The potential for proton beam therapy in locally advanced carcinoma of the cervix

Advanced cervix cancer has a local failure rate of 40-45% when treated with a combination of external beam irradiation and intracavitary implants, and approximately 60-65% when treated by external beam irradiation alone. Because of the absorption characteristics of protons, there is the potential for improved dose distributions and delivery of greater total doses to cervical neoplasms. Using computer-modelled examples, this theoretical advantage has been tested and the results have been extrapolated to show a therapeutic advantage in local control and morbidity. The first example shows the use of protons and intracavitary implants in advanced cervix tumors. Larger tumor doses are possible with protons than with photons, while the dose-volume to normal structures is decreased. In the second example, external proton beam treatment alone also reveals significantly higher tumor doses and lower normal tissue doses, compared to photon irradiation. With new proton therapy facilities being designed and built in the United States and overseas, protocols are being designed to evaluate the therapeutic potential of proton therapy in locally advanced cervix cancer.