Calculation of mean central dose in interstitial brachytherapy using Delaunay triangulation

In 1997 the ICRU published Report 58 "Dose and Volume Specification for Reporting Interstitial Therapy" with the objective of addressing the problem of absorbed dose specification for reporting contemporary interstitial therapy. One of the concepts proposed in that report is "mean central dose." The fundamental goal of the mean central dose (MCD) calculation is to obtain a single, readily reportable and intercomparable value which is representative of dose in regions of the implant "where the dose gradient approximates a plateau." Delaunay triangulation (DT) is a method used in computational geometry to partition the space enclosed by the convex hull of a set of distinct points P into a set of nonoverlapping cells. In the three-dimensional case, each point of P becomes a vertex of a tetrahedron and the result of the DT is a set of tetrahedra. All treatment planning for interstitial brachytherapy inherently requires that the location of the radioactive sources, or dwell positions in the case of HDR, be known or digitized. These source locations may be regarded as a set of points representing the implanted volume. Delaunay triangulation of the source locations creates a set of tetrahedra without manual intervention. The geometric centers of these tetrahedra define a new set of points which lie "in between" the radioactive sources and which are distributed uniformly over the volume of the implant. The arithmetic mean of the dose at these centers is a three dimensional analog of the two-dimensional triangulation and inspection methods proposed for calculating MCD in ICRU 58. We demonstrate that DT can be successfully incorporated into a computerized treatment planning system and used to calculate the MCD.

Unresectable primary and recurrent head and neck tumors: effect of hyperthermia and carboplatin--preliminary experience

PURPOSE

To perform a single-arm study to determine the effectiveness of and potential toxic reactions to local hyperthermia and systemic carboplatin (cis-diammine-1,1-cyclobutane dicarboxylate platinum II) for the treatment of advanced or recurrent squamous cell carcinomas of the head and neck.

MATERIALS AND METHODS

Eight patients with squamous cell carcinoma of the head and neck and stage IV disease (N2 or N3 neck adenopathy) or recurrent local-regional disease and who were previously and definitively treated were included in the study. Thermochemotherapy was administered every 4 weeks. Recorded end points were tumor response, duration of response, incidence of distant metastases, survival, cause of death, and toxic reactions.

RESULTS

One patient had a complete response to therapy, and two had a partial response. Five patients had no response or developed progressive disease during therapy. Six patients died after 4-13 months of progressive disease. Two long-term survivors received radiation therapy; one also underwent surgical resection for residual neck disease. Each thermochemotherapeutic session was well tolerated, with minimal discomfort. Toxic reactions included hypotension, vomiting, hyponatremia, anemia, thrombocytopenia, and infection at the site of administration. There were no life-threatening toxic reactions.

CONCLUSION

The combined use of hyperthermia and carboplatin shows potential in the management of unresectable head and neck tumors and is safe and well tolerated. Further studies on thermochemotherapy are warranted to assess its potential.

Does race influence survival for esophageal cancer patients treated on the radiation and chemotherapy arm of RTOG #85-01?

PURPOSE

In reported retrospective non-randomized trials of treatment of esophageal carcinoma, blacks have a lower survival from esophageal cancer than whites. None of these studies has accounted for the extent of disease, or the methods and quality of treatment. We reviewed the data that included only patients treated on the chemoradiation arm of the RTOG-8501 esophageal carcinoma trial to see if there were differences in overall survival between black and white patients receiving the same standard of care.

METHODS AND MATERIALS

One hundred-nineteen patients, 37 blacks and 82 whites were evaluated who met the criteria for receiving chemoradiation of 5000 cGy and four courses of Cisplatin (75 mg/m2) and Fluorouracil (1000 mg/m2 for 4 days).

RESULTS

Blacks had squamous histology only, with 86% of blacks having weight loss of 10 lbs. or more compared to 56% of whites (p = 0.001). In addition, blacks had larger tumors and more difficulty eating (p = 0.010). Overall, there was no difference in the Kaplan-Meier median survival estimate by race (p = 0.2757). Only when we limited the analysis to the "squamous histology" subgroup, stratified according to age >70 vs. <70 years (p = 0.0002), and nodal status (p = 0.0177) in a Cox regression model analysis, did race appear to be a significant factor (p = 0.0012). However, using the entire database, the age effect was found to be a "bimodal" effect, wherein the "youngest" (< age 60 years) and "oldest" patients (age > 70 years) did poorly. Because of the dramatic differences in the age and histology distributions between blacks and whites, this issue could not be resolved in the subset of squamous only who received chemoradiation.

