μMLC-LINAC radiosurgery for intracranial meningiomas of complex shape

Linear Accelerator-Based Radiosurgery of Grade I Intracranial Meningiomas

Objective

To determine the local control rate and complication rate in the treatment of grade I intracranial meningiomas.

Methods

A retrospective study was performed of patients with grade I meningioma who received radiosurgery with a dedicated linear accelerator from January 2002 to August 2012 with a minimum follow-up of 2 years. We performed descriptive statistics, logistic regression, and progression-free survival analysis through a Kaplan-Meier curve.

Results

Seventy-five patients with 78 grade I meningiomas received radiosurgery, 39 underwent surgery plus adjuvant radiosurgery, and 36 only radiosurgery. The follow-up median time was 68 months (range, 35–120 months). The tumor control rate was 93%, the 5-year progression-free survival was 92% (95% confidence interval, 77%–98%). Acute toxicity was 2.6%, and grade 1–2 late toxicity was 26.6%. Postradiosurgery edema was the main late morbidity. Age >55 years was the only significant factor for attaining a response >75%. The background of surgery before radiosurgery was the only significant prognostic factor for showing edema (odds ratio 5.78 [95% confidence interval, 2.14–15.64]).

Conclusions

The local control rate attained in our series is similar to that reported in other series worldwide; the acute toxicity rate was low and late toxicity was moderate.

Survival of Patients with Primary Brain Tumors: Comparison of Two Statistical Approaches

Purpose

We reviewed the survival time for patients with primary brain tumors undergoing treatment with stereotactic radiation methods at the Masaryk Memorial Cancer Institute Brno. We also identified risk factors and characteristics, and described their influence on survival time.

Methods

In summarizing survival data, there are two functions of principal interest, namely, the survival function and the hazard function. In practice, both of them can depend on some characteristics. We focused on nonparametric methods, propose a method based on kernel smoothing, and compared our estimates with the results of the Cox regression model. The hazard function is conditional to age and gross tumor volume and visualized as a color-coded surface. A multivariate Cox model was also designed.

Results

There were 88 patients with primary brain cancer, treated with stereotactic radiation. The median survival of our patient cohort was 47.8 months. The estimate of the hazard function has two peaks (about 10 months and about 40 months). The survival time of patients was significantly different for various diagnoses (p≪0.001), KI (p = 0.047) and stereotactic methods (p = 0.033). Patients with a greater GTV had higher risk of death. The suitable threshold for GTV is 20 cm³. Younger patients with a survival time of about 50 months had a higher risk of death. In the multivariate Cox regression model, the selected variables were age, GTV, sex, diagnosis, KI, location, and some of their interactions.

Conclusion

Kernel methods give us the possibility to evaluate continuous risk variables and based on the results offer risk-prone patients a different treatment, and can be useful for verifying assumptions of the Cox model or for finding thresholds of continuous variables.

Stereotactic LINAC radiosurgery for the treatment of typical intracranial meningiomas. Efficacy and safety after a follow-up of over 12 years

PURPOSE

The efficacy and safety of stereotactic radiosurgery (SRS) for treatment of intracranial meningiomas has been demonstrated in numerous studies with short- and intermediate-term follow-up. In this retrospective single-center study, we present long-term outcomes of SRS performed with a linear accelerator (LINAC) for typical intracranial meningiomas.

PATIENTS AND METHODS

Between August 1990 and December 2007, 148 patients with 168 typical intracranial meningiomas were treated with stereotactic LINAC-SRS, either as primary treatment or after microsurgical resection. A median tumor surface dose of 12 Gy (range 7-20 Gy) and a median maximum dose of 24.1 Gy (range 11.3-58.6 Gy) was applied. The median target volume was 4.7 ml (range 0.2-32.8 ml, SD ± 4.8 ml).

RESULTS

Overall mean radiological follow-up was 12.6 years. Tumor shrinkage was seen in 75 (44.6 %) and stable disease in 85 (50.6 %) cases. Eight of 168 meningiomas (4.8 %) showed local tumor progression. The tumor control rate (TCR) after 5, 10, and 15 years was 93.6 % at each time point, and the progression-free survival (PSF) rates were 92, 89, and 89 %, respectively. The neurological symptoms existing prior to LINAC-SRS improved in 77 patients (59.7 %), remained unchanged in 42 (32.6 %), and deteriorated in 10 (7.8 %) patients.

CONCLUSION

Our study emphasizes the efficacy of LINAC-SRS for de novo, residual and recurrent typical intracranial meningiomas. A high long-term local TCR with a low morbidity rate could be achieved. LINAC-SRS should thus be considered as a primary treatment option, as one arm of a combined treatment approach for incompletely resected meningiomas, or as a salvage therapy for recurrences.

Partial skull base tumour resection in combination with radiosurgery: an escape procedure or a reasonable solution of treatment?

Despite advancement in microsurgical techniques for skull base tumour surgery, approaches of this kind still represent a significant challenge for neurosurgeons due to the size of the tumour and its interference and proximity to important neural and vascular structures. After incomplete resection, gamma knife radiosurgery is becoming an alternative or adjunctive treatment option. In this article, some examples of our experience in combined treatment of the skull base tumours with surgical procedure and gamma knife therapy for the remaining tumour tissue are presented.