; representing 77% of relapses). Using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v.4.0), it appears as though severe acute (Grade 3/4) Gastrointestinal (GI) and Genitourinary (GU) toxicity was present in approximately 21% of patients, along with Grade 3/4 Hematologic toxicity seen in 34%. These results are similar to the published literature and compare favorably with our previous LDR brachytherapy There has been a shift towards incorporation of HDR brachytherapy world-wide in the management of cervix cancer and our institutional experience indicates that long-term outcomes for patients remain good, with generally high rates of local control. EP-1778 Combined intracavitary-interstitial IGABT of cervical cancer –First dosimetric experience in Hungary G. Fröhlich 1 , J. Vízkeleti 1 , N.N. Anhhong 1 , N. Mészáros 1 , T. Major 1 , C. Polgár 1 1 National Institute of Oncology, Centre of Radiotherapy, Budapest, Hungary Purpose or Objective Dosimetric evaluation of combined intracavitary- interstitial high-dose-rate image-guided adaptive brachytherapy (IGABT) of cervical cancer, implemented in Hungary. Material and Methods Since April 2016, 9 patients with cervical cancer were treated with overall 22 fractions of combined intracavitary-interstitial IGABT. After transrectal US- guided implantation of Utrecht or Fletcher applicator and needles, High-Risk-CTV (HR-CTV), bladder (b), rectum (r) and sigmoid (s) were contoured on CT, based on the post- teletherapy MRI of the patients. Dose-volume criterions of treatment plans were based on the recommendations of GEC-ESTRO Gyn WG. Treatment plans were compared to the conventional intracavitary 2D plans (the dose was prescribed to point A) and to CT-based 3D optimized plans (without needles) with Friedman and Kruskal-Wallis ANOVA and Spearman rank correlation tests. Results Median number of implanted needles was 3 (range: 2-4), mean volume of HR-CTV was 39.8 cm 3 (8.3-100.2 cm 3 ). For intracavitary-interstitial IGABT, intracavitary 2D and intracavitary 3D optimized plans, difference was found almost in all dose-volume parameters: V100 were 90.4%, 83% and 87.1% (p=0.043), DHI were 0.34, 0.30 and 0.27 (p=0.0137), D2(b) were 4.8 Gy, 6.9 Gy and 5.9 Gy (p<001), D2(r) were 3.3 Gy, 6.6 Gy and 3.5 Gy (p<0.001), D2(s) were experience. Conclusion

Small Bowel Sigmoid Rectum Bladder

3.16 (range 7.0 3.18 (range 6.8 0.3)

4.1 (range 6.4 - 1.9) 3.8 (range 5.9 - 1.4)

5.5 (rnage 7.0 - 3.9) 5.6 (range 7.1 - 3.6)

6.0 (range 6.7 - 4.9) 6.0 (range 7.2 - 4.9)

Mean d2cc (Gy) CT1

-

Mean d2cc (Gy) CT2

-

0.3)

Man difference in d2cc between CT1 and CT2

0.8

0.7

0.9

0.5

Conclusion The variation in d2cc doses when using the initial CT plan on the second scan taken on the day of the first fraction were minimal and not clinically significant. Differences in PTV coverage are mostly due to slight differences in PTV outlining mainly because of changes in the angle of the cylinder compared to the treatment couch. There does not appear to be the need to plan every single fraction for post-operative vaginal vault brachytherapy as the dosimetry using the initial plan was representative of the dose delivered on the day of treatment. EP-1777 Cervical cancer outcomes in the high-dose- rate brachytherapy era: A single institution experience N. Alyamani 1 , G. Bhattacharya 1 , R. Samant 1 , C. E 1 , T. Le 1 , K. Lupe 1 1 The Ottawa Hospital Regional Cancer Centre, Radiation Oncology, Ottawa, Canada¨ Purpose or Objective Since 2008, the management of cervix cancer with primary radiotherapy at our institution has included the use of HDR (high-dose-rate) brachytherapy; prior to this, LDR (low- dose-rate) brachytherapy was used. The aim of this study is to review our experience with HDR brachytherapy and to evaluate patient outcomes. Material and Methods A retrospective review of cervical cancer patients treated with curative intent using radical external beam