We suspect there are fundamental differences in the amount of exposure to radiation a patient has using these techniques, but no one has ever looked at how much normal tissue is spared, she says. We are interested in the finer points of treatment planning, with the ultimate goal of making treatment more tolerable with less radiation exposure.
In the first study, the researchers analyzed radiation plans for 25 patients enrolled in the clinical trial and they calculated what radiation to the lung would be if WBI or PBI was used. They found that PBI exposes a slightly larger volume of the lung to low doses of radiation, but also exposes a smaller volume of lung to high doses than WBI does.
Patients are getting more exposure overall to their lungs with partial breast irradiation but less lung tissue is irradiated to higher doses compared to whole breast irradiation, Vallow says.
For 14 of the same patients who had a lumpectomy in their left breast, investigators calculated radiation to normal heart tissue. They found that PBI and WBI delivered about the same amount of radiation to the heart of patients whose tumor was located in the middle of the breast. In patients whose tumors were closer to the armpit, PBI did not affect normal heart tissue, Vallow says.
This study shows how far we have really come in the delivery of radiotherapy, she says. We are looking for nuances of tissue exposure.
|Contact: Kevin Punsky|