Clinical Investigation
Minimized Doses for Linear Accelerator Radiosurgery of Brainstem Metastasis

https://doi.org/10.1016/j.ijrobp.2010.02.028Get rights and content

Purpose

Treatment of cerebral metastases located inside the brainstem remains a challenge, as the brainstem is considered to be a neurological organ at risk, whatever the treatment strategy. We report a retrospective study of 30 consecutive patients treated in our institution between 2005 and 2007 with micromultileaf linear accelerator (LINAC) –radiosurgery for brainstem metastases, with reduced doses compared to those usually reported in the literature.

Methods and Materials

Mean follow-up was 311 days (range, 41–1351). Median age was 57 years (range, 37–82), Mean Karnofsky Index (KI) was 80. Primary tumor site was lung (n = 13), breast (n = 4), kidney (n = 4), skin (melanoma; n = 3), and others (n = 6). Primary tumor was controlled in 17 cases; extracranial metastases were controlled in 12 cases. Mean number of metastases was 1.46 (one to three); median volume was 2.82 cc (0.06–18). Dose was delivered by a micromultileaf collimator 6-MV LINAC .

Results

Dose administered at the 70% isodose was 13.4 Gy (range, 8.2–15). Median survival was 10 months. Local control rates at 3, 6, and 12 months were 100%, 100%, and 79% respectively. Median neurological control duration was 5 months. Neurological control rates at 3, 6, and 12 months were 73%, 42%, and 25%, respectively. No parameter was found to significantly correlate with survival, local, or cerebral control. No patients had severe side effects (Grade III–IV), according to the Radiation Therapy Oncology Group (RTOG) scale.

Conclusion

Lower doses than previously reported can achieve the same local control and survival rates in brain metastases, with minimal side effects.

Introduction

Treatment of cerebral metastases located inside the brainstem remains a challenge as the brainstem is considered to be a neurological organ at risk 1, 2. Surgery in this area, despite improvements in microsurgical techniques and neuronavigation, is still risky and is mainly restricted to superficial lesions in contact with the fourth ventricle. When radiotherapy is planned, effectiveness is limited because high doses are excluded to avoid neurological deterioration 2, 3, 4, 5.

Radiosurgery, therefore has an increasing place in treatment strategy for cerebral metastases 6, 7, 8. To date, very few series of patients treated for brainstem lesions have been reported; the doses delivered were equivalent to those used for supratentorial locations, despite the debated tolerance of irradiation to this area 9, 10, 11, 12, 13, 14, 15. In fact, there are no guidelines indicating which dose should be delivered to avoid adverse effects resulting from brainstem injury.

We report a retrospective study of 30 consecutive patients treated in our institution between 2005 and 2007 for brainstem metastases with micromultileaf LINAC radiosurgery, with reduced doses compared with those usually reported in the literature.

Section snippets

Patients

Selection of patients, who were treated consecutively, was based on life expectancy (>3 months), general status (Karnofsky Index [KI] >50), and number (fewer than four lesions) and size (<4 cm diameter) of brain lesions. Patients were hospitalized for 3 days. Corticosteroids were administered intravenously the day of treatment. Clinical and magnetic resonance imaging (MRI) follow-up was performed at 1 month, then every 3 months. A tumor was considered as controlled if its volume was stable or

Results

Thirty patients were treated from 2005 to 2007. Mean follow-up was 311 days (range, 41–1351). Median duration between treatment of primary and radiosurgery was 645 days (range, 17–3,484). Median patient age was 57 (range, 37–82). Of the patients, 20 were men and 10 women. Karnofsky index, recursive partitioning analysis (RPA), score index of radiosurgery (SIR), and basic score for brain metastases (BS-BM) are described in Table 1 16, 17, 18.

Primary tumor site was lung (n = 13), breast (n = 4),

Discussion

Brainstem metastases remain a therapeutic challenge because of the brainstem's life-maintaining functions. A space-occupying process in this area can easily induce intracranial hypertension or neurological impairment. Moreover, brainstem lesions are considered to be rapidly lethal when not controlled. Therefore, local control may have a strong influence on survival, but available data are still contradictory 9, 10, 11, 12, 13, 14, 15. For Hussain et al. (11), local control rate was 100% for a

Conclusion

Brainstem metastases are known to be challenging lesions. They are difficult to control with conventional treatments but nevertheless require optimized local control before a significant influence on patient survival can be achieved. In our study, we show that reduced doses, compared with those usually administered, can achieve the same local control of brainstem lesions with no side effects. This could well minimize the risk of neurological deterioration, and could lead to possibilities for

References (29)

Cited by (35)

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    To enhance the management of metastatic brain tumors in the modern era, SRS and radiotherapy using radiosurgical modalities such as GK, CK, and Novalis have been developed to provide excellent local control with less toxicity in lieu of WBRT. Previous studies examining SRS or fSRT for BSM are summarized in Table 4.11-34 Huang et al.11 first assessed SRS for BSMs using GK in 1999.

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    Stereotactic radiosurgery (SRS) for brainstem metastases (BSM) has been shown to be a safe and effective modality.1-31 Reported rates of local tumor control in patients who received SRS for BSM vary from 74% to 100%, and the median survival ranges from 4 to 12 months.1-28,30,31 Despite the promising results of SRS with respect to local control and survival, toxicity due to radiation is always a concern, with severe to life-threatening toxicities being reported in 0%–9.5% of patients with BSM treated with SRS.2-10,12-14,16-18,20-28,30,31

  • Stereotactic Radiosurgery for Brainstem Metastases: An International Cooperative Study to Define Response and Toxicity

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    This realization has led some to use lower doses that are potentially ineffective for tumor control. Some reports of severe toxicity after brainstem SRS margin doses >16 Gy have led some authors to recommend avoiding doses this high (18, 26). Because of the small sample sizes, there was limited statistical power to associate SRS brainstem toxicity with tumor volume, location, margin dose, or previous WBRT.

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Conflict of interest: none.

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