EP-1260: Comparison of 3D conformal radiotherapy and IMRT and the effect ofposition in locally advanced rectal cancer

ESTRO 33, 2014 biopsies 8 weeks after treatment completion. One patient, with a partial excision of the tumour prior to radiotherapy, experienced skin necrosis and deterioration of sphincter function and had to be surgically managed. All other patients, followed up to one year so far, had complete remission of RT related symptoms at 6 months. Patient reported late side-effects have been mild, with no proctitis, faecal incontinence, dyspareunia or pain, and only grade 1 diarrhea, erectile dysfunction and urinary incontinence. With a very short follow-up (median 1 year) no local or distant recurrences have been observed. Conclusions: In this small case series, high dose electron treatment seems to represent a viable alternative to traditional management of early stage anal cancers. The acute toxicity was much lower than what is usually observed for standard photon treatment. Treatment toxicity seems manageable, despite one patient (previously surgically treated in the area) experiencing skin necrosis. Quality of life after treatment completion was excellent, with low patient reported toxicity. Tumour control data is very preliminary, but at the time of reporting, all patients remain in remission. EP-1259 Abstract withdrawn EP-1260 Comparison of 3D conformal radiotherapy and IMRT and the effect of position in locally advanced rectal cancer O. Derinalp Or1, Y. Yukselen Guney2, B. Kucukplakci2, S. Aytac Arslan2, N. Kaplan2, O. Gul2, A. Gani2, A. Simsek Bozkurt2, E. Delikgoz Soykut2 1 Adana Numune Hospital, Department of Radiation Oncology, Ankara, Turkey 2 Ankara Oncology Hospital, Department of Radiation Oncology, Ankara, Turkey Purpose/Objective: In this study; the computed tomography (CT) simulation images of 30 locally advanced rectal cancer patients who had preoperative chemoradiotherapy (CRT) between May 2012 and November 2012 were used. Materials and Methods: Patients were simulated both prone and supine position. 3DCRT and IMRT plans were created in Precise Dicom 3.0 version and Hi-ART Tomotherapy Inverse Dicom 3.0 Treatment Planning System respectively. All patients treated with 3DCRT in prone position. Dosimetric outcome was compared for 3-field CRT (3FCRT), 4-field CRT(4FCRT) and IMRT technics by analysing DVHs. These planning techniques were compared using dosimetric descriptives which were obtained from the DVH. The PTV comparison parameters were Dmean, Dmin, and Dmax doses; D95,HI and monitor unit (MU). As organs at risk (OAR), Dmax, Dmean, V5, V15, V25, V45 for small bowel; Dmax, Dmean, V30, V40 for bladder and Dmax, Dmean, Dmin for bilateral femoral heads were evaluated. Results: For PTV Dmax was significantly higher with IMRT than with 4FCRT and there was no difference with 3FCRT in prone position. Dmax was significantly higher with IMRT than 3FCRT and 4FCRT. Dmean was significantly higher with IMRT both prone and supine position. HI was higher with IMRT than with 3FCRT, but lower than with 4FCRT for supine position. HI was equal for 3FCRT and 4FCRT and was better than with IMRT for prone position. D95 of IMRT in prone and supine position was significantly higher than both conformal technics . MU of IMRT was longer than 4FCRT, and 3FCRT, respectively. Dmean was higher in, other PTV parameters were higher in supine position and D95 did not change with position in 3 field technic. For 4FCRT and IMRT there was no difference in PTV parameters related to position except Dmin. It was significantly higher in supine position for IMRT. No statistically significant differences were seen between V25 and V45 values of small bowel for the three techniques in prone position. But Dmax, Dmean, V15 and V45 of IMRT were higher than CRTs. In supine position V25 and V45 of IMRT were statistically lower than CRT. V15 and V25 were statistically higher in supine position for three techniques. Also Dmax and V45for 3FCRT; V45 for 4FCRT and Dmean for IMRT were higher in supine position. Dmax for bladder was significantly higher, but Dmean V30 and V40 were significantly lower with IMRT. All parameters for bladder were significantly higher with 3DCRT in supine position and had no difference with 4DCRT according to position. V40 for bladder was significantly higher in supine, Dmin was significantly higher for prone position and all other parameters did not difference with IMRT. All parameters for femoral heads were statistically significantly with IMRT. Conclusions: Dosimetric results are compatible with the literature for 3DCRT and IMRT technics. altough dosimetry for OAR was better with IMRT, it is not standart treatment approach yet for rectal cancer. 3FCRT and 4FCRT results are similar.

