PO-1029: Intra-fractional organ position variation evaluation during HDR intracavitary brachytherapy of cervical cancer

Z. Siavashpour, M.R. Aghamiri, R. Jaberi, H.R. Dehghan Manshadi
2015 Radiotherapy and Oncology  
Purpose/Objective: Brachytherapy is the cornerstone of radiotherapy treatment in cervical cancer. In the last decade an increasing number of publications based on single institution large series indicate MR based IGABT as the new gold standard of treatment allowing a dramatic decrease of morbidity and at the same time an increase in local control especially for large tumors. Hereby we describe preliminary dosimetric results of MR IGABT at our institution. Materials and Methods: Since December
more » ... 12, 71 consecutive patients (median age 50,5; range 31-88,5) with a histologically proven diagnosis of locally advanced cervical cancer have been referred to GYN tumor board at our Institution. FIGO stage distribution was the following: 5 had Ib1, 4 had Ib2, 1 had IIA, 28 had IIB with mid proximal parametrial invasion, 12 had IIB with distal parametrial invasion, 1 had IIIA, 13 had IIIB (11 because pelvic wall invasion), 7 had IVA cancers. All cases were Diagnostic routine for all patients consisted in thorax and abdomen CT and pelvic MR. PET CT was obtained in selected cases. All patients had laparoscopic retroperitoneal lymphadenectomy. All patients received radio-chemotherapy consisting 3DCRT (45 Gy in 25 fr.) concomitant to chemotherapy (weekly cisplatin 40 mg m2) followed by 4 fraction of 7 Gy each within two different BT insertions. Median overall treatment time was 43 days. 2-3 days before 1 BT implant all patients had a T2 MR scan to define tumor regression during radio-chemotherapy. All BT applications were performed under spinal anesthesia with TRUS and trans-abdominal US guidance. We used MR compatible Tandem Ovoids applicators (Elekta Utercht type) or Tandem Ring applicator (Elekta Vienna type) with either plastic or titanium needles if needed. At first application all patients had an MR with the applicator in place and a i.v. contrasted CT. A direct reconstruction approach based on applicator library or template was used to reconstruct applicators on MR images. Target volumes and OAR were contoured on MR according GEC ESTRO reccomendations. In all cases we started the planning process with a standard point A plan which was subsequently modified in order to reach our planning aims that are the following: HRCTV D9086Gy EQD2, Bladder D2cc<90 Gy EQD2, Rectum and Sigmoid bowel D2cc<70 GyEQD2. In the present study we report DVH comparison between Standard and optimized plans. Results: Preliminary dosimetric results are summarized in fig. 1 . At the present moment we had 2 patients with persistent disease after BT. Both cases were large IIIB tumors with infiltrative growth pattern and received a D90 dose of 85,21 and 85,51 Gy EQD2 respectively. No intraoperative or perioperative events have been registered so far. Conclusions: In our preliminary experience MR based IGABT is strikingly superior to standard treatment. Purpose/Objective: Image-Guided brachytherapy (IGBT) is related to treatment based on the 3D imaging for the planning procedure, not for the evaluation of the precision and accuracy of the treatment, which is the goal of the Image-Guided radiotherapy (IGRT). The aim of this study was assessment of probable intra-fractional organ displacement after the 3D imaging of the planning purpose. Materials and Methods: Thirty intracavitary bracytherapy insertions (with Rotterdam's tandem and ovoid applicators) of cervical cancer patients were studied. A CT scanning were done for each of the cases, for treatment planning, after the applicator insertion. Treatment planning was based on getting 80-90 Gy total dose to D90 of the HR-CTV (EQD2) and 70Gy and 80Gy for rectum and bladder (D2cc), respectively. For each of those insertions a second CT scan were performed for the patients, just after the finishing of her treatment and before the applicators removed from her body. The scanning protocols (e.g. the amount of normal saline injection to the bladder Foley) were the same as the first CT imaging. Organ contouring and applicators reconstructions were performed with the same physician and physicist. The first 3D treatment planning were copied
doi:10.1016/s0167-8140(15)41021-7 fatcat:qfwmigtn2ncdzknjyib57jkzwi