Medicina nuclear y radioterapia

A Verification of Treatment Protocol in Fractionated Radiotherapy by Biological Dosimetry

Abstract

Idil ÖNER, Tuncay ORTA, Melek Özlem KOLUSAYIN, Süreyya GÜNEBAKAN, Asuman Kaynar Öztaş and Mustafa Ünsal

In radiation therapy of cancer, any possible mistakes that may occur in prescribed tumour dose calculation and/ or in treatment set up could also be checked by the biological dosimetry. In order to verify this, 20 patients having pelvic area tumours with no prescribed chemotherapy were selected. Their peripheral blood samples were collected before starting fractionated radiotherapy and at some definite time during treatment. Equivalent whole body doses (EWBD) were calculated from patient’s weights, irradiated volumes and total tumor doses given until the date of blood sample collection during treatment. Each patient’s EWBD was given in vitro to blood samples that were collected before starting radiotherapy. Radiation induced chromosome damage in lymphocytes were measured by micronucleus (MN) induction.

The relationship between the micronucleus frequencies (MN/BN) scored during therapy ( in vivo ) and the micronucleus frequencies scored after the application of in vitro EWBD was investigated. MN/BN rates scored following in vitro application of EWBD differed between 0.195 and 0.540, whereas MN/BN rates obtained during radiotherapy equivalent to EWBD differed between 0.213 and 0.625. It was shown that there was no significant difference (p=0.653) between the MN scores following in vitro applied EWBD and MN scores obtained in vivo . The existence of this correlation has confirmed the correct application of fractionated radiotherapy and treatment setup for the patients.