1: Int J Radiat Oncol Biol Phys. 2005 Nov 15;63(4):1245-51. 

Changes in the tumor microenvironment during low-dose-rate permanent seed
implantation iodine-125 brachytherapy.

Cron GO, Beghein N, Crokart N, Chavee E, Bernard S, Vynckier S, Scalliet P,
Gallez B.

Laboratory of Biomedical Magnetic Resonance, Universite Catholique de Louvain,
Brussels, Belgium.

PURPOSE: There is a lack of data regarding how the tumor microenvironment (e.g.,
perfusion and oxygen partial pressure [pO2]) changes in response to
low-dose-rate (LDR) brachytherapy. This may be why some clinical issues remain
unresolved, such as the appropriate use of adjuvant external beam radiation
therapy (EBRT). The purpose of this work was to obtain some basic preclinical
data on how the tumor microenvironment evolves in response to LDR brachytherapy.
METHODS AND MATERIALS: In an experimental mouse tumor, pO2 (measured by electron
paramagnetic resonance) and perfusion (measured by dynamic contrast-enhanced
magnetic resonance imaging) were monitored as a function of time (0-6 days) and
distance (0-2 mm and 2-4 mm) from an implanted 0.5 mCi iodine-125 brachytherapy
seed. RESULTS: For most of the experiments, including controls, tumors remained
hypoxic at all times. At distances of 2-4 mm from radioactive seeds (
approximately 1.5 Gy/day), however, there was an early, significant increase in
pO2 within 24 h. The pO2 in that region remained elevated through Day 3.
Additionally, the perfusion in that region was significantly higher than for
controls starting at Day 3. CONCLUSION: It may be advantageous to give adjuvant
EBRT shortly (approximately 1 to 2 days) after commencement of clinical LDR
brachytherapy, when the pO2 in the spatial regions between seeds should be
elevated. If chemotherapy is given adjuvantly, it may best be administered just
a little later (approximately 3 or 4 days) after the start of LDR brachytherapy,
when perfusion should be elevated.

PMID: 16253779 [PubMed - indexed for MEDLINE]