Tumor control probability in head and neck fractionated radiation therapy: isoeffect parameters study

• Grant number: 17/14162-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2017
• End date: September 30, 2018
• Field of knowledge: Health Sciences - Medicine - Medical Radiology
• Principal Investigator: Patrícia Nicolucci
• Grantee: Miriã dos Santos Godói
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Dose fracionation in radiation therapy is usually used to spare normal tissues surrounding the tumor. Convencional fractionation, used in most cases, assumes a daily dose fraction, with total treatment time of, in average, 30 to 40 days. Nowadays, the technologycal development has allowed the test of different fractionation protocols in the treatment of tumors with diverse characteristics and differet locations. The comparison and choice between two fractionation protocols is made using isoeffect parameters, such as the Biologically Effective Dose (BED) and the Equivalent Dose (EQD), both based on linear-quadratic model (LQ) of biological effects from ionizing radiation. However, the classical LQ model doesn t offer a good estimation of damage for high replicating tumors or for incomplete repair between fractions, as found in hyperfracionation of head and neck trataments. In this work, the isoeffect of differnt fractionation protocols in head and neck radiation therapy will be studied using a numerical approach and considering different radiobiological models and isoeffect parameters. Accelerated and hyperfracionated protocols for these tumors and for normal tissues will be studied. In all the cases, the conventional fractionation will be used as reference. The isoeffect parameters will be compared to the Tumor Control Probability (TCP) to evaluate is effectivity in comparing fractionation protocols. (AU)