CONCLUSIONS

The increasing incidence of adenocarcinoma among white patients without a corresponding increase of this histology in blacks reflects a difference in diet and or lifestyle compared to blacks that deserves additional study. When treated aggressively with chemoradiation, race did not appear to be a statistically significant factor for overall survival.

Outcome of care. Complications from radiation therapy treatment

This study was undertaken to examine radiation treatment complications. From September 1987 through December 1989, 29,380 patients were screened at their follow-up visits for possible radiation complications. Of these patients, 1,380 were singled out for further study. These 1,380 charts were examined by a radiation oncologist and physicist to determine if there was a radiation complication, the severity of the complication, and whether a calculation or setup error could account for the complications. Of the 1,380 patients studied, 178 (3% of new patients treated each year) were determined to have radiation complications. These complications were divided into four categories of severity and entered into our computerized tumor registry as follows: complication type R1, complete recovery from symptoms, n = 59; R2, injury requiring medications to control injury, n = 104; S1, surgical intervention for one organ, n = 12; and S2, surgical intervention for two organs, n = 3. We believe that a baseline complication rate of 5% is acceptable in radiation oncology practices. However, the examination and documentation of the outcome of care in the form of radiation complications can help improve patient care and keep the radiation oncologist abreast of treatment outcome trends in the department.

Iodine125 interstitial brachytherapy in the treatment of carcinoma of the lung

In a prospective study, 14 patients with primary non-oat cell lung carcinoma were treated with intraoperative Iodine125 (I125) implantation of the lung tumor via lateral thoracotomy or median sternotomy. Staging mediastinal node dissection was performed in each case. Patients were selected when wedge or segmental resections were not technically feasible, such that lobectomy or completion pneumonectomy would have been required or pulmonary function studies were poor. Doses ranged from 8,000 cGy at the periphery to 20,000 cGy at the center. With a minimum 12 month follow-up, mean and median survivals were 16.7 and 15.1 months, respectively. Local control was achieved in 10 of 14 patients (71%) with all local failures occurring in pathologic stage III patients. When separated according to tumor size, local control was obtained in six of seven tumors of less than 3 cm and four of five tumors of 3-5 cm. Both cases with masses greater than 5 cm failed locally. There was one operative mortality and two postoperative complications. All other patients were discharged within one week of surgery. There was no radiation pneumonitis. I125 lung brachytherapy is an excellent alternative treatment for T1 and T2 tumors when medical conditions preclude curative resection.

Malignant pleural mesothelioma: a survival study

Ninety-four patients with malignant pleural mesothelioma were treated at Southern California Permanente Medical Group Facilities between 1965 and 1988. This retrospective analysis of survival in these patients is compared according to surgical and/or supportive management. Group I patients received supportive care only, including pleurodesis as needed. This group included the majority of patients. Group II patients were managed largely with debulking procedures including decortication and pleurectomy. Group III patients received extrapleural pneumonectomy. This group included the two long-term survivors of the entire group. This study of survival points out the need for a cooperative protocol as well as the consistent use of proper modern preoperative staging in an attempt to select patients who benefit from extrapleural pneumonectomy.

Effective palliation for inoperable esophageal cancer using intensive intracavitary radiation

In a pilot study between May 1988 and May 1989, ten consecutive patients with advanced esophageal cancer were treated with a short intensive course of intraluminal curietherapy without external beam irradiation at the Kaiser Permanente-Los Angeles Medical Center. Nine of ten patients achieved effective palliation comparable to that of standard external beam teletherapy from other series. Most patients had already failed other palliative modalities including chemotherapy, laser debridement, dilation, and electrocautery. The duration of response was generally longer than with these techniques. All patients completed therapy, and tolerance was excellent. Intraluminal irradiation is an attractive, effectual therapeutic alternative, especially in patients with advanced local or distant disease unlikely to tolerate 5 to 7 weeks of external beam therapy.

