title: Magnetic resonance imaging of temperature-sensitive liposome release: drug dose painting and antitumor effects.
abstract: BACKGROUND
  In preclinical studies, lysolipid-based temperature-sensitive liposomes (LTSLs) containing chemotherapy drugs administered in combination with local hyperthermia have been found to increase tumor drug concentrations and improve antitumor efficacy of the drugs. We used a novel magnetic resonance imaging (MRI) method to measure the temporal and spatial patterns of drug delivery in a rat fibrosarcoma model during treatment with LTSLs containing doxorubicin and an MRI contrast agent (manganese) (Dox/Mn-LTSLs) administered at different times with respect to hyperthermia.
  
  
  METHODS
  Rats bearing 10- to 12-mm fibrosarcomas (n = 6-7 per group) were treated with Dox/Mn-LTSLs (at a dose of 5 mg doxorubicin/kg body weight) before and/or during 60 minutes of local tumor hyperthermia administered via a catheter inserted at the center of the tumor. Drug distribution was monitored continuously via MRI. Magnetic resonance changes were used to calculate intratumoral doxorubicin concentrations throughout treatment. Tumors were monitored until they reached five times their volume on the day of treatment or 60 days. Doxorubicin concentrations and times for tumors to reach five times their volume on the day of treatment were analyzed using the Kruskal-Wallis test and the Kaplan-Meier product-limit method, respectively. All statistical tests were two-sided.
  
  
  RESULTS
  Administration of Dox/Mn-LTSLs before, during, and both before and during hyperthermia yielded central, peripheral, and uniform drug distributions, respectively. Doxorubicin accumulated more quickly and reached higher concentrations in the tumor when Dox/Mn-LTSLs were administered during hyperthermia than when administered before hyperthermia (rate: 9.8 versus 1.8 microg/min, difference = 8.0 microg/min, 95% confidence interval [CI] = 6.8 to 12.8 microg/min, P = .003; concentration: 15.1 versus 8.0 ng/mg, difference = 7.1 ng/mg, 95% CI = 3.6 to 10.6 ng/mg, P = .028). LTSL administered during hyperthermia also yielded the greatest antitumor effect, with a median time for tumors to reach five times their volume on the day of treatment of 34 days (95% CI = 30 days to infinity) compared with 18.5 days (95% CI = 16 to 23 days) for LTSL before hyperthermia and 22.5 days (95% CI = 15 to 25 days) for LTSL before and during hyperthermia.
  
  
  CONCLUSIONS
  In this rat fibrosarcoma model, LTSLs were most effective when delivered during hyperthermia, which resulted in a peripheral drug distribution.
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC, USA.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Ponce
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Viglianti
authors.forename: Daohai
authors.initials: D
authors.lastname: Yu
authors.forename: Pavel S
authors.initials: PS
authors.lastname: Yarmolenko
authors.forename: Charles R
authors.initials: CR
authors.lastname: Michelich
authors.forename: Janet
authors.initials: J
authors.lastname: Woo
authors.forename: Marcel B
authors.initials: MB
authors.lastname: Bally
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dewhirst
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D003287:Contrast Media / Q000008:administration & dosage; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D005260:Female; D005354:Fibrosarcoma / Q000188:drug therapy* / Q000378:metabolism; D006979:Hyperthermia, Induced; D008081:Liposomes; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017895:Manganese Compounds / Q000008:administration & dosage; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
chemical_list: D000903:Antibiotics, Antineoplastic; D003287:Contrast Media; D008081:Liposomes; D017895:Manganese Compounds; D004317:Doxorubicin