ESTRO 38 Abstract book

S1179 ESTRO 38

Coverage of CTV and dose to organ at risk (OAR) was reported in table 1, along with the dosimetric parameters of PDR BT employing other applicators. Apart from manageable acute genitourinary and gastrointestinal toxicities (2 patients with RTOG grade 1), no complications grade ³ 2 were reported.

Conclusion The initial experience revealed that BT treatment with Venezia TM was well-tolerated and allows for adequate tumor coverage while satisfying the dose constraints for OARs. It also appears user friendly in positioning and removal time. A larger cohort of patients will be required for additional conclusions related to the long-term clinical benefits and late toxicity. EP-2132 Verification of vaginal cylinder position using bony landmarks M. Zahra 1 , P. Drewell 1 , W. Keough 1 1 Edinburgh Cancer Centre, Oncology, Edinburgh, United Kingdom Purpose or Objective To allow rapid assessment at time of treatment of the correct positioning of the vaginal cylinder using bony landmarks Material and Methods A cohort of patients who had planning CT scans for their adjuvant post-hysterectomy vaginal vault brachytherapy also had a verification scan to assess the position of the organs at risk. These scans were reviewed and the distances between the position of the tip of the cylinder and S1 vertebra, the most proximal surface of the pubic bones and left and right femoral heads were measured using the planning software. The bladder volumes, the amount of soft tissue cranial to the cylinder and the angle of the cylinder to the treatment couch were also measured for each scan. Descriptive statistics along with differences in the measurements between the 2 scans, using T-test for 2 samples (2-tailed testing with p≤ 0.05 for significance) were assessed. Correlations between differences in the bladder volumes and cylinder angle with the differences in the measurements were studied using a Pearson correlation test (p≤ 0.05). Results 37 patients having had 2 CT scans were available for review.

Conclusion Although optimization improves the quality of intracavitary BT plans, interstitial plans yield in significantly higher dose coverage of HR-CTV and lower doses to OARs. IMAT plans decrease dose to the rectum. The impact of BT technique for summarised biological total dose of HR-CTV and critical organs is much higher than that of TT. Based on the personalised biological dose integration method, UDC overestimates OARs doses. EP-2131 Venezia: New Advanced Brachytherapy Gynecological Applicator in cervical cancer. Our preliminary data G. Riva 1 , V. Andrea 1 , R. Spoto 1 , S. Durante 1 , D. Ciardo 1 , S. Comi 2 , F. Cattani 2 , R. Lazzari 1 , B.A. Jereczek-Fossa 1 1 Istituto Europeo di Oncologia - IEO, Radiotherapy, MIlan, Italy; 2 Istituto Europeo di Oncologia - IEO, Medical Physics, MIlan, Italy Purpose or Objective The purpose of this work is to report our recent and preliminary experience with Elekta's Advanced Gynecological Applicator, Venezia™, a new applicator system that allows clinicians to treat different stages of cervical cancer as a hybrid brachytherapy (BT) applicator, combining characteristics of both ring and ovoid devices, with the possibility to perform interstitial BT. Material and Methods Clinical data, BT parameters and acute toxicity (Radiation Therapy Oncology Group RTOG toxicity scale) of consecutive women treated in our institute with Venezia TM were examined. Pulsed-dose-rate (PDR) was the technique chosen for all the patients. Clinical Target Volume (CTV) coverage and mean dose (D 2cm 3 ) to 2cm 3 of bladder, rectum and bowel were assessed. The dosimetric parameters of a series of 10 consecutive patients treated previously at our center with interstitial PDR BT employing other applicators (MUPIT and Utrecht, unpublished data) served as a dosimetry benchmark for the Venezia TM patients. Two- sided Wilcoxon rank sum test.was performed for statistical comparison Results Since January 2018 to May 2018, 8 women, median age 51 years (27.2-64.2) affected by cervical cancer were treated with Venezia™. All but one underwent interstitial BT. Median dose prescribed to CTV was 30 Gy (range 30-35) with a median dose rate of 0.6 Gy/h (range 0.5 - 0.6).

There was no significant difference between the 2 scans for the measurements done, T-test values for S1 -0.69 (p=0.48), pubic bone 1.05 (p=0.29), right -0.13 (p=0.89) and left -0.16 (p=0.87), showing a good degree of reproducibility in the cylinder insertions. There were 2