2D vs 3D Planning for High-Dose Rate (HDR) Gynecological Brachytherapy

Radiotherapy is part of a multidisciplinary strategy to fight cancer in all stages, using ionizing radiation to cause damage in tumor cells. After radical surgical treatment of gynecological tumors, pathological findings, such as extension of the myometrium invasion, histologic grade, and vascular- lymphatic invasion predict the risk of locoregional recurrence of disease and, consequently, the need for adjuvant treatment. There are two main methods of adjuvant therapy after hysterectomy for malignant neoplasm of the cervix or endometrium: external beam radiotherapy with or without booster dose of vaginal vault brachytherapy or brachytherapy alone. There are few data in the literature and clinical experience with brachytherapy dimensional (3D) for adjuvant treatment of vaginal vault .

Objective: To demonstrate the limitations of conventional dosimetry (2D) for the adjuvant brachytherapy treatment and assess whether tridimensional dosimetry relates more faithfully with the occurrence of adverse effect.

Methods: A prospective study in the Department of Radiation Oncology, Antonio Candido Camargo Cancer Center will be developed with an expected duration of 14 months and will include 60 patients. Dosimetric parameters of brachytherapy treatment of vaginal vault, able to influence the incidence of adverse effects will be evaluated. Computed tomography for planning of external beam radiotherapy and brachytherapy planning will be used, after placement of intra- vaginal applicator and urinary catheter. For planning brachytherapy two fast acquisition sequences, one with a urinary catheter not pulled and pulled another with the probe will be obtained. The prescription dose obey the standard indication of document of the International Commission on Radiation Units & Measurements (ICRU 38).

Inclusion criteria

• Malignant neoplasm of the cervix or endometrium;
• Tomography scan available in the planning system.

Exclusion criteria

• Patients did not undergo surgery as initial treatment;
• Patients without available tomography for planning;