Factors Influencing Freedom From Progression Of Meningiomas Treated With Gamma Knife RadiosurgeryKeywords: gamma knife, outcome, meningioma, Imaging, radiosurgeryInteractive Manuscript
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What is the background behind your study?
What is the purpose of your study?
To evaluate the impact of tumor grade, volume, and dose on freedom from progression (FFP) of meningiomas treated with Gamma Knife radiosurgery (GKRS) upfront, for recurrence after prior surgery alone, or for recurrence after prior radiotherapy.
Describe your patient group.
All meningioma patients treated at UCSF with GKRS 1991-2007 were retrospectively reviewed.
Describe what you did.
Actuarial FFP by patient and by lesion was estimated from the date of GKRS using the Kaplan-Meier method. Log-rank tests and univariate and multivariate Cox proportional hazards analyses were performed.
Describe your main findings.
283 patients and 459 tumors were analyzed, including 376 tumors treated at the first or only GKRS session and 83 additional tumors treated with subsequent sessions. By lesion, the median dose was 15 Gy (range, 10-20 Gy) and median target volume 2.6 ml (0.1-35.0 ml). FFP was equivalent for benign meningiomas and tumors with no tissue diagnosis, so they were combined as “benign”; 135 of 142 patients treated with GKRS upfront and 68 of 82 patients treated for recurrence after surgery had “benign” tumors, with 5-year FFP probabilities of 93% and 91%, respectively. Among patients treated for recurrence after radiotherapy, 2-year FFP probabilities were 74% for 19 “benign”, 50% for 10 atypical, and 36% for 29 malignant meningioma patients. Analyzed by tumor, 2- and 5-year FFP probabilities were 99% and 95% for 202 “benign” tumors treated upfront and 93% and 89% for 94 “benign” meningiomas treated for recurrence after surgery alone. Among the tumors treated for recurrence after radiotherapy, 2-year FFP probabilities were 75% for 23 “benign”, 54% for 24 atypical, and 60% for 61 malignant meningiomas. Grade was not necessarily reassessed at recurrence. Aside from treatment timing, the most important prognostic variable for FFP was target volume (by quartile). There was no evidence for a dose-FFP relationship in the range of ~12-18 Gy for any subset.
Describe the main limitation of this study.
This is a retrospective study.
Describe your main conclusion.
No evidence was found for a dose-FFP relationship. GKRS provided excellent FFP for small- to medium-sized low-grade meningiomas treated upfront or for recurrence after surgery.
Describe the importance of your findings and how they can be used by others.
Other strategies are needed to improve results for higher grade meningiomas and for any meningioma that has recurred after previous radiotherapy.
To evaluate the impact of tumor grade, volume, and dose on freedom from progression (FFP) of meningiomas treated with Gamma Knife radiosurgery (GKRS) upfront, for recurrence after prior surgery alone, or for recurrence after prior radiotherapy.
All meningioma patients treated at UCSF with GKRS 1991-2007 were retrospectively reviewed.
Actuarial FFP by patient and by lesion was estimated from the date of GKRS using the Kaplan-Meier method. Log-rank tests and univariate and multivariate Cox proportional hazards analyses were performed.
283 patients and 459 tumors were analyzed, including 376 tumors treated at the first or only GKRS session and 83 additional tumors treated with subsequent sessions. By lesion, the median dose was 15 Gy (range, 10-20 Gy) and median target volume 2.6 ml (0.1-35.0 ml). FFP was equivalent for benign meningiomas and tumors with no tissue diagnosis, so they were combined as “benign”; 135 of 142 patients treated with GKRS upfront and 68 of 82 patients treated for recurrence after surgery had “benign” tumors, with 5-year FFP probabilities of 93% and 91%, respectively. Among patients treated for recurrence after radiotherapy, 2-year FFP probabilities were 74% for 19 “benign”, 50% for 10 atypical, and 36% for 29 malignant meningioma patients. Analyzed by tumor, 2- and 5-year FFP probabilities were 99% and 95% for 202 “benign” tumors treated upfront and 93% and 89% for 94 “benign” meningiomas treated for recurrence after surgery alone. Among the tumors treated for recurrence after radiotherapy, 2-year FFP probabilities were 75% for 23 “benign”, 54% for 24 atypical, and 60% for 61 malignant meningiomas. Grade was not necessarily reassessed at recurrence. Aside from treatment timing, the most important prognostic variable for FFP was target volume (by quartile). There was no evidence for a dose-FFP relationship in the range of ~12-18 Gy for any subset.
This is a retrospective study.
No evidence was found for a dose-FFP relationship. GKRS provided excellent FFP for small- to medium-sized low-grade meningiomas treated upfront or for recurrence after surgery.
Other strategies are needed to improve results for higher grade meningiomas and for any meningioma that has recurred after previous radiotherapy.
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