The Effectiveness and Factors Related to Treatment Results of Gamma Knife Radiosurgery for Meningiomas

Abstract

A retrospective analysis was conducted on 80 patients with intracranial mengiomas treated with Gamma Knife radiosurgery between 1993 and 1996. The purpose was to analyze the efficacy of the treatment and to assess appropriate treatment parameters. The results were assessed by regular MR examinations, and tumor volume was measured at 6-month intervals. Mean follow-up duration was 21 months (range 6–45 months). 63 meningiomas were at the skull base and 17 were distal from the skull base. Tumor volumes <5 ml (n=38), 5–10 ml (n=21), 10–15 ml (n=14), 15–20 ml (n=7). The patients were divided into 3 groups according to the radiation dose. The groups were high-dose (peripheral dose 17–20 Gy, n=19), medium-dose (15–16 Gy, n=33) and low-dose (12–14 Gy, n=28) groups. A statistical method (Generalized Estimation Equation) was applied to compare treatment results in these groups with different doses and tumor volumes. The volume measurement at the latest follow-up showed 74% (59/80) meningiomas decreased in volume, 17% (14/80) had no tumor enlargement and 9% (7/80) had increased in volume. The increased volume was found more frequently in the patients with a short (6–12 months) follow-up period. In this series, the tumors had 32% reduction in average tumor volume at 3 years after radiosurgery. At the range of 12–20 Gy peripheral dose (PD), radiosurgery was effective to reduce tumor volume 0.7% per month (p<0.05). However, higher doses had no significant difference on tumor volume reduction (p>0.05). On the other hand, high-dose (PD>17 Gy) treatment was associated with a higher risk of temporary tumor swelling and the development of adverse radiation effects (AREs). The AREs detected on MR images occurred in (25/80) 31% patients. Only 6/25 AREs were symptomatic and 2 had neurological sequelae. Peripheral doses, tumor volumes and their locations had significant impacts on the ARE (p<0.05). In conclusion, a peripheral dose of 15–16 Gy may be adequate for meningiomas with small volumes (<5 ml). In larger tumors (>10 ml) a lower PD is preferred (12–14 Gy). To avoid initial tumor swelling and ARE, high-dose irradiation (PD>17 Gy) is not recommended for meningiomas larger than 5 ml.

Gamma Knife Radiosurgery for Glomus Jugulare and Tympanicum

“…However, significant tumor volume reduction was observed in the MRI follow-up at the 12th month. This finding is consistent with those for other benign tumors (e.g., meningioma or neuroma) after radiosurgery, although it occurs less frequently [35,36] . We believe that such initial volume enlargement is due to transient tumor swelling after treatment, and it usually will regress spontaneously by the 12-month follow-up.…”

Dose-Volume Effect in Gamma Knife Radiosurgery of Meningiomas

“…4.5 ml), the prescribed dose may vary from 17 to 20 Gy, for middle volumes (4.5-10 ml) the prescribed dose ranges from 14 to 17 Gy, and for large volumes (10-42.28 ml) the prescribed dose ranges from 12 to 14 Gy. Clinical observation about dose prescription around the 3% isoeffect line approximates to the recommendations of Kondziolka, and Nakamula, and the dose selection from the mathematical model is similar to Pan et al [7,8,17,18].…”

“…After calculation for risk probability by an integrated logistic formula, we found all 4 cases to exceed the 3% isoeffect line. Pan et al [17] published 80 cases with meningiomas treated by the Leksell Gamma Knife in 1998. After analyzing the adverse radiation effect on follow-up MR scans, the authors believed that volume and radiation dose were significantly related to the development of adverse radiation effect after gamma knife surgery; high radiation (peripheral dose 117 Gy) should be avoided for tumor volumes larger than 5 ml, the peripheral dose of 15-16 Gy might be adequate for small volume (!5 ml), but for a large volume (110 ml) a low dose was preferable (12)(13)(14).…”

Gamma knife radiosurgery for lymphoplasmacyte-rich meningioma

“…Comparing with other radiotherapy, GKS preferentially spared normal tissue from radiation injury. In our series in 1998 [3], the tumor volume, location and radiation dose were all significantly related to the development of ARE. Therefore, peripheral dose of 15-16 Gy for tumor volume less than 5 ml and 12-14 Gy for tumors larger than 10 ml were suggested.…”

“…The tumor volume in this case was 16.83 ml before GKS and 5.73 ml after 21 months follow-up. The tumor reduction of the patient was up to 66%, and it was much higher than that of our other meningioma patients (post GKS: average 32% reduction by 3 years follow-up) [3] (Fig. 3).…”