Combined stereotactic split-course fractionated gamma knife radiosurgery and conventional radiation therapy for unfavorable gliomas: a phase I study

Radiobiology

New understandings of the biology of radiosurgery are considered. Differences from the radiobiology of fractionated radiotherapy are outlined. It is noted DNA damage alone is insufficient to account for the tissue changes which occur. Changes in blood vessels and immunological mechanisms are also involved. Tissue repair is more rapid than previously thought so that dose rate (the rate of delivery of radiation to the tissues) has been seen to be more important. The value of fractionation is examined. The effect of radiosurgery on normal brain (so called functional radiosurgery) is considered. The desired effects may be achieved by a focal stable destruction of brain from a high radiation dose. They may also be achieved using a lower dose which acts through the mechanism known as radiosurgical neuromodulation.

[Systematic review of stereotactic radiotherapy for high-grade gliomas]

The purpose of this literature systematic review was the use of stereotactic radiotherapy in glioma. Research was performed in Medline/PubMed and associated references found in published articles without publication date limit. The quality of series is variable and many biases can be evidenced. Only two randomized trials have been published using stereotactic radiotherapy for up-front treatment. There is a lack of evidence of survival advantages to use this treatment at the time of diagnosis or relapse. There is also insufficient evidence regarding the benefice/harms in the use of stereotactic fractionated radiation therapy for patients with glioma. No recommendations can be enounced. Stereotactic irradiation as boost in primary diagnosed glioma or relapsed tumour is not associated with survival improvement. For relapsed patients, treatment needs to be discussed according to the other treatment options.

Diffusion tensor imaging: possible implications for radiotherapy treatment planning of patients with high-grade glioma

AIMS

Radiotherapy treatment planning for high-grade gliomas (HGG) is hampered by the inability to image peri-tumoural white-matter infiltration. Diffusion tensor imaging (DTI) is an imaging technique that seems to show white-matter abnormalities resulting from tumour infiltration that cannot be visualised by conventional computed tomography or magnetic resonance imaging (MRI). We propose a new term, the image-based high-risk volume (IHV) for such abnormalities, which are distinct from the gross-tumour volume (GTV). For IHV based on DTI, we use the term IHVDTI. This study assesses the value of DTI for the individualisation of radiotherapy treatment planning for patients with HGG.

METHODS

Seven patients with biopsy-proven HGG were included in a theoretical planning exercise, comparing standard planning techniques with individualised plans based on DTI. Standard plans were generated using a 2.5 cm clinical target volume (CTV) margin added to the GTV. For DTI-based plans, the CTV was generated by adding a 1 cm margin to the IHVDTI. Estimates of normal tissue complication probability (NTCP) were calculated and used to estimate the level of dose escalation that could be achieved using the DTI-based plans.

RESULTS

The use of DTI resulted in non-uniform margins being added to the GTV to encompass areas at high risk of tumour involvement, but, in six out of seven cases, the IHVDTI was encapsulated by the standard CTV margin. In all cases, DTI could be used to reduce the size of the planning-target volume (PTV) (mean 35%, range 18-46%), resulting in escalated doses (mean 67 Gy, range 64-74 Gy), with NTCP levels that matched the conventional treatment plans.

CONCLUSION

DTI can be used to individualise radiotherapy target volumes, and reduction in the CTV permits modest dose escalation without an increase in NTCP. DTI may also be helpful in stratifying patients according to the degree of white-matter infiltration.

The American Society for Therapeutic Radiology and Oncology (ASTRO) evidence-based review of the role of radiosurgery for malignant glioma

PURPOSE

To systematically review the evidence for the use of stereotactic radiosurgery or stereotactic fractionated radiation therapy in adult patients with malignant glioma.

METHODS

Key clinical questions to be addressed in this evidence-based review were identified. Outcomes considered were overall survival, quality of life or symptom control, brain tumor control or response and toxicity. MEDLINE (1990-2004 June Week 2), CANCERLIT (1990-2003), CINAHL (1990-2004 June Week 2), EMBASE (1990-2004 Week 25), and the Cochrane library (2004 issue 2) databases were searched using OVID. In addition, the Physician Data Query clinical trials database, the proceedings of the American Society of Clinical Oncology (1997-2004), ASTRO (1997-2004), and the European Society of Therapeutic Radiology and Oncology (ESTRO) (1997-2003) were searched. Data from the literature search were reviewed and tabulated. This process included an assessment of the level of evidence.

