Radiotherapy after breast-conserving surgery increases local control. We tested the feasibility of limited surgery with tumor bed irradiation only with 192Ir in a selected group of patients with stage I breast cancer. Twenty-five breasts in 24 women more than 60 years old with low- or intermediate-grade stage I tumors were treated with placement of interstitial catheters at the time of lumpectomy and axillary node dissection. This procedure was followed by after-loading with low-dose 192Ir to deliver 20-25 Gy to the tumor bed over 24-48 hours. There were neither local recurrences in the breast nor distant recurrences at a median follow-up of 47 months (range 25-90 months). Cosmetic appearance ranged from very good to excellent. There were no long-term complications. It is feasible to treat a select group of patients with tumor bed irradiation, using relatively low doses of interstitial irradiation, with excellent local control and no significant morbidity.
In the previous paper we had developed a general thermodynamic equation describing a polymethylmethacrylate implant at the site of giant cell tumors. In this paper we consider various characteristics of bone and methylmethacrylate crucial to the analysis such as thermal conductivity, specific heat, density, and heat generation. Also, an estimation of the temperature at which adjacent cells die is analyzed from literature. Finally, using the physical constants measured in laboratory situations a temperature profile is developed at various depths of bone that could facilitate predicting the zone of necrosis. These analyses show the maximum temperature attained in the acrylic cement-bone system depends primarily on the volume of the implant, the relative proportion of polymerization of the monomer, the temperature at which the monomer and polymer are mixed together, and the time lapse between the beginning of polymerization and implantation into the bone cavity. The temperature profile is shown to be relatively insensitive to the geometry of the system, greatly simplifying the analysis.
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