Computer planning of stereotactic iodine-125 seed brachytherapy for recurrent malignant gliomas

Controversies concerning the application of brachytherapy in central nervous system tumors

INTRODUCTION

Brachytherapy (BRT) is defined as a therapy technique where a radioactive source is placed a short distance from or within the tumor being treated. Much expectation has been placed on its efficacy to improve the outcome for patients with central nervous system (CNS) tumors due to the initial promising results from single institution retrospective studies. However, these optimistic findings have been highly debated since the selection criteria itself is preferable to other therapeutic modalities. The fact that BRT demonstrated no significant survival advantage in two prospective studies, together with the emerging role of stereotactic convergence therapy as a promising alternative, has further decreased the enthusiasm for BRT. Despite all the negative aspects, BRT continues to be conducted for the management of CNS tumors including gliomas, meningiomas and brain metastases.

MATERIAL AND METHODS

As many controversies have been aroused concerning the experience and future application of BRT, this article reviews the existing heterogeneities in terms of implants choice, optimal dose rate, targeting volume, timing of BRT, patients selection, substantial efficacy, BRT in comparison with stereotactic convergence therapy techniques and BRT in combination with other treatment modalities (data were identified by Pubmed searches).

RESULTS AND CONCLUSION

Though it is inconvincible to argue for the routine use of BRT, BRT may provide a choice for patients with large recurrent or inoperable deep-seated tumors, especially with the Glia-site technique. Radiotherapies including BRT may hold more promise if biologic mechanisms of radiation could be better understand and biologic modifications could be added in clinical trials.

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.

Head and neck tumors: fractionated frameless stereotactic interstitial brachytherapy-initial experience

The authors used a frameless stereotactic navigation system, the Vogele-Bale-Hohner head holder, and a targeting device to reproducibly position brachytherapy needles for fractionated interstitial brachytherapy in 12 patients with inoperable cancers of the head and neck. In all cases, deviations of the needle relative to the planned position were within 1-15 mm depending on the location of the tumor.

[First experiences with computer-assisted frameless stereotactic interstitial brachytherapy (CASIB)]

PURPOSE

To reach an optimal treatment result and to avoid damage to critical structures a homogeneous dose distribution in the tumor volume with a rapid decreasing dose to the surrounding structures is necessary. Fractionated interstitial brachytherapy of tumors in the ENT region employing needles depends on exact localization of the target volume during all fractions. Therefore reproducibility of positioning of the needle(s) plays an important role.

MATERIAL AND METHODS

We used the ISG Viewing Wand system in combination with the Vogele-Bale-Hohner (VBH) head holder and a new targeting device. Point of entrance, pathway, and target point of the needle were planned and insertion of the needle simulated in advance. To date we have treated 7 patients with inoperable tumors in the ENT region. The actual position of the needle in the control CT was compared to the planned position.

RESULTS

The accuracy of positioning of the needle depended on the location of the tumor. In a patient with a recurrent retroorbital adenocarcinoma the mean accuracy was 1 mm. Due to soft tissue displacement in the neck region and the resulting necessity to readjust the targeting device the needle was placed with a mean deviation of 15 mm between the planned and the actual position.

CONCLUSIONS

Computer-assisted frameless stereotactic interstitial brachytherapy allows for precise, reproducible and preplanned insertion of hollow needles into target structures closely adherent to the surrounding tissue, thus avoiding damage of neighbouring structures. This technique is of great advantage in treating deeply seated tumors which are fixed to bony structures, especially at the skull base. Inaccuracy in the neck region caused by soft tissue shift requires improvement of the immobilization in this region.

Radiation therapy in tumors of the central nervous system

OBJECTIVES

To review the role of radiation therapy in the management of primary tumors of the central nervous system (CNS).

DATA SOURCES

Book chapters, review articles, and research studies.

CONCLUSIONS

Radiation therapy plays an important role in the management of primary and metastatic tumors of the CNS. Radiation and surgery are combined with curative intent for low-grade tumors. Cranial radiation may be used to prevent brain metastases, and palliative radiation may be used to alleviate symptoms.

IMPLICATIONS FOR NURSING PRACTICE

Helping patients with tumors of the CNS and their family members understand the anticipated side effects of the disease and the therapeutic goals of radiation therapy may help to alleviate anxiety and maintain an optimal quality of life during therapy.

Retreatment of patients with intracranial gliomas by external beam radiotherapy and cytotoxic chemotherapy

Twenty-one patients with recurrent intracranial gliomas were retreated by external beam radiotherapy between 1987 and 1995. Twenty patients received cytotoxic chemotherapy involving CCNU as part of their retreatment. Only five of the 21 patients had received chemotherapy in combination with the initial external beam radiotherapy (RT) prior to recurrence. The different histological groups were analysed and the patients divided into two groups; group I (Grade I and II gliomas) and group II (Grade III, IV and glioblastoma). The overall median survival for all patients was 59 months, with a median survival of 22 months after recurrence. For group I and group II patients, the median survival was 26 months and 13 months after recurrence respectively. It was concluded that some highly selected patients with intracranial gliomas can be retreated safely by carefully planned external beam RT given to a relatively low dose in order to palliate neurological dysfunction and the symptoms of raised intracranial pressure, and to reduce steroid dependency. The results strongly suggest that recovery does occur after initial RT. Retreatment may possibly improve survival in a small proportion of patients. Further studies, including randomized trial designs, quality of life assessment, and neurological symptoms indices, would be required to determine the quantitative benefit of any such treatment policy. The objectives of this study were to determine whether patients received any benefit, such as symptom relief and the allowance of steroid withdrawal, after retreatment, and whether long term survival could be achieved.