Abstract Book

S821

ESTRO 37

The cause of non-surgery was morbid obesity in 86% of the cases. Median age was 70 years (57-89). Histology was endometrioid adenocarcinoma in all cases. The clinical stage was: I 72%, II 14% and III 14%. All patients received EBRT plus intracavitary brachytherapy whit UTRECHT applicator, in 71% of the cases guided by magnetic resonance imaging (MRI), and in remaining 29% a CT- The median dose EBRT 50 Gy (45-63) and HDR-BT 14 Gy (10-19,5), median dose per fraction of HDR-BT was 6 Gy (5-7). The median dose EBRT+HDR-BT expressed in total EQD2 (α/β=10) was 69,8 Gy (64,8-74,5), GTV D90 EQD2 (α/β=10) was 65,9 Gy (60-84,2). The median doses the risk organs (D2 cc) EQD2 (α/β=3) : bladder 72,8 Gy (68,8- 85,2), rectum 66,9 Gy (53,7-73,1) and sigma 65,4 Gy (52,3-74,3). With a median follow-up of 23 months all the patients are without evidence of disease. Complete response confirmed by MRI in 71% of the patients. Acute toxicity G1-2 in 57% of patients and late toxicity in 29% patients. One patient had G3 late toxicity (rectal bleeding). Conclusion Although the number of patients and folow-up is still very limited, EBRT plus HDR-BT, may be a treatment option for inoperable patients with good compliance and limited toxicity. EP-1515 Motion of the uterine tip during radiotherapy for cervical cancer is not correlated with survival A. Cree 1 , S. Morrison 2 , G. Price 1 , M. Van Herk 3 , A. McWilliam 1 , A. Choudhury 1 1 The Christie NHS Foundation Trust, Radiotherapy Related Research, Manchester, United Kingdom 2 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom 3 The University of Manchester, Radiotherapy Related Research, Manchester, United Kingdom Purpose or Objective Significant motion of the uterus and cervix occurs during external beam radiotherapy with variation between patients. A large CTV to PTV margin is used to account for this. Studies quantifying motion have small numbers with little about the implication of motion on patient outcome. This study aims to assess if patients with greater motion at the tip of the uterus have poorer overall survival. Material and Methods Patients treated with radical radiotherapy for cervical cancer were selected from an anonymised database with prospectively collected outcome data. 79 patients were identified with scans at 3 time points; pre-treatment MR, planning CT and on-treatment MR in the final week of treatment. Patients received external beam radiotherapy with a dose of 40/20Gy or 45/25Gy followed by brachytherapy or an external beam boost. No formal adaptive techniques were used and no patients were re- planned during treatment. The majority of patients had on–treatment cone beam CT, at least weekly, used for bony matching. All scans were fused with the initial MR using in-house software. The uterus and cervix complex were contoured by a single observer on a single sagittal slice identified as the midpoint on the initial MR. Points were identified, as seen in figure 1, to define different areas of the uterus and cervix with points 1, 2 and 7 representing the tip of the uterus. This was repeated for 5 patients to assess based planning HDR-BRT was delivered. Toxicity were evaluated by CTCAE v 4.0. Results

intra-observer variability. The mean difference in position was calculated at each point based on the planning scan to avoid systematic errors during treatment.

Results

Standard deviation (mm)

Median (mm)

Mean (mm)

Maximum (mm)

Point

1

19.8

24.1

14.9

88.6

2

16.7

20.3

12.7

76.5

7

20.3

22.6

11.8

71.9

Intra-observer variability was small with a mean difference of 2.5mm and standard deviation of 2mm. Median follow up was 23 months (range 6 -125). 14 patients have died with a 2 year overall survival of 80%. Survival analysis was performed using Kaplan-Meier analysis split at the median and confirmed using univariate cox regression analysis. There was no statistically significant association with survival.

Conclusion The median motion of the tip of the uterus exceeds the CTV to PTV margin implying inadequate CTV coverage of the uterus in a proportion of patients. However, there is no evidence that motion at the tip of the uterus is associated with survival. The study has a number of limitations including no assessment of lateral motion and the small number of events. Nevertheless, consistent findings were seen for points 1, 2 and 7. This is a novel method allowing assessment of cervix and uterus motion in a large patient cohort. Future work will include assessment the association between motion and toxicity. The hypothesis that dose to tip of the uterus does not associate with survival suggests that it may be possible to exclude the uterine fundus from the CTV, reducing toxicity without affecting overall survival. EP-1516 Phase I study of nimotuzumab plus concurrent IMRT and chemotherapy on cervical cancer A. Qu 1 , P. Wang 1 , M. Zhang 1 , P. Jiang 1 , X. Deng 1 , J. Wang 1 1 Peking Universit y Third Hospital, Radiation Oncology, Beijing, China