Interstitial radiobrachytherapy of malignant cerebral neoplasms: rationale, methodology, prospects

The Invention and Early History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin of the N-localizer, presents recently discovered evidence that documents its history, and corrects misconceptions related to its origin and early history.

The Origin and History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin and early history of the N-localizer and corrects some misconceptions related to both.

Combined treatment of rituximab, idarubicin, dexamethasone, cytarabine, methotrexate with radiotherapy for primary central nervous system lymphoma

The overall response rates and long-term survival of primary central nervous system lymphoma (PCNSL) are still significantly inferior to the results achieved in similar subtypes of extranodal non-Hodgkin's lymphoma. It is clearly necessary to investigate new therapeutic methods on PCNSL. We encountered three patients histologically documented PCNSL as diffuse large B-cell lymphoma (DLBCL). They were treated with R-IDARAM which comprised rituximab, idarubicin, dexamethasone, cytarabine and methotrexate. Patient 1 received stereotactic brachytherapy (SBT) prior to chemotherapy performed with iodine-125 seeds (cumulative therapeutic dose 50 Gy). After six cycles of R-IDARAM at 3-weekly intervals, radiotherapy was applied at a dosage of 2000–4000 cGy in conventional schedule (180 or 200 cGy/day) to whole brain or spinal cord in all patients. Complete remission (CR) was achieved after first two cycles of R-IDARAM in all patients. All three patients remained in CR at the time of this report with a median duration of follow-up of 23 months (ranging from 13 to 41 months). Three patients have been alive for 41, 13, 16 months respectively until now. The patient with the longest survival time was the one given SBT prior to chemotherapy. This study suggests that R-IDARAM combining with radiotherapy maybe a high effective regimen in PCNSL patients especially those with primary central nervous system DLBCL. A comprehensive treatment combining internal radiotherapy by SBT, modified R-IDARAM and followed reduced external radiotherapy may be a new treatment concept for PCNSL with higher efficiency and lower toxicity.

Interstitial stereotactic radiosurgery

Stereotactic radiosurgery by means of interstitial application of either radionuclides or radiation devices has been used extensively in primary and secondary brain tumors. A few centers have gained sufficient expertise and clinical data to scientifically evaluate this treatment modality. Interstitial stereotactic radiosurgery is limited to circumscribed lesions with a diameter of 3.5 cm or less. The radiobiology of interstitial radiosurgery is quite well elaborated as to doses, dose rates and effects on vascular physiology. Efficacy in low grade gliomas is well documented by several European centers using 125-J sources. Different modes of implantation have been used and evaluated including single fraction treatment using a miniature linear accelerator (Photoelectron). In malignant gliomas interstitial radiosurgery has been investigated in a prospective, randomised, controlled trial and not shown to be effective. Steretactic interstitial radiosurgery is a powerful treatment option in circumscribed CNS tumors like some low grade gliomas and metastasis but does play no major role in the treatment of malignant glioma.

Exophytic malignant brainstem mixed glioma in an adult: a case report

Anaplastic mixed gliomas are rare tumors that occur mostly in the cerebral hemispheres. They have a distinctive histological appearance characterized by the presence of two or more glial cellular constituents. The incidence of malignant mixed glioma of the brainstem and posterior fossa is extremely low. The authors report an unusual case of an exophytic malignant mixed glioma. Following subtotal resection, the patient received conventional radiotherapy, but continued to deteriorate, and died five months after surgery. The extensive literature review focuses on histopathology, clinical features, natural history, and possible treatment modalities of this unusual neoplasm.

Intraoperative radiotherapy for gliomas

Intraoperative radiotherapy (IORT) was performed in 20 of 36 patients with glioma; 11 glioblastomas, 7 malignant astrocytomas, 2 benign astrocytomas. Twenty or 25 Gy of irradiation was delivered in a single fraction intraoperatively, followed by external beam irradiation. The electron beam energy was selected so that the 80% isodose line fell at 2 or 3 cm below the residual tumor surface. Median survival time of IORT group was 14 months and that of the control group was 10 months. Difference of survival curve was significant. There were 6 incidences of complication caused by IORT; 1 radionecrosis, 1 convulsion, 1 abscess, and 3 severe brain edemas. IORT is suited for the treatment of malignant gliomas.

High activity iodine-125 interstitial implant for gliomas

A total of 307 adult patients with glioma were treated with high-activity removable iodine-125 interstitial brain implants at the University of California at San Francisco from December 1979 to June 1990. Recurrent gliomas underwent brain implant alone whereas previously untreated (primary) tumors underwent brain implant boost after external beam radiotherapy. Of these patients, 106 had primary glioblastoma multiforme, 68 had primary non-glioblastoma glioma, 66 had recurrent glioblastoma multiforme and 67 had recurrent nonglioblastoma glioma. Median follow-up for living patients was 143 weeks. Median survival from diagnosis for primary glioblastoma multiforme and high and low grade nonglioblastoma glioma was 88 weeks, 142 weeks, and 226 weeks, respectively. Median survival measured from the date of implant for recurrent glioblastoma multiforme and high and low grade nonglioblastoma glioma was 49 weeks, 52 weeks, and 81 weeks, respectively. Ninety-two percent of patients had no toxicity or transient acute side effects. Severe acute toxicity was seen in 6% of patients, life threatening acute toxicity in 1% of patients, and fatal toxicity in less than 1% of patients. Forty percent of patients with malignant glioma underwent reoperation at a median of 33 weeks after brain implant, with tumor found in 95% of specimens at reoperation. This large experience demonstrates that interstitial implant is well-tolerated and prolongs survival in patients with primary and recurrent glioblastoma multiforme, as evidenced by the 3-year survival rates of 22% and 15%, respectively.

Treatment results of stereotactic interstitial brachytherapy for primary and metastatic brain tumors

A total of 41 stereotactic interstitial brain implants in 39 patients were performed for recurrence after teletherapy (recurrence implant), or as part of initial treatment in conjunction with teletherapy (primary implant). Implanted tumors consisted of malignant gliomas (33), other primary brain tumors (3), and single metastatic lesions (3). All patients were temporarily implanted with Ir-192 using a coaxial catheter afterloading system; two patients were implanted twice. Survival post-implant for glioblastoma multiforme (GBM), 13 patients, was 10 months whether implanted primarily or for recurrence. Mean time to recurrence, measured from initiation of teletherapy to implantation, was 10 months. Twenty patients with anaplastic astrocytoma (AA) had a median survival post-implant of 23 months for primary implants (7 patients) and 11 months for recurrence implants (13 patients). Mean time to recurrence, measured from initiation of teletherapy to implantation, was 19 months. Three patients (9%) of the evaluable group required reoperation for symptomatic mass effect, all with initial diagnosis of AA. Survival for this subgroup was 14, 22, and 32 months post-implantation. Using stereotactic techniques, interstitial brachytherapy of brain tumors was technically feasible with negligible acute morbidity and mortality, and appeared to offer limited prolongation of control for a subset of patients with recurrent malignant gliomas. The role of this modality in primary treatment for malignant gliomas needs to be further defined by prospectively randomized trials.

Interstitial radiogold implantation for the treatment of recurrent high-grade gliomas

Thirty-three patients were treated at the Methodist Hospital, Baylor College of Medicine (Houston) between 1983 and 1987, for high-grade gliomas which had recurred after conventional external-beam radiation therapy. The mean dose to the tumor volume from the external-beam therapy was 5800 cGy. Thirteen patients had recurrent astrocytoma Grade 4 (glioblastoma), whereas 20 had recurrent astrocytoma Grade 3 (anaplastic astrocytoma). All patients were treated for their recurrence by the combination of reexcision of as much of the tumor mass as was technically feasible and intraoperative radiogold (198Au) seed implantation of the residual tumor and/or tumor bed. The mean dose to the tumor volume from the implant was 4000 cGy. For the 13 patients treated for recurrent glioblastoma the 1-year, 2-year, and 3-year survival rates were 46%, 15%, and 8%, respectively. For the 20 patients treated for recurrent anaplastic astrocytoma the 1-year, 2-year, and 3-year survival rates were 75%, 50%, and 15%, respectively. Survival was measured from the time of implant. The median survival for patients with glioblastoma was 9 months. The median survival for patients with anaplastic astrocytoma was 17 months. One patient died in the immediate postoperative period from a gastrointestinal bleed. No patient required reoperation for radiation necrosis. The authors believe that this technique is an effective treatment for patients with high-grade gliomas recurring after external-beam radiation therapy, and are now including interstitial irradiation in the initial management of selected patients with high-grade gliomas.

A CT-based computerized treatment planning system for I-125 stereotactic brain implants

A computer program has been developed at the University of California, San Francisco, as an aid in planning and evaluating stereotactic brain implants made with 125I seeds. The program allows images of seeds and catheters to be positioned in the target volume revealed by CT. It then generates and displays the resulting isodose distributions. Catheters may be changed interactively until an optimum implant is achieved. From the geometry of a stereotactic implant frame as measured by CT, the program calculates the approach angles of the catheters in the frame coordinate system. After the seeds are implanted, films made with a fiducial marker box can be used to generate true seed positions and hence true isodoses. This paper describes mathematically the geometrical transformations used by the program, and also outlines its many features and options. In its first 2 years of use the program has proved to be a valuable contributor to improved patient care.

Stereotaxic irradiation of brain tumors

Stereotaxic techniques may be used in combination with interstitial or external beam radiotherapy for the treatment of intracranial malignancies. At the University of California, San Francisco, temporary, high-activity, iodine 125 sources are used mainly for the treatment of malignant gliomas. Patients with unifocal lesions that are smaller than 5 to 6 cm have discrete margins on computed tomography (CT) limited to supratentorial regions are selected for stereotaxic implantation. Both primary and recurrent malignant gliomas are treated with stereotaxic implantation; primary malignant gliomas are treated in addition with nonstereotaxic external beam radiotherapy and concomitant and sequential chemotherapy. Median survival times measured from the time of implantation are as follows: primary glioblastoma multiforme, 95 weeks; recurrent glioblastoma multiforme, 54 weeks; primary anaplastic astrocytoma, 223 weeks; and recurrent anaplastic astrocytoma, 81 weeks. Stereotaxic interstitial brachytherapy in conjunction with hyperthermia (thermoradiotherapy) is being studied in the treatment of recurrent or metastatic intracranial malignancy. External beam radiotherapy delivered stereotaxically in a single fraction (radiosurgery) has been used mainly for benign intracranial processes, although several centers are now exploring its use in the management of highly selected malignant lesions. Although its role is not yet completely defined, it may prove useful in highly selected subsets of patients with small intracranial malignancies, whether primary, recurrent, or metastatic.

Survival and quality of life after interstitial implantation of removable high-activity iodine-125 sources for the treatment of patients with recurrent malignant gliomas

Between January 1980 and January 1988, 95 evaluable patients with recurrent, unifocal, supratentorial malignant gliomas were reirradiated with high-activity iodine-125 sources implanted directly into tumor in afterloaded, removable catheters using computerized tomography-directed stereotaxy. A tumor dose of 5270-15,000 cGy was delivered at a maximum distance of 0.5 cm from the rim of the contrast-enhancing mass seen on CT scans. The median survival for the 50 patients with anaplastic astrocytoma was 81 weeks and for 45 patients with glioblastoma multiforme it was 54 weeks. The 18- and 36-month survival rates for patients with anaplastic astrocytoma were 46% and 28%, respectively; the 18- and 36-month survival rates for patients with glioblastoma multiforme were 22% and 8%, respectively. Because of clinical deterioration, increasing steroid dependency, and increasing mass effect at the implantation site seen on CT scans, necrotic tissue was excised from 47 patients (49%) at craniotomy; in some patients, tumor was mixed with necrotic tissue. The survival of reoperated patients was significantly longer compared with patients who did not undergo this procedure. Serial determination of the Karnofsky Performance Score (KPS) showed that there was no significant deterioration for the group as a whole during the 6 months immediately after implantation. At 18 months, 33 of the patients were alive; KPS ranged between 50 to 90 (mean 79) and 67% were steroid dependent. At 36 months, 18 patients were alive; 17 patients were evaluable with KPS that ranged between 40 to 90 (mean 76) and 53% were steroid dependent. Eleven of the 17 evaluable long-term survivors had a KPS of 80 or higher with a mean of 87. Interstitial brachytherapy may provide long-term survival in selected patients with recurrent malignant gliomas who have been irradiated previously with conventional teletherapy. The quality of life in the majority of long-term survivors appears to be quite satisfactory. Further attempts to control tumor growth using this modality appear to be warranted.

Paediatric brachytherapy. II. Brain implantation

The case histories of four children with brain tumours, for whom stereotactic brachytherapy was indicated, are presented from the St Bartholomew's Hospital intracranial brachytherapy programme. The recent evolution of the computed-tomography-directed stereotactic technique is described and the uses of different radionuclides (198Au, 192Ir) are discussed. The future of brachytherapy for paediatric brain tumours is debated.