Over 20 years of progress in radiation oncology: Cervical cancer

Carcinoma of the cervix remains of special interest to the Patterns of Care Study (PCS) because of the prominent role that radiotherapy plays in the definitive management of all stages and extents of disease. Five PCS surveys have been conducted for squamous cell cancer of the uterine cervix beginning in 1973 and repeated thereafter at 5-year intervals. The records of over 2,700 women have been reviewed for these surveys. Changes in the pretreatment investigations of cervical cancer patients have occurred during these years, with an increase in the use of computed tomography (CT) and a decrease in the use of intravenous pyelography and cystoscopy. A marked increase in the use of linear accelerators has also occurred, with 98% of all facilities having a linear accelerator as the highest energy treatment machine in the 1988 survey. There has been a change in brachytherapy prescription over the time of the surveys, with most institutions reporting point dose calculations and dose distributions instead of milligram hours. Mean point A dose has increased to approximately 80 cGy, reflecting the PCS recommendations of dose intensity to the paracentral point through use of brachytherapy. The outcome for stage I and II cervical cancer has remained stable over the time of the surveys, while the results have improved for stage III disease. This improvement in survival and local control for stage III cervical cancer corresponds to an increased use of brachytherapy. The change in outcome for stage III cervical cancer is due in part to the PCS, which has developed standards of treatment with the goal of radiation dose intensity. A number of patient, tumor, and treatment factors significant in multivariate analysis have been described by the PCS with large cohorts of patients. The most important treatment factors associated with a decrease in pelvic failure and improved survival are the use of brachytherapy and higher paracentral dose. A significant dose response has been described for stage III cervical cancer and optimal pelvic control has been demonstrated with point A doses above 8,500 cGy. Other treatment factors associated with improved outcome include the reduction of overall treatment time, particularly for stage III cervical cancer, and the adequacy of an intracavitary placement. The rate and time course of major complications associated with radiation for cervix cancer has been described by the PCS. An increase in complications was seen for young patients and those with a history of abdominal surgery. Treatment factors that increased the risk of complications included a fraction size greater than 200 cGy, a paracentral dose greater than 7,500 cGy, and the use of staging laparotomy via a transperitoneal approach. Through the findings of the PCS, national averages of the process and outcome of radiation for cervical cancer as well as the important patient, tumor, and treatment factors that affect outcome have been reported. These results have positively affected routine clinical practice. Greater emphasis is placed on the use of intracavitary radiation therapy (RT) and dose escalation, as well as on a reduction in overall treatment time for cervical cancer. Future research will focus on the use of new technologies, such as high-dose rate brachytherapy and the impact of CT- and magnetic resonance imaging-directed treatment planning on local tumor control and survival. It will specifically evaluate the radiation treatment and outcome of minority populations. It will also measure the adoption of the results of positive clinical trials and the findings from previous PCS analyses into the national practice of radiation oncology.