A technique for accurate planning of stereotactic brain implants prior to head ring fixation.

PURPOSE: A two-step procedure is described for accurate planning of stereotactic brain implants prior to head-ring fixation. METHODS AND MATERIALS: Approximately 2 weeks prior to implant a CT scan without the head ring is performed for treatment-planning purposes. An entry point and a reference point, both marked with barium and later tattooed, facilitate planning and permit correlation of the images with a later CT scan. A plan is generated using a conventional treatment-planning system to determine the number and activity of I-125 seeds required and the position of each catheter. I-125 seed anisotropy is taken into account by means of a modification to the treatment planning program. On the day of the implant a second CT scan is performed with the head ring affixed to the skull and with the same points marked as in the previous scan. The planned catheter coordinates are then mapped into the coordinate system of the second CT scan by means of a manual translational correction and a computer-calculated rotational correction derived from the reference point coordinates in the two scans. RESULTS: The rotational correction algorithm was verified experimentally in a Rando phantom before it was used clinically. For analysis of the results with individual patients a third CT scan is performed 1 day following the implant and is used for calculating the final dosimetry. CONCLUSION: The technique that is described has two important advantages: 1) the number and activity of seeds required can be accurately determined in advance; and 2) sufficient time is allowed to derive the best possible plan.

Increased risk of second malignant neoplasms outside radiation fields in patients with cervical carcinoma.

BACKGROUND: The relative risk of second primary cancers was evaluated in 125 women with International Federation of Gynecology and Obstetrics (FIGO) Stages I and II cervical carcinoma treated radically with radiation therapy between January 1980 and December 1990. METHODS: Medical records of patients were reviewed to evaluate the incidence of second malignant neoplasms. Only tumors histologically proven were scored. The annual 5-year age-specific cancer incidence data per 100,000 white women in the years 1981-1985 were obtained from the National Cancer Institute's Surveillance, Epidemiology and End Results database. The relative risks were calculated as the ratio of observed-to-expected numbers of second cancers, using person-years at risk accumulated for each individual in the study. RESULTS: During the follow-up time (through December 1992), 10 women whose median age was 65.5 years at the time cervical cancer was diagnosed were found to have 11 second primary cancers. Nine of these cancers were metachronous with regard to cervical cancer and included breast (4), lung (2), myeloma (1), non-Hodgkin's lymphoma (1) and vulva(1). The metachronous tumors were diagnosed at a median age of 74 years and at median follow-up time of 34 months. Two of the cancers were synchronous with cervical cancer and included bladder (1) and thyroid (1). All of the second tumors were located outside radiation fields. None of the patients with second tumors received chemotherapy during treatment for cervical carcinoma. The relative risk of developing a second cancer of any type was 2.31 (95% confidence interval [CI] = 1.15-4.13), whereas the relative risk of developing a metachronous breast cancer was 2.64 (95% CI = 0.72-6.75). CONCLUSIONS: An increased risk of second primary cancers developing was observed among 125 patients with FIGO Stages I and II cervical carcinoma, which may suggest an abnormal genetic background and/or a common etiology for the initial and second tumors. The increased risk of breast cancer occurring as a second primary is in contrast with previously published studies reporting a decreased risk of breast cancer in survivors of cervical cancer.