Prognostic factors for recurrence and cosmesis in 393 patients after radiation therapy for early mammary carcinoma

Between 1978 and 1985, 393 of 2,765 (14%) patients with operable cancer of the breast (clinical stage T0-3N0-2M0) were irradiated after excisional biopsy and staging axillary dissection. Of 77 patients with microscopic axillary metastases, 68 received systemic adjuvant therapy. Treatment failed locally in 26 cases, and there were seven patients with distant metastasis. The three major factors for increased local treatment failure were (a) age below 40 years (P = .003), (b) negative estrogen receptor assay result (P = .03), and (c) failure to deliver a radiation boost dose when tumor was present at the margin of the specimen (P = .002). The size of the tumor, the nodal status, the progesterone receptor assay result, and the presence of ductal carcinoma in situ mixed with infiltrating carcinoma did not show a significant influence on local recurrence. In 274 of 393 (70%) patients, cosmesis was evaluated. The four major factors affecting cosmesis favorably were (a) utilization of a wedge (P less than .0001); (b) treatment of two fields a day (P less than .0001); (c) failure to use a separate treatment port to the regional lymph nodes, so as to avoid field junctions (P = .0003); and (d) small size of specimen (less than 50 cm2) (P = .0171). A second or third cancer was found in 39 of the 393 (10%) patients; contralateral breast cancer was the most common form (n = 23), followed by genitourinary cancer (n = 5). The most frequent complication was arm edema (6%).

High dose rate 60Co remote afterloading irradiation in cancer of the cervix in Haiti, 1977-1984

From 1977 through 1984, 293 previously untreated patients with biopsy proven carcinoma of the uterine cervix were treated by whole pelvis irradiation and high intensity 60Co remote afterloading (RAL) intrauterine tandem techniques in Haiti. The treatment results were analyzed retrospectively to evaluate the therapeutic results and prognostic factors of a strict protocol involving 40 Gy to the whole pelvis (2 Gy/day, 5 days/week). In addition, on the 5th day of the 3rd week, the first outpatient 60Co remote afterloading intracavitary insertion, delivering 7.5 Gy to point "A" with each insertion, repeated 3 times by a week separation for a total of 4 times. The total TDF for external beam plus RAL was 158 and 175 for early and late effects respectively. One hundred-four patients were evaluable after 1 year or more follow-up, with a median of 26.5 months. No evidence of disease (NED) by Stage at 1 year was: Stage I of 100% (3/3), Stage II of 82% (9/11), Stage III of 80% (47/59), and Stage IV of 58% (18/31). The post-therapeutic complication rate was 7.7%, with no fistulas or requirement of surgical intervention. Those with documented follow-up of at least 2 years (74 patients) had comparable survival to other high dose rate and low dose rate studies. This study shows that outpatient brachytherapy can be carried out without sophisticated and expensive equipment with minimal staff trained in radiation therapy. A detailed description of this outpatient RAL technique and results are described so that this method can be adapted to other developing and industrialized nations where cost containment is becoming a key issue.

Treatment of a Down's syndrome patient for hyperthyroidism with radioactive iodine

A Down's syndrome patient was hospitalized for evaluation of vomiting, abdominal pain, and a history of weight loss. A subsequent workup revealed that she had hyperthyroidism. The treatment of choice was radioactive iodine therapy. The patient had a history of consistent nausea and incontinence for urine and feces. Special problems posed by the patient and radiation safety are discussed.

Intraoperative radiotherapy for intracranial malignancies. A pilot study

Intraoperative radiotherapy (IOR) or "direct view" irradiation permits the delivery of a single exposure of high-energy electrons to a surgically exposed tumor. Surgical exposure permits physical retraction of normal uninvolved tissues away from the IOR beam as well as the accurate assessment of the target volume. IOR represents a "supplement" or "boost" dose to conventional fractionated external beam irradiation that is administered postoperatively. This pilot study represents the clinical experience in the US using IOR for brain tumors. At Howard University Hospital, Washington, DC, 12 patients underwent surgical resection or decompression and 1500 cGy were delivered to the tumor bed intraoperatively. After surgical recovery, 5000 cGy in 25 fractions were delivered to the whole brain and an additional 500 cGy cone-down boost were delivered to the tumor bed. This protocol was best tolerated when the cranial vault was decompressed. Two patients with meningioma are without evidence apparently NED at 8, 11, 12, and 15 months, respectively. A fifth patient died at 8 months NED from an accident. Three glioma patients died with disease at 3, 13, and 15 months, respectively. Two additional patients died 30 days after surgery. Indications, techniques, and clinical findings are presented.