S75 EP-1261 Local chemotherapy and conformal radiotherapy in treatment of the locally advanced pancreatic cancer G.L. Vasilev1, L.I. Korytova1, A.V. Pavlovskiy2, E.V. Vlasova1, S.A. Popov2 1 Russian Research Institute of Radiology and Surgery, Radiotherapy, Saint-Petersburg, Russian Federation 2 Russian Research Institute of Radiology and Surgery, Surgery, SaintPetersburg, Russian Federation Purpose/Objective: To evaluate efficiency of chemoradiotherapy with gemcitabine-based regimen in patients with locally advanced pancreatic adenocarcinoma. Materials and Methods: 16 patients with unresectable, histologically confirmed adenocarcinoma of the pancreatic head and body without distal metastases were included in our study. Treatment was provided in two stages. First stage: diagnostic angiography. Arteriafemoralis was punctured, catheter was fixed in arteria mesenterica superior and truncus coeliacus. After the diagnostics we provided local chemotherapy with gemcitabine 1000 mg/2 hours, via catheter placed in truncus coeliacus. Second stage: 3d conformal radiotherapy was delivered at the dose of 51 Gy in 17 fractions of 3 Gy per fractions, 5 days/week, over 3 weeks. We made patient-specific pad for each person. Quality of radiotherapy was checked by X-ray volume imaging (XVI). The patients were observed over a period of 6 – 12 months. Results: At the end of the observation period stable disease was documented in 6 patients, partial remission – 7 patients, of which 2 were restaged and operated. Three patients died. Pain syndrome was reduced in 5 patients. Side effects: leukopenia 1-2 stage – 2 patients, anaemia 12 stage – 4 patients, trombocytopenia 1-2 stage – 6 patients. Conclusions: Local chemotherapy with gemcitabine – 1000 mg and 3d conformal radiotherapy is a safe treatment, improves pain syndrome and increases quality of life. EP-1262 MRI-guided SBRT with individualised margins for locally advanced pancreatic cancer ñ a feasibility and safety study H.D. Heerkens1, M. Van Vulpen1, O. Reerink1, J.C.J. De Boer1, C.A.T. Van den Berg1, F.P. Vleggaar2, I.Q. Molenaar3, G.J. Meijer1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands 2 UMC Utrecht, Gastroenterology, Utrecht, The Netherlands 3 UMC Utrecht, Surgery, Utrecht, The Netherlands Purpose/Objective: Patients with locally advanced pancreatic cancer (LAPC) have a median survival of 8-14 months due to limited effective therapeutic options. Radiotherapy may delay the development of metastasis and physical discomfort, it may lead to a better palliation and possibly increase the median survival. We want to explore the safety and technical feasibility of MRI-guided stereotactic radiotherapy as a treatment option for these patients. Materials and Methods: 30 patients with LAPC without distant metastasis will be included in this study. A custom made abdominal corset is manufactured to reduce breathing induced tumour motion. In each patient, 4 gold fiducial markers are inserted during an endoscopic ultrasound procedure (2 Visicoils 0.35x10mm and 2 QLRAD markers 0.4x6mm). One week after marker placement, patients undergo a 4D treatment planning CT, MRI and cine MRI scanning with the corset. Delineation of the GTV and organs at risk is carried out on combined imaging modalities. Tumour motion is determined with cine MRI, as described earlier[1]. After treatment planning, the static dose distribution is convolved with the 3D motion trajectory to simulate and evaluate the delivered dose to the tumour and OARs. If necessary, treatment margins are adapted to individual tumour motion trajectories. Stereotactic irradiation is carried out up to a dose of 24 Gray in 3 fractions in one week. Position verification is performed online with 4D CBCTs, with 4D matching based on the marker positions at the midvent position.