Analysis of temperature distributions of interstitial hyperthermia using a hot water system.

PURPOSE: Interstitial hyperthermia is being increasingly used as an adjunct to brachytherapy in the treatment of implantable tumors. Of the several interstitial hyperthermia systems available, perhaps the simplest to use are the circulating hot water systems. An analysis of the thermal distributions obtained during our initial experience with interstitial hyperthermia using steel needles and the KHS-9 hot water system was therefore undertaken. METHODS AND MATERIALS: Between September 1988 and June 1991, 23 patients were treated with interstitial Iridium-192 high dose-rate brachytherapy immediately followed by interstitial hot water hyperthermia. A total of 32 implants were performed in these patients, of whom 14 presented with primary anal carcinomas, six with recurrent gynecological tumors, and three with subcutaneous metastases from malignant melanoma. All but the patients with anal cancers had failed in previously irradiated sites. One or two heat treatments were delivered to each tumor with the goal to reach and maintain an intratumoral temperature 42.5 degrees C over a period of 40 min. Temperature measurements were carried out by mapping three-point thermocouple probes along the track of one or two needles parallel to the implanted needles. RESULTS: Minimum intratumoral temperatures exceeded 42.0 degrees C in 41%, 42.5 degrees C in 19%, 43.0 degrees C in 13%, and 44.0 degrees C in 3% of treatments. The average minimum, maximum, and mean intratumoral temperatures for all treatments were 41.7 degrees C, 43.5 degrees C, and 42.6 degrees C, respectively. CONCLUSION: The temperature profiles obtained in this series compare favorable to those reported in literature for radiofrequency local current field systems and suggest the hot water device may be an alternative heating method. It is relatively simple to use, does not require shielding of the treatment room, and can easily be adapted to currently used brachytherapy systems. Further patient accrual and longer follow-up will be needed to assess the clinical results in terms of tumor response and duration of response.

Bladder and rectal dose of gynecologic high-dose-rate implants: comparison of orthogonal radiographic measurements with in vivo and CT-assisted measurements.

Bladder and rectal doses were retrospectively reviewed in 281 patients who underwent implantation of 575 gynecologic iridium-192 high-dose-rate devices. Dose measurements obtained with orthogonal radiography, in vivo thermoluminescent dosimetry, and computed tomography (CT)-assisted planning were compared. Measurements of bladder dose derived from radiographs revealed a significant difference between bladder neck dose and bladder base dose (P less than .0001). In 17% of cases, the dose to the bladder base was at least double the dose to the bladder neck. The mean dose to the rectum calculated from radiographs was 85.9% (cervix) and 90.2% (vaginal vault) of the prescribed fraction dose. The correlation coefficient factor between doses determined with orthogonal radiographs and doses determined with in vivo measurements was .9694. The dose to the bladder neck and to four rectal points determined with corresponding CT images revealed a deviation of 4% and 7%, respectively. However, calculations at the rectal wall cephalic to the specified rectal points showed higher doses to the rectum, with a ratio of 1-1.6. CT-assisted calculations at the bladder base also revealed doses that were higher than those obtained with radiographs alone by a ratio of 1.4-2.2. CT-assisted dosimetry is the method of choice.

Radiation therapy in stage III ovarian cancer following surgery and chemotherapy: prognostic factors, patterns of relapse, and toxicity: a preliminary report.

Twenty patients with FIGO stage III epithelial ovarian cancer who had undergone maximum cytoreductive surgery (including pelvic and paraaortic lymph node dissection) and combination chemotherapy (4-10 cycles, median 6) were treated with irradiation to the abdomen and pelvis with 30 Gy followed by diaphragmatic/paraaortic and pelvis boost fields to 42 and 51.6 Gy, respectively. Second-look laparotomy was not performed. Seventeen of 20 patients completed the planned course of radiation. In 2 cases, failure to complete treatment was related to acute hematologic toxicity, and 1 patient refused further treatment. Five patients (29%) required treatment breaks ranging from 8 to 16 days (median, 12 days) due to pancytopenia. Actuarial overall survival and relapse-free survival at 3 years for the 17 patients who completed radiation was 69 and 47%, respectively, with follow-up ranging from 19 to 53 months (median: 24, mean: 27.6 months). Seven patients (41%) relapsed within the abdomen alone and 2 patients developed extraabdominal lymph node metastasis as their sole site of failure. The prognostic factors evaluated for correlation with relapse-free survival included histologic subtype, grade, amount of residual disease at the time of surgery, and nodal involvement; only residual tumor at surgery (none vs less than or equal to 2 cm or greater than 2 cm) was found to be statistically significant (P less than 0.01). Three-year overall survival correlated with amount of residual disease following the initial cytoreductive surgery. It was 100% for patients with no residual disease, 66.7% for less than or equal to 2 cm, and 26.7% for those with greater than 2 cm residual disease, respectively. Radiation treatment was well tolerated, with only one patient developing treatment-related bowel obstruction 7 months after radiation therapy. The results of this planned trimodality treatment approach compare favorably with those reported following surgery and chemotherapy, particularly in patients who have been maximally cytoreduced.

Intraoperative plus external beam irradiation in nonresectable lung cancer: assessment of local response and therapy-related side effects.

Since 1987, 24 patients with inoperable non-small-cell lung cancer (NSCLC), stage T1-3 N0-2 M0, have undergone lymph node dissection and intraoperative radiation therapy (IORT) to the primary with 10-20 Gy. Patient selection criteria were nonresectability based on severe cardiorespiratory impairment, no radiological evidence of distant metastases and a Karnofsky performance status of greater than 80. In 18 patients the IORT procedure was followed by an external beam radiation series (EBR) including the tumor with 46 Gy and the regional lymph nodes with 46/56 Gy. The tumor response was assessed by CAT-scan volumetry before the institution of IORT, 4 weeks later, before the onset of EBR, 8 weeks after the combined treatment course and on a 3 months basis thereafter. Prospectively, MRI of the thorax with/without Gadolinium-DTPA was performed to examine contrast enhancement and signal behavior of the tumor, in an attempt to differentiate residual disease compared to therapy-related collateral damage. So far, 18 patients have completed the combined treatment course with a median follow-up of 11 months (range 4.5 to 25 months). The overall local response rate (CR and PR) was 88.2%. In detail, 11 complete responses, 6 partial responses and one minimal response were observed. The overall and recurrence-free survival at 25 months was 49.6% and 83.3%, respectively.