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To prepare long-circulating liposomes, poly(ethylene glycol) (PEG)-lipid is usually mixed with other lipid components before vesicle formation. PEG-lipids can also be postinserted in the outer layer of liposomes after the preparation. In this study, PEG-distearoylphosphatidylethanolamine was incorporated by postinsertion technique into liposome-encapsulated hemoglobin (LEH) carrying neutral or negative charge. Postinsertion technique improved the encapsulation efficiency of hemoglobin from about 0.0017 to 0.017 (hemoglobin/phospholipid, molar ratio) for a similar lipid composition. Thus, neutral, anionic, PEG-neutral, and PEG-anionic LEHs were made and labeled with technetium-99m to follow their biodistribution. A small dose of LEH (ϳ15 mg of phospholipid) was injected intravenously in rabbits, and its distribution was monitored by blood sampling, gamma camera imaging, and tissue radioactivity counting on necropsy. The 24-h blood levels of neutral, PEGneutral, anionic, and PEG-anionic LEHs were 14, 40.3, 13.1, and 35.7% of injected dose, respectively; calculated T 1/2 values of circulation were 8.9, 19.3, 9.6, and 16.5 h, respectively. PEGylation also influenced accumulation of LEH in the reticuloendothelial system. Liver uptake of neutral LEH dropped from 52.1 to 19.1%, whereas that of anionic LEH came down from 35.3 to 11.5% on PEGylation. In contrast, PEGylation increased the spleen uptake by 8.5-and 2.5-fold for neutral and anionic LEH, respectively. The results demonstrate that PEGylation by postinsertion not only improves the circulation t 1/2 of LEH but also enhances hemoglobin content inside the vesicles for better oxygen-carrying capacity.

BACKGROUND. This report presents 3 years of data on treatment efficacy, cosmetic results, and toxicities for patients enrolled on the American Society of Breast Surgeons MammoSite (Cytyc, Bedford, Mass) Breast Brachytherapy Registry Trial. METHODS. A total of 1440 patients (1449 cases) with early stage breast cancer who were undergoing breast‐conserving therapy were treated with the MammoSite device to deliver accelerated partial breast irradiation (APBI) (34 Gy in 3.4 Gy fractions). Of these, 1255 (87%) cases had invasive breast cancer (IBC; median size = 10 mm), and 194 (13%) cases had ductal carcinoma in situ (DCIS; median size = 8 mm). Median follow‐up was 30.1 months. RESULTS. Twenty‐three (1.6%) cases developed an ipsilateral breast tumor recurrence (IBTR) for a 2‐year actuarial rate of 1.04% (1.11% for IBC and 0.59% for DCIS). No variables were associated with IBTR. Six (0.4%) patients developed an axillary failure. The percentages of breasts with good to excellent cosmetic results at 12 (n = 980), 24 (n = 752), 36 (n = 403), and 48 months (n = 67 cases) were 95%, 94%, 93%, and 93%, respectively. Breast seromas were reported in 23.9% of cases (30% in open‐cavity implants and 19% in closed‐cavity implants). Symptomatic seromas occurred in 10.6% of cases, and 1.5% of cases developed fat necrosis. A subset analysis of the first 400 consecutive cases enrolled was performed (352 with IBC, 48 DCIS). With a median follow‐up of 37.5 months, the 3‐year actuarial rate of IBTR was 1.79%. CONCLUSIONS. Treatment efficacy, cosmesis, and toxicity 3 years after treatment with APBI using the MammoSite device are good and similar to those reported with other forms of APBI with similar follow‐up. Cancer 2008. © 2008 American Cancer Society.

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