title: Biodistribution of a carborane-containing porphyrin as a targeting agent for Boron Neutron Capture Therapy of oral cancer in the hamster cheek pouch.
abstract: Boron Neutron Capture Therapy (BNCT) is a bimodal cancer treatment based on the selective accumulation of 10B in tumors and concurrent irradiation with thermalized neutrons. The short-range, high-LET radiation produced by the capture of neutrons by 10B could potentially control tumor while sparing normal tissue if the boron compound targets tumor selectively within the treatment volume. In previous studies, we proposed and validated the hamster cheek pouch model of oral cancer for BNCT studies, proved that absolute and relative uptake of the clinically employed boron compound boronophenylalanine (BPA) would be potentially therapeutic in this model and provided evidence of the efficacy of in vivo BPA-mediated BNCT to control hamster oral mucosa tumors with virtually no damage to normal tissue. We herein present the biodistribution and pharmacokinetics of a lipophilic, carborane-containing tetraphenylporphyrin (CuTCPH) in the hamster oral cancer model. CuTCPH is a novel, non-toxic compound that may be advantageous in terms of selective and absolute delivery of boron to tumor tissues. For potentially effective BNCT, tumor boron concentrations from a new agent should be greater than 30 ppm and tumor/blood and tumor/normal tissue boron concentration ratios should be greater than 5/1 without causing significant toxicity. We administered CuTCPH intraperitoneally (i.p.) as a single dose of 32 microg/g body weight (b.w.) (10 microg B/g b.w.) or as four doses of 32 microg/g b.w. over 2 days. Blood (Bl) and tissues were sampled at 3, 6, 12, 24, 48, and 72 h in the single-dose protocol and at 1-4 days after the last injection in the multidose protocol. The tissues sampled were tumor (T), precancerous tissue surrounding tumor, normal pouch (N), skin, tongue, cheek and palate mucosa, liver, spleen, parotid gland and brain. The maximum mean B ratios for the single-dose protocol were T/N: 9.2/1 (12h) and T/Bl: 18.1/1 (72 h). The B value peaked to 20.7+/-18.5 ppm in tumor at 24h. The multidose protocol maximum mean ratios were T/N: 11.9/1 (3 days) and T/Bl: 235/1 (4 days). Absolute boron concentration in tumor reached a maximum value of 116 ppm and a mean value of 71.5+/-48.3 ppm at 3 days. The fact that absolute and relative B values markedly exceeded the BNCT therapeutic threshold with no apparent toxicity may confer on this compound a therapeutic advantage. CuTCPH-mediated BNCT would be potentially useful for the treatment of oral cancer in an experimental model.
authors.affiliation: Department of Radiobiology, National Atomic Energy Commission, Avenida del Libertador 8250, Buenos Aires 1429, Argentina.
authors.forename: Erica L
authors.initials: EL
authors.lastname: Kreimann
authors.forename: Michiko
authors.initials: M
authors.lastname: Miura
authors.forename: María E
authors.initials: ME
authors.lastname: Itoiz
authors.forename: Elisa
authors.initials: E
authors.lastname: Heber
authors.forename: Ricardo N
authors.initials: RN
authors.lastname: Garavaglia
authors.forename: Daniel
authors.initials: D
authors.lastname: Batistoni
authors.forename: Raúl Jiménez
authors.initials: RJ
authors.lastname: Rebagliati
authors.forename: Mariía J
authors.initials: MJ
authors.lastname: Roberti
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Micca
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Coderre
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Schwint
mesh_terms: D000818:Animals; D001895:Boron / Q000493:pharmacokinetics; D016754:Boron Neutron Capture Therapy / Q000379:methods*; D002610:Cheek; D006224:Cricetinae; D004195:Disease Models, Animal; D008647:Mesocricetus; D009061:Mouth Mucosa / Q000378:metabolism; D009062:Mouth Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D011166:Porphyrins / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D011166:Porphyrins; C409084:tetraphenylporphyrin; D001895:Boron