Cobalt-60 radiation beam verification in nasopharyngeal carcinoma: a Kenya experience

Abstract

Background and purpose The primary aim of this study was to analyse the accuracy and reproducibility of radiation treatment to patients with nasopharyngeal carcinoma at the only tertiary teaching and referral hospital in Kenya. The secondary objective was to review literature on quality assurance procedures that would result to provision of quality radiation treatment to this group of patients. Materials and method During the period May 2011 to March 2012, 35 patients with head and neck cancer comprising of 27 patients with nasopharyngeal carcinoma, 7 with paranasal sinus carcinoma and 1 with lymphoma falling within the enrolment criteria were treated using Equinox cobalt-60 unit with the same beam arrangement and were studied prospectively. Radical radiotherapy was delivered using conventional 2D technique in a routine dose of 60-66Gy to the primary and 50Gy to lymph nodes with additional dose to residual neck nodes. During the period of their treatment, a lateral portal image was taken once weekly. Four film image pairs were obtained per patient with each patient positioned and immobilised in an individualised Orfit thermoplastic mask and a head and neck support. The 4 portal images were compared to a corresponding simulator film taken during simulation planning. Deviations from the varied bony landmarks were measured on the portal images and simulator image from the centre of the radiation beam.