Treatment planning for carcinoma of the cervix: a patterns of care study report

The Patterns of Care Study (PCS) of patients treated in 1988-89 included "patterns of treatment planning" for radiotherapy of carcinoma of the uterine cervix. A Consensus Committee of radiation physicists and oncologists established current guidelines and developed questionnaires to assess the treatment planning process (i.e., the general structure, methodology, and tools) of institutions involved in the Patterns of Care Study. This paper reports the findings of the assessment.

The PCS surveyed 73 radiotherapy facilities, of which 21 are academic institutions (AC), 26 hospital-based facilities (HB), and 26 free-standing centers (FS). In total, 242 cases were assessed with 39% from academic centers, 33% from hospital-based centers, and 28% from free-standing centers. The survey collected treatment planning information such as the use of computed tomography (CT), simulation procedure, contouring of patient outline, tumor or target delineation, identification of critical structures, method of dose prescription (point or isodose), etc. Data was also obtained concerning implant boosts, e.g., radioisotope used, use of midline block for external beam treatment, availability of remote afterloader, practice of interstitial implants, combination with hyperthermia, etc.

There is a high degree of compliance relative to the basic treatment planning standards. For example, 171 cases (out of 173) from AC and HB institutions included simulation and 169 used port film; for cases from FS centers, 61 out of 69 involved simulation and 66 out of 69 included port film. Most institutions used linacs (231 out of 242); in five cases, Co-60 units and in six cases betatron was used. In terms of treatment planning, 53% used skin contours, but only 14% had target volume delineation, with AC and HB being slightly more conscientious in these efforts. Critical organs did not appear to be explicitly considered in external beam treatment planning, with only 3% outlining the bladder, 5% the rectum, and less than 1% the small bowel. Only 11% of the centers used CT in treatment planning, and none reported the use of magnetic resonance imaging (MRI). For patients receiving implants, about 40% had midline blocking during external beam treatment, of which one out of three were shielded by standard blocks and two out of three with customized ones. About 11% of the patients receiving implants were treated with remote afterloading devices, 5% received interstitial implants, and none were treated in combination with hyperthermia.

The treatment planning aspects of radiotherapy of carcinoma of the cervix have been established by this Patterns of Care Study Survey. There is a high level of uniformity in the approach. Some variations exist among centers in the different strata.