RESULTS

For patients with newly diagnosed malignant glioma, radiosurgery as boost therapy with conventional external beam radiation was examined in one randomized trial, five prospective cohort studies, and seven retrospective series. There is Level I evidence that the use of radiosurgery boost followed by external beam radiotherapy and carmustine (BCNU) does not confer benefit with respect to overall survival, quality of life, or patterns of failure as compared with external beam radiotherapy and BCNU. There is Level I-III evidence of toxicity associated with radiosurgery boost as compared with external beam radiotherapy alone. The results of the prospective and retrospective studies may be influenced by selection bias. Radiosurgery used as salvage for recurrent or progressive malignant glioma after conventional external beam radiotherapy failure was reported in zero randomized trials, three prospective cohort studies, and five retrospective series. The available data are sparse and insufficient to make absolute recommendations. Stereotactic fractionated radiation therapy has been reported as boost therapy with external beam radiotherapy for patients with newly diagnosed malignant glioma in only three prospective studies. As primary therapy alone without conventional external beam radiotherapy for newly diagnosed malignant glioma patients, stereotactic fractionated radiation therapy has been reported in only one prospective study. There were only three prospective series and two retrospective studies reported for patients with recurrent or progressive malignant glioma.

CONCLUSIONS

For patients with malignant glioma, there is Level I-III evidence that the use of radiosurgery boost followed by external beam radiotherapy and BCNU does not confer benefit in terms of overall survival, local brain control, or quality of life as compared with external beam radiotherapy and BCNU. The use of radiosurgery boost is associated with increased toxicity. For patients with malignant glioma, there is insufficient evidence regarding the benefits/harms of using radiosurgery at the time progression or recurrence. There is also insufficient evidence regarding the benefits/harms in the use of stereotactic fractionated radiation therapy for patients with newly diagnosed or progressive/recurrent malignant glioma.

Survival trends in elderly patients with glioblastoma multiforme: resective surgery, radiation, and chemotherapy

BACKGROUND

It is appropriate to investigate and to determine survival trends following glioblastoma multiforme treatment using resective surgery, radiation therapy, and/or chemotherapy in patients aged 59 years and higher.

METHODS

We retrospectively reviewed 30 elderly patients (> or =59 years old) who were treated for histopathologically confirmed glioblastoma multiforme at our tertiary care institution from 1990 through 2002. All patients were treated with steroids. In addition, 22 patients underwent resective surgery (RS), 17 patients underwent radiation therapy (RT), and 10 patients underwent chemotherapy (C). Many patients underwent these treatments in various combinations: 6 underwent biopsy only, 7 RS only, 6 RS+RT only, and 9 RS+RT+C. For each case, pre-treatment Karnofsky performance scores (KPS), tumor location, presenting symptoms and signs, associated surgical morbidity, and pre-existing medical conditions were also recorded. Patients were categorized into one of four treatment subgroups: Biopsy only, RS only, RS+RT, and RT+RS+C. For each of these subgroups, pretreatment KPS and post-treatment survival were compared.

RESULTS

Post-treatment survival following biopsy only was 3.2 +/- 0.8 months (mean +/- SE); RS 2.2 +/- 0.5; RS+RT 5.5 +/- 1.2; RS+RT+C 13.6 +/- 2.1. A longer survival trend was noted for the RS+RT versus RS group (two-tailed unpaired t test, p = 0.02;), as well as the RS+RT+C group, which showed consistently higher survival in comparison to most of the other groups (p = 0.0021, 0.00039, 0.013 vs. the biopsy only, RS only, and RS+RT groups, respectively). No significant difference was found in KPS, comparing all individual groups versus each other (p > or = 0.06). Remarkably, 6 patients survived over 14 months (range, 14.1-22.7 months), all of which received RS+RT+C.

CONCLUSIONS

This study suggests a significant improvement in elderly patients treated with the combination of resective surgery, radiation therapy, and chemotherapy, rather than either treatment alone or other combination. This significant improvement does not appear to be biased by pretreatment KPS, as mean KPS values did not significantly differ between any of these groups. However, a greater number of patients in each group must be considered to achieve the power to make more definitive treatment guidelines.

The linear-quadratic model and fractionated stereotactic radiotherapy

PURPOSE

To determine the dose per fraction that could be used when gamma knife or linear accelerator-based stereotactic treatments are delivered in 2 or more fractions.

METHODS AND MATERIALS

The linear-quadratic (LQ) model was used to calculate the dose per fraction for a multiple-fraction regimen which is biologically equivalent to a given single-fraction treatment. The results are summarized in lookup tables.

