Regional chemotherapy has been proposed as a treatment modality in a number of cancer settings. In primary or metastatic lung cancer, administration of chemotherapy via inhalation could increase exposure of lung tumor to the drug, while minimizing systemic side effects. Several proof of concept studies in animal models of metastatic or primary lung cancer have demonstrated the safety, pharmacokinetic advantage, and antitumor effect of aerosol administration of several chemotherapeutic agents including doxorubicin, gemcitabine and liposome-encapsulated formulations of paclitaxel and 9-nitrocamptothecin (9-NC). Recent phase I studies have demonstrated the feasibility of aerosol delivery of doxorubicin and liposomal formulations of 9-NC and cisplatin in patients with primary and metastatic lung cancer with a limited pharmacokinetic profile consistent with the observed low systemic toxicity. Further studies integrating safety, pharmacokinetic, and efficacy considerations are required to determine whether there is a place for local administration of chemotherapy via inhalation in lung cancer.
Background: Gamma camera imaging is widely used to assess pulmonary aerosol deposition. Conventional planar imaging provides limited information on its regional distribution. In this study, single photon emission computed tomography (SPECT) was used to describe deposition in three dimensions (3D) and combined with X-ray computed tomography (CT) to relate this to lung anatomy. Its performance was compared to planar imaging. Methods: Ten SPECT/CT studies were performed on five healthy subjects following carefully controlled inhalation of radioaerosol from a nebulizer, using a variety of inhalation regimes. The 3D spatial distribution was assessed using a central-to-peripheral ratio (C/P) normalized to lung volume and for the right lung was compared to planar C/P analysis. The deposition by airway generation was calculated for each lung and the conducting airways deposition fraction compared to 24-h clearance. Results: The 3D normalized C/P ratio correlated more closely with 24-h clearance than the 2D ratio for the right lung [coefficient of variation (COV), 9% compared to 15% p < 0.05]. Analysis of regional distribution was possible for both lungs in 3D but not in 2D due to overlap of the stomach on the left lung. The mean conducting airways deposition fraction from SPECT for both lungs was not significantly different from 24-h clearance (COV 18%). Both spatial and generational measures of central deposition were significantly higher for the left than for the right lung. Conclusions: Combined SPECT/CT enabled improved analysis of aerosol deposition from gamma camera imaging compared to planar imaging. 3D radionuclide imaging combined with anatomical information from CT and computer analysis is a useful approach for applications requiring regional information on deposition.
We have characterized a gemcitabine aerosol suitable for intrathoracic airway deposition and demonstrated that jet nebulization does not alter the cytotoxic properties of the drug. In a primate model, we have developed a scintigraphic procedure for the monitoring of aerosol deposition, and we have demonstrated the safety of nine weekly aerosol administrations of gemcitabine.
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