The determination of radiobiologically optimized half-lives for radionuclides used in permanent brachytherapy implants

Armpilia, CI; Dale, RG; Coles, IP; Jones, B; Antipas, V

dc.contributor.author	Armpilia, CI	en
dc.contributor.author	Dale, RG	en
dc.contributor.author	Coles, IP	en
dc.contributor.author	Jones, B	en
dc.contributor.author	Antipas, V	en
dc.date.accessioned	2014-03-01T01:19:36Z
dc.date.available	2014-03-01T01:19:36Z
dc.date.issued	2003	en
dc.identifier.issn	0360-3016	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/15598
dc.subject	Linear-quadratic	en
dc.subject	Permanent implants	en
dc.subject	Radiobiologic modeling	en
dc.subject	Therapy radionuclides	en
dc.subject.classification	Oncology	en
dc.subject.classification	Radiology, Nuclear Medicine & Medical Imaging	en
dc.subject.other	Growth kinetics	en
dc.subject.other	Implants (surgical)	en
dc.subject.other	Tissue	en
dc.subject.other	Tumors	en
dc.subject.other	Biologically effective dose	en
dc.subject.other	Radioisotopes	en
dc.subject.other	cesium 131	en
dc.subject.other	gold 198	en
dc.subject.other	iodine 125	en
dc.subject.other	palladium 103	en
dc.subject.other	radioisotope	en
dc.subject.other	unclassified drug	en
dc.subject.other	ytterbium 169	en
dc.subject.other	article	en
dc.subject.other	dose calculation	en
dc.subject.other	drug delivery system	en
dc.subject.other	drug half life	en
dc.subject.other	nonhuman	en
dc.subject.other	priority journal	en
dc.subject.other	prostate adenocarcinoma	en
dc.subject.other	prostate tumor	en
dc.subject.other	radiation dose	en
dc.subject.other	radiation dose fractionation	en
dc.subject.other	radioisotope therapy	en
dc.subject.other	tumor growth	en
dc.subject.other	Brachytherapy	en
dc.subject.other	Cell Division	en
dc.subject.other	Half-Life	en
dc.subject.other	Humans	en
dc.subject.other	Linear Models	en
dc.subject.other	Neoplasms	en
dc.subject.other	Radiation Tolerance	en
dc.subject.other	Radiobiology	en
dc.subject.other	Radioisotopes	en
dc.subject.other	Relative Biological Effectiveness	en
dc.title	The determination of radiobiologically optimized half-lives for radionuclides used in permanent brachytherapy implants	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/S0360-3016(02)04208-6	en
heal.identifier.secondary	http://dx.doi.org/10.1016/S0360-3016(02)04208-6	en
heal.language	English	en
heal.publicationDate	2003	en
heal.abstract	Purpose: To use tumor growth kinetics and other biologic parameters in an extended version of the linear-quadratic (LQ) formulation to determine radiobiologically optimized half-lives of radionuclides which might be used in permanent brachytherapy implants. Methods and Materials: A version of the LQ model suitable for the analysis of permanent brachytherapy implants has been modified to investigate the radionuclide half-lives that will maximize the biologically effective dose (BED) delivered to tumors with repopulation rates (K values) in the range 0.01-1.1 Gyday(-1). The method assumes that part of the physical dose delivered to the tumor may be radiobiologically wasted because of the repopulation phenomenon, whereas adjacent normal tissues will exhibit little or no wastage. To perform the analysis, it is necessary to stipulate alpha/beta ratios and sublethal damage recovery rates together with the normal tissue tolerance BED. The analysis also takes into account a range of likely relative biological effectiveness (RBE) values. Results: Rapidly growing tumors require the shortest radionuclide half-lives, but even slow-growing tumors such as prostate adenocarcinomas can be satisfactorily treated with radionuclides possessing half-lives substantially less than that associated with I-125. The likelihood that prostate tumors possess an alpha/beta value which is comparable with, or lower than, that associated with late-responding normal tissues would also mitigate against the use of long-lived radionuclides. Although a number of parameter assumptions are involved, the results suggest that, for a wide range of tumor types, shorter-lived radionuclides are more versatile for achieving reasonable clinical results. The theoretically derived optimum half-lives typically range from around 0-5 days for fast-repopulating tumors (K 1.1 Gyday(-1)) to approximately 14-50 days for slow-growing tumors (K similar to 0.1 Gyday(-1) or less). For prostate implantation, Pd-103 is overall a better choice than I-125. Conclusion: With so many variables and parameter uncertainties, it is not appropriate to attempt to define optimum radionuclide half-lives too closely. However, this study suggests that half-lives in the approximate range 4-17 days are likely to be significantly better for a wide range of tumor types for which the radiobiologic characteristics may not be precisely known in advance. (C) 2003 Elsevier Science Inc.	en
heal.publisher	ELSEVIER SCIENCE INC	en
heal.journalName	International Journal of Radiation Oncology Biology Physics	en
dc.identifier.doi	10.1016/S0360-3016(02)04208-6	en
dc.identifier.isi	ISI:000181323400012	en
dc.identifier.volume	55	en
dc.identifier.issue	2	en
dc.identifier.spage	378	en
dc.identifier.epage	385	en