RESULTS AND CONCLUSION

The tables can be used by practicing clinicians as a guide in planning fractionated treatment. For the large doses used in typical stereotactic treatments and for small fraction numbers, the model is not very sensitive to the value of the alpha/beta ratio in the LQ model. A simple rule of thumb is found that for two-fraction and three-fraction treatments the dose per fraction is roughly two-thirds and one-half of the single-fraction treatment dose, respectively.

Stereotactic radiosurgery in the management of intracranial gliomas

Glial neoplasms are the most common primary intracranial malignancies. Treatment of high-grade gliomas has been frustrating, with less than 5% of patients surviving 5 years after a diagnosis of glioblastoma multiforme (GBM). Stereotactic radiosurgery (SRS) and fractionated strereotactic radiotherapy (F-SRT) provide means to either escalate the dose in primary treatment or to palliate recurrences. Because of their lower alpha/beta ratios and more focal nature, low-grade gliomas (LGG) are more attractive targets for stereotactically focused radiation. Results of available phase I-II data are reviewed for both low and high-grade gliomas. In the case of high-grade gliomas disappointing preliminary phase III data from RTOG 93-05 are discussed. Toxicity of SRS is discussed. Acute treatment toxicity of significance is unusual and generally self-limited. Occasionally an exacerbation of existing symptoms occurs. Late complications attributable to SRS are usually defined as necrosis within the treatment volume. The rate of necrosis can be hard to define in high-grade gliomas as tumor cells are often present in surgical specimens. New strategies in the application of stereotactic radiation are touched upon, these include: changes in planning and fractionation, concurrent use of chemotherapy, use of radiation modifiers and biologic agents. After reviewing the current data for high-grade gliomas, it appears that any apparent improvement in outcome seen in phase I-II trials is attributable to patient selection. The best evidence available does not support the use of SRS for primary high-grade gliomas. The somewhat limited experience in LGG also indicates a lack of benefit for patients treated with stereotactic radiosurgery or F-SRT. For a very select group of patients with small recurrent lesions, F-SRT may represent a safe, reasonable treatment.

The radiation oncologist's perspective on stereotactic radiosurgery

Unfavorable gliomas: The basis for single-fraction stereotactic radiosurgery (SRS) is largely historical in nature and rooted in conventional thinking. This is derived from the original use of SRS in the treatment of arteriovenous malformations (AVMs), where the benefit of single-fraction high-dose radiation is clearly optimal in terms of addressing AVM obliteration kinetics. However, tumor cell kinetics are not the same as AVM obliteration kinetics and therefore may not be optimally addressed by single-fraction SRS. In addition, fractionated (F) SRS, as compared to single-fraction SRS, should allow for sparing of normal tissue damage. The relatively noninvasive nature of SRS allows for the potential of exploiting the use of FSRS and also allows for consideration of delivering FSRS in a split-course fashion. This provides an additional advantage over what can normally be achieved by use of stereotactic brachytherapy, in that sterotactic brachytherapy is likely to be performed only once in the course of a patient's primary treatment. This strategy exploits tumor and/or normal tissue cell kinetics, inclusive of attempting to counteract the initial accelerated tumor growth phase pre-CEBRT(conventional external beam radiation therapy), thereby decreasing the rate of clinical tumor progression during CEBRT. This split-course design should also help to counteract the effect of accelerated tumor repopulation post-CEBRT. Our unique experience with this approach in patients with unfavorable gliomas will be reviewed. Brain metastases: While whole brain radiation therapy (WBRT) remains a standard of care in patients with brain metastases, is potential neurocognitive morbidity remains a poorly understood concern. Despite this, and with an increasing role of surgery and/or SRS in the primary management of patients with brain metastasis, recently reported experiences withholding WBRT as part of primary therapy for brain metastases have not analyzed the potential effects on neurological functional status and/or neurocognition associated with the increased risk of brain tumor recurrence seen with such a strategy. We recently evaluated the risk of symptomatic brain tumor recurrence and associated neurologic deficit in 36 patients treated for newly diagnosed unresected brain metastases treated by Gamma Knife SRS alone followed by planned observation. Among the 17 patients (47%) developing brain tumor recurrence, 71% (12/17) were symptomatic and 59% (10/17) had an associated neurologic deficit. Also of interest, the author (WFR) performed a secondary analysis of a randomized phase III study of accelerated hyperfractionation (AH) versus standard accelerated fractionation (AF) in patients with unresected brain metastases. Control of brain metastases had a significant impact on MMSE. It is only among patients with 'uncontrolled" brain metastases that a drop in MMSE score is seen. Details of these studies, along with others, will be reviewed and implications with regards to the complementary role of WBRT in patients undergoing SRS for brain metastases will be discussed.