[CANCER RESEARCH 63, 6327– 6333, October 1, 2003] Radiofrequency Thermal Ablation Sharply Increases Intratumoral Liposomal Doxorubicin Accumulation and Tumor Coagulation 1 Muneeb Ahmed, Wayne E. Monsky, Geoffrey Girnun, Anatoly Lukyanov, Giuseppe D’Ippolito, Jonathan B. Kruskal, Keith E. Stuart, Vladimir P. Torchilin, and S. Nahum Goldberg 2 Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215 [M. A., W. E. M., G. D., J. B. K., S. N. G.]; Department of Medical Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215 [K. E. S.]; Department of Pharmaceutical Sciences, Bouve College of Health Sciences, Northeastern University, Boston, Massachusetts 02115 [A. L., V. P. T.]; and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115 [G. G.] ABSTRACT Combining radiofrequency (RF) ablation with i.v. liposomal doxorubi- cin (Doxil) increases intratumoral doxorubicin accumulation and tumor destruction. The purpose of this study was to characterize and better define the specific parameters of such treatment in an animal tumor model. Four hundred R3230 mammary adenocarcinoma nodules were implanted in 250 Fischer rats. First, paired tumors received combined standardized RF (70°C  2°C, 5 min) followed 30 min later with i.v. Doxil (1 mg) or Doxil alone. Intratumoral doxorubicin uptake was evaluated using fluorospectrophotometry 2–120 h after therapy (n  110). The effects of varying i.v. Doxil doses (0.0625–7.0 mg; n  100) and the RF tip temperatures (45°C–90°C; n  190) on subsequent intratumoral doxoru- bicin uptake and induced tumor necrosis were evaluated. Intratumoral doxorubicin accumulation increased to a maximum at 72 h with greater uptake in the RF-ablated tumors compared with controls (P < 0.01). Greater dose-dependent intratumoral doxorubicin increases (to 37.3  7.7 g/g) were seen with combined RF/Doxil therapy (P < 0.01). RF ablation reduced the i.v. Doxil dose needed to achieve intratumoral doxorubicin uptake of 13 g/g from 7 to 2 mg. Increasing tip temperatures from 50°C to 90°C increased the ratio of doxorubicin in RF to nonablated tumors from 1.2  0.4 to 5.9  3.8 (P < 0.01). At all temperatures, greater tumor necrosis was identified for RF/Doxil-treated tumors compared with tu- mors treated with RF alone (P < 0.05). The threshold for inducing necrosis was 5°C lower for tumors receiving combined therapy (P < 0.01). RF tumor ablation sharply increases intratumoral Doxil accumulation over i.v. Doxil alone, enabling a reduction of systemic dose while obtaining higher intratumoral concentrations than otherwise achievable. Combined therapy also increases tumor destruction over either therapy alone. INTRODUCTION Whereas surgical resection has traditionally been the standard of care for the treatment of focal malignancies, recent improvements in imaging technologies have enabled the development of minimally invasive high-temperature thermal tumor ablation, a technique that uses imaging guidance for the accurate percutaneous placement of needle-like applicators (1). The primary mechanism of tumor destruc- tion for these methods is based upon subjecting the entire tumor volume to cytotoxic temperatures (50°C) for short durations (4 –12 min) to induce tumor coagulation and necrosis from energy sources such as RF 3 (2, 3), microwave (4, 5), ultrasound (6, 7), and laser (8 –11). Thermal ablation strategies for focal tumor destruction have been gaining increasing clinical attention and rapid adoption as min- imally invasive alternatives to surgical resection in the treatment of localized malignancies in a wide range of sites, including liver (12, 13), breast (14), kidney (15–17), lung (18), and bone (11, 19). Clinical studies using RF ablation for liver tumors report that local tumor control can be achieved in 80 –90% of cases where the tumors meas- ure 2.5 cm in diameter, with less satisfactory results (50 –75% success) for the treatment of larger (3.5 cm) tumors (8). Addition- ally, with further long-term follow-up of ablation therapy, there has been an increased incidence in detection of progressive local tumor growth for all tumor types and sizes, despite initial indications of adequate therapy (20 –22). This suggests that there are residual patches of viable tumor cells in a substantial but unknown number of cases, a result that falls far short of a goal of completely eradicating all tumor treated by RF ablation. Therefore, strategies that can in- crease the uniformity and completeness of tumor destruction are needed. Increasing tumor destruction by combining chemotherapy with high-temperature thermal ablation can potentially overcome many of the current limitations posed when performing RF ablation alone. Based upon well-documented antitumor effects of chemotherapy combined with lower-temperature hyperthermia (41.5°C– 45°C), sev- eral recent studies have begun to explore the potentiation of effects that can be achieved with a combination of chemotherapy and RF ablation (23–26). For example, in a rat breast adenocarcinoma model, Goldberg et al. (23) reported significant increases in coagulation necrosis over RF alone or doxorubicin alone when RF was combined with the intratumoral injection of free doxorubicin and noted even greater increases in tumor destruction using a liposomal doxorubicin preparation (Doxil) administered i.v. (24, 26). Subsequently, Monsky et al. (25) observed a 5-fold increase in intratumoral uptake of liposomal doxorubicin in tumors treated with RF compared with tumors that received the drug alone, with preferential liposome accu- mulation in the hyperemic zone surrounding the ablated area. These advances have already gained substantial clinical interest because preliminary results from a randomized study using combined RF/ liposomal doxorubicin therapy in patients with primary and secondary liver tumors demonstrated significant increases in tumor necrosis compared with RF ablation alone (26). Whereas earlier studies have demonstrated the complementary role of i.v. liposomal doxorubicin therapy administered in conjunction with RF ablation both in terms of increased intratumoral drug uptake and tumor coagulation, further work needs to be done to better define the parameters for this treatment paradigm. In this study, we have demonstrated an increased efficacy of the combined application of RF ablation and liposomal doxorubicin in a rat breast adenocarcinoma model and investigated some specific parameters of such treatment. Special attention was paid to elucidate the pharmacokinetic charac- teristics of intratumoral liposomal doxorubicin uptake over time after RF treatment and characterize the effect of increased focal heating and i.v. liposomal doxorubicin dose on both induced necrosis and intra- tumoral doxorubicin uptake within treated tumors. Received 11/21/02; revised 6/24/03; accepted 7/21/03. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by Grant RO1-CA87992-01A1 from the National Cancer Institute, NIH (Bethesda, MD) and by Bracco Research SpA (Milan, Italy). Accepted for presentation at AACR 2003. 2 To whom requests for reprints should be addressed, at Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215. Phone: (617) 754-2674; Fax: (617) 754-2545; E-mail: sgoldber@caregroup.harvard.edu. 3 The abbreviation used is: RF, radiofrequency. 6327 Research. on December 3, 2021. © 2003 American Association for Cancer cancerres.aacrjournals.org Downloaded from