Interstitial iridium-192 implantation for malignant brain tumours. Part II: Clinical experience

Brachytherapy for brain tumors

Over the past several decades neurooncologists have attempted to find an adjuvant treatment that prolongs survival for patients with malignant brain tumors. Brachytherapy, radiotherapy delivered by placing radioactive sources directly into the tumor, was initially thought to be the solution to this problem. Initial single institution studies showed very promising results; however, this technique has failed to show a significant survival advantage in two randomized studies. Despite this, brachytherapy continues to be used in a number of centers throughout the world for the treatment of various types of brain tumors including low-grade gliomas, anaplastic astrocytomas, glioblastomas, meningiomas and metastases. This article reviews brachytherapy's rationale, radiobiology, complications, indications, and results from numerous studies that have focused on its application for brain tumors with emphasis on its application for glial tumors.

Radiation therapy of the older patient

Radiotherapy has a major role in the multidisciplinary approach to cancer therapy. It is widely used for curative and palliative treatment of cancer involving various sites. Radiotherapy is of particular benefit to older and frail cancer patients as an alternative to surgery and to systemic therapy. The available data on the sensitivity of normal tissues to radiotherapy in elderly patients strongly suggest that older patients with good functional status tolerate radiotherapy as well as younger patients and have comparable tumor response and survival rates. Aggressive radiotherapy should not be withheld from older patients because of chronological age alone.

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.

[Radiotherapy of glioblastoma]

Glioblastoma cells appear to be inherently radioresistant and to present a significant fraction of hypoxic cells. The most significant prognostic factors to compare results achieved in several series of patients are the age, performance status and quality of surgical resection. Several randomized trials have provided evidence supporting the efficacy of radiation therapy in the treatment of glioblastoma. Prescription of a 60-Gy dose delivered according to a conventional dose-fractionation scheme (single daily fractions of 1.7 to 2 Gy five times per week) in a target volume with a 2-3 cm margin of tissue surrounding the perimeter of the contrast enhancing lesion on computerized tomography and magnetic resonance imaging is derived from observations made in several retrospective and prospective studies. Evidence of improvement in survival was observed neither in patients receiving hyperfractioned and accelerated radiotherapy, nor in patients for whom radiation sensitizers such as nitroimidazole compounds or halogenated pyrimidine analogs were associated to radiation therapy. The addition of nitrosourea to radiotherapy increases the 2-year survival rate by about 10%. Combination of full-dose external beam radiotherapy and brachytherapy or radiosurgery boost in selected patients with glioblastoma leads to an increase in the median survival, while external beam radiation alone in patients with similar prognosis does not.

Quality-adjusted survival analysis of malignant glioma patients

The goal of therapeutic intervention in oncology patients is to prolong survival without compromising its quality. Definition and measurement of quality are quite difficult. This article discusses the statistical techniques for quantifying quality survival that have been used in brain tumor patients. These techniques assume either that all patients have equivalent baseline quality of life when both disease-related symptoms and toxicities are absent, or that the length of time with a predetermined level of impairment is equivalent to death. These models do not fit the heterogeneous symptoms experienced by patients with malignant brain tumors. We propose a model that incorporates the baseline states with transitions to different levels of severity that indicate improvement and/or declines in physical and cognitive functioning of brain tumor patients. The length of time spent in each state is observed and weighted by using predetermined utilities. The weighted time spent in each state is aggregated over all states into a quality-time of survival metric (QTIME). This QTIME model was applied to a previously published, randomized clinical trial of different radiation doses in malignant brain tumor patients.

Radiosurgery and accelerated radiotherapy for patients with glioblastoma

OBJECTIVE

To assess the feasibility, toxicity, and local control of stereotactic radiosurgery followed by accelerated external beam radiotherapy (AEBR) for patients with glioblastoma multiforme.

MATERIALS AND METHODS

Six males and eight females, with a median age of 67.5 years (range 45-78 years), entered the study. Karnofsky performance status was 90 for five, 80 for six, and 60 for three patients. Following surgery, the patients were left with a residual mass 4 cm. Radiosurgery was delivered with a single dose of 20 Gy to the 90% isodose surface corresponding to the contrast-enhancing edge of the tumour. A total AEBR dose of 60 Gy in 30 fractions was delivered using a concomitant boost technique over four weeks.

RESULTS

Median survival time was 40 weeks (range 17-80 weeks). Actuarial survivals at 12 and 18 months were 43% and 14%, respectively. The median time to progression was 25 weeks (range 2-77 weeks). One patient developed a seizure on the day of stereotactic radiosurgery. Two patients experienced somnolence at 47 and 67 days post-radiotherapy. Eight patients remained steroid-dependent. Radiological evidence of leukoencephalopathy was observed in one patient, and brain necrosis in two additional patients at 30 and 63 weeks. One of these two patients with brain necrosis developed complete loss of vision in one eye, and decreased vision in the contralateral eye at 63 weeks.

CONCLUSION

Stereotactic radiosurgery followed by AEBR was feasible but was associated with late complications. The use of such radiosurgical boost for patients with glioblastoma multiforme should be reserved for those patients entering controlled clinical trials.

Interstitial brachytherapy procedures for brain tumors

Promising results have been obtained using brachytherapy in the treatment of brain tumors. Very low-dose rate brachytherapy (60-100 Gy given at 0.05-0.10 Gy/h) has been used for low-grade gliomas, resulting in 5- and 10-year survival probabilities of 85% and 83% for pilocytic astrocytomas and 61% and 51% for grade II astrocytomas. Only 2.6% of patients had symptomatic radiation necrosis. For faster-growing high-grade gliomas, temporary implants delivering about 60 Gy at 0.40-0.60 Gy/h are generally used. The largest series have reported median survival times of 12-13 months after brachytherapy for recurrent malignant gliomas and 18-19 months after diagnosis of primary glioblastomas treated with external beam radiotherapy and brachytherapy boost. A recent prospective, randomized trial demonstrated significantly improved survival for high-grade glioma patients who had brachytherapy boost. However, over 50% of patients who undergo brachytherapy for malignant gliomas require reoperation for tumor progression and/or radiation necrosis. Strategies are under development to improve local control without increasing radiation toxicity.

Brachytherapy for recurrent malignant astrocytoma

PURPOSE

To assess the efficacy of interstitial brachytherapy in the treatment of patients with recurrent malignant astrocytoma.

METHODS AND MATERIALS

Forty-six patients with recurrent malignant astrocytoma were treated with stereotactic high-activity temporary iodine-125 implants between September, 1986 and October, 1992. All patients had been initially treated for malignant astrocytoma (44) or low-grade astrocytoma (2) with surgery and external fractionated radiation. The median time between initial diagnosis and recurrence treated with brachytherapy was 12.5 months. Twenty-five patients received chemotherapy prior to brachytherapy.

RESULTS

All but four patients have died; median survival time following brachytherapy is 46 weeks. Twelve patients underwent reoperation for radiation necrosis at a median interval of 6.5 months after treatment (26%). Five patients incurred complications directly due to brachytherapy (11%). Forty-four patients are evaluable regarding pattern of failure following brachytherapy. Six of these 44 patients (13.6%) recurred at a distance from the treatment volume (4 in brain and 2 in spinal subarachnoid space).

CONCLUSION

Brachytherapy confers modest but meaningful prolongation of survival in selected patients with recurrent malignant astrocytoma, but complications are significant, reoperation frequently required, and recurrence outside the treatment volume common.

Long term results of stereotactic brachytherapy used in the initial treatment of patients with glioblastomas

BACKGROUND

Despite optimal therapy with surgery and radiotherapy, the prognosis of patients with glioblastomas remains poor. Stereotactic brachytherapy involves the accurate placement of radioactive isotopes within brain tumors, significantly increasing the dose of radiation that can be delivered to the tumor bed without substantial risk to surrounding normal tissue, potentially improving local tumor control and patient survival.

METHODS

Between February 1987 and July 1993, the authors treated 56 patients with glioblastomas with stereotactic brachytherapy as part of their initial therapy. Patients underwent surgery, limited field external beam radiotherapy, and brachytherapy with temporary high-activity iodine 125 sources, giving an additional 50 Gy to the tumor bed.

RESULTS

Median survival for patients undergoing brachytherapy was 18 months compared with 11 months for a matched brachytherapy control group with similar clinical and radiologic features (P < 0.0007). Survival rates at 1, 2, and 3 years after diagnosis of 83%, 34%, and 27%, respectively, for patients receiving brachytherapy were significantly increased compared with survival rates of 40%, 12.5%, and 9%, respectively, for control subjects. Thirty-six patients (64%) underwent reoperation for symptomatic radiation necrosis from 3 to 42 months (median, 11 months) after brachytherapy. The median survival of patients undergoing reoperation was 22 months compared with 13 months for those who did not have further surgery (P < 0.02). Thirty-five percent of patients relapsed locally within the brachytherapy target volume, whereas 65% had marginal or distant relapses.

CONCLUSIONS

Brachytherapy may improve local tumor control and prolong survival when used in the initial treatment of selected patients with glioblastomas.

Resection for solitary brain metastasis. Role of adjuvant radiation and prognostic variables in 229 patients

The authors reviewed 229 consecutive patients treated intramurally by resection of solitary cerebral metastasis. Patients were classified into four groups on the basis of whether a gross total resection or subtotal resection was performed and whether systemic disease was present or absent at the time of craniotomy. Group 1 had gross total resection and no systemic disease; Group 2 had subtotal resection and no systemic disease; Group 3 had subtotal resection and systemic disease; and Group 4 had gross total resection and systemic disease. All four groups were further subdivided into Subgroup A (adjuvant whole-brain radiation therapy) or Subgroup B (no adjuvant radiation). Data were collected regarding multiple patient and tumor variables for multivariate analysis. Survival data for the 46 patients in Group 1A (median 1.3 years, 2-year survival rate 41%, 5-year survival rate 21%) were markedly better than those for the 75 in Group 1B (median 0.7 year, 2-year survival rate 19%, 5-year survival rate 4%). The 20 patients in Group 2A also had superior survival data (median 1.1 years, 2-year survival rate 30%, 3-year survival rate 30%) when compared with the eight patients in Group 2B (median 3 months, 1-year survival rate 0%). However, the 16 and 22 patients in Groups 3A and 4A, respectively, had no discernible differences compared to the seven and 35 patients in their Group 3B and 4B counterparts. Multivariate analyses were performed to assess the association of survival with multiple patient, disease, and treatment variables. Poor neurological status and systemic disease were significantly associated with inferior survival, while longer (greater than 36 months) intervals between primary diagnosis and craniotomy were significantly associated with improved survival. After adjusting for the effects of other patient, disease, and treatment characteristics, adjuvant whole-brain radiotherapy was significantly associated with improved survival times. These data support the continued use of craniotomy followed by adjuvant whole-brain radiation therapy for treatment of solitary brain metastasis. However, this aggressive therapy appears relatively contraindicated in the face of either systemic disease or substantial neurological deficit.

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.

A Medical Research Council trial of two radiotherapy doses in the treatment of grades 3 and 4 astrocytoma. The Medical Research Council Brain Tumour Working Party

A total of 474 adult patients with malignant glioma (astrocytoma) grade 3 or 4 were randomised into an MRC study (BR2) comparing 45 Gy (in 20 fractions over 4 weeks) with 60 Gy (in 30 fractions over 6 weeks) of radiotherapy given post-operatively. Using 2:1 randomisation, 318 patients were allocated the 60 Gy course and 156 the 45 Gy course. Adjuvant chemotherapy was not given. The results show that a 60 Gy course produces a modest lengthening of progression-free and overall survival. They suggest a statistically significant prolongation of median survival from 9 months in the 45 Gy group to 12 months in the 60 Gy group (hazard ratio = 0.75, chi 2 = 7.36, d.f. = 1, P = 0.007). Over 80% of patients reported no morbidity from the radiotherapy, and there was no evidence of increased short-term morbidity in the higher dose group. Late morbidity was not assessed. A prognostic index defined in a previous MRC study was validated in this new cohort. It identifies a group of patients (20% of the total) with a 2 year survival rate of 28% (95% confidence interval 19% to 38%). It was apparent that the survival advantage to the higher dose was maintained even in the poorest prognostic groups defined by this index.

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.

Clinical considerations for neutron capture therapy of brain tumors

The radiotherapeutic management of primary brain tumors and metastatic melanoma in brain has had disappointing clinical results for many years. Although neutron capture therapy was tried in the United States in the 1950s and 1960s, the results were not as hoped. However, with the newly developed capability to measure boron concentrations in blood and tissue both quickly and accurately, and with the advent of epithermal neutron beams obviating the need for scalp and skull reflection, it should now be possible to mount such a clinical trial of NCT again and avoid serious complications. As a prerequisite, it will be important to demonstrate the differential uptake of boron compound in brain tumor as compared with normal brain and its blood supply. If this can be done, then a trial of boron neutron capture therapy for brain tumors should be feasible. Because boronated phenylalanine has been demonstrated to be preferentially taken up by melanoma cells through the biosynthetic pathway for melanin, there is special interest in a trial of boron neutron capture therapy for metastatic melanoma in brain. Again, the use of an epithermal beam would make this a practical possibility. However, because any epithermal (or thermal) beam must contain a certain contaminating level of gamma rays, and because even a pure neutron beam causes gamma rays to be generated when it interacts with tissue, we think that it is essential to deliver treatments with an epithermal beam for boron neutron capture therapy in fractions in order to minimize the late-effects of low-LET gamma rays in the normal tissue. I look forward to the remainder of this Workshop, which will detail recent progress in the development of epithermal, as well as thermal, beams and new methods for tracking and measuring the uptake of boron in normal and tumor tissues.

Interstitial iridium-192 implantation for malignant brain tumours. Part II: Clinical experience

The treatment results of 37 patients with malignant brain neoplasms treated with a computed-tomography-guided stereotactic iridium-192 implant are reviewed. Of these, 29 patients with high-grade gliomas (20 with glioblastoma multiforme (GBM), nine with anaplastic astrocytoma (AA] received an implant as part of their initial management. The median survival was 14.5 and 15.5 months in the patients with previously untreated GBM and AA, respectively. In those patients with recurrent tumour after external-beam irradiation, durable local control over a year was achieved with implantation. Increasing the total tumour dose from 120 to 160 Gy did not improve survival or local control. Karnofsky Performance Status (KPS) was used as an indicator of quality of life and was seen to decrease with a median interval of 8.5 months following treatment. No severe complications were noted in the entire group of patients treated with this implant procedure.

Interstitial iridium-192 implantation for malignant brain tumours. Part I: Techniques of dosimetry planning

Interstitial implants for brain tumours with removable iridium-192 radioactive seeds have been performed using a Brown-Roberts-Wells stereotactic frame. A simple and accurate computed-tomography-guided dosimetry pre-planning technique and procedure prior to implant have been developed and are discussed.