Rio de Janeiro ~ IRPA ~ Brasil ~t> 2013 -_-~~- -_ 14 -19'Abril

IX CONGRESO REGIONAL IRPA DE SEGURIDAD RADIOLÓGICA Y NUCLEAR V CONGRESO IBEROAMERICANO DE SOCIEDADES DE PROTECClÓN RADIOLÓGICA 111 CONGRESO BRASILENO DE PROTECCIÓN RADIOLÓGICA

5.2 BETA CHRONIC IRRAOIATION AT LOW DOSE RATE INOUCE G2/M

ARREST ANO BYSTANOER EFFECf

Severino C. Michelin, Cristina Ga llegos and Diana Dubner

Radiopathology laboratory. Nuclear Regulatory Authority (ARN). Av. Del Libertador8250 - 1429 BNP Buenos Aires, Argenline [email protected]

ABSTRACf

In arder to increase effectiveness ofradiotherapy, especially brachytherapy and radioimmunotherapy (RIT) and reduce unwanted side-efTecls 00 normal tissues, dilTerent monocJonal antibodies radiolabeled with Pernitters are used. For examp\ 131 1, 9O y ,.nLu , 67CU, ISó Re, 2l3Bi, 211 At and alhers, has shown to cause inhibition af tumor growth in several experimental models and during lhe treatment of patients Melanoma has been historically considered as relatively radioresistant tumor. However, newer data have challenged this view-point and radiation therapy is now considered to a useful eomponent for lhe treatment of malignant melanoma. The objeetive ofthis work was to determine the survival fraetion ofa human melanoma eell line continuously irradiated with J2p with an initial very low dose rate of 15 mGylh until a final dose of2 Gy. To study the effect ofexponentially decreasing non uniform low dose-rale irradiation ofeell cultures in a reproducible form, developed a simple and economic device for externai beta irradiation with J2p. We could determine a nearly 40% of diminution in cell survival under these experimental conditions. ln order to detennine some 3spect of mechanism of cel lulnr denth, we could observe fi progressive arrest in the G2/M phase, aceompanied byan increase in the levei of apoptosis and the existence of bystander efTect. Similar frequeney of survival, for a similar final dose with a dose rale of30.000 mGylh of gamma radialion, was obtained. This gamma irradiation eonditions are used frequently in radiotherapy regimes. Our results indieate thal very low dose rale beta irradiation was as effective as high dose rate gamma irradiation in inducing cell death in MS melanoma eells. This observation would be of particular interesl for lhe optimization of radiotherapy and radioimmunotherapy (RJT) protocols, lowering the dose reeeived by normal tissue and contributing to radioprotection of patient, prevenling side effecls.