Central Nervous System

PV QA 2 - Poster Viewing Q&A 2

MO_11_2735 - Efficacy and Safety of Hypofractionated Stereotactic Radiosurgery for Perioptic Lesions

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Efficacy and Safety of Hypofractionated Stereotactic Radiosurgery for Perioptic Lesions
H. Speckter1, I. Miches1, J. Bido1, G. Hernandez1, D. Rivera1, L. Suazo1, S. Valenzuela1, J. M. Garcia2, and P. Stoeter1; 1CEDIMAT, Santo Domingo, Dominican Republic, 2Centro Gamma Knife Dominicano, Santo Domingo, Dominican Republic

Purpose/Objective(s): Treatment of lesions in close proximity to the optic pathways remains challenging with either conventional resection or with stereotactic radiosurgery (SRS). Hypofractionation has been considered as an alternate treatment. A benefit of hypofractionation for perioptic lesions can be expected because of the low alpha/beta ratio of the optic pathway of 1.11 Gy [submitted to ASTRO 2018].

Materials/Methods: Between 2011 and 2017 a total of 54 patients with perioptic lesions (27 pituitary adenomas, 16 meningiomas, 7 craniopharyngiomas, 1 cavernoma, 1 AVM, 1 metastasis and 1 sarcoma) were treated with hypofractionation (4 treatments with 5 session with mean margin dose to lesion 5x6