Comparison of kilovoltage x-ray and electron beam dose distributions for radiotherapy of the sternum.

The dose distributions for a patient with cancer involving the sternum were calculated for both a kilovoltage x-ray beam and a megavoltage electron beam. The minimum target dose and dose uniformity over the target volume were significantly better using electrons (90%-101%) than kilovoltage x-rays (68%-119%). The calculated lung dose and integral patient dose were also less for electrons than kilovoltage x-rays. For treating cancers of the sternum with radical intent, megavoltage electrons are recommended as the treatment mode of choice rather than kilovoltage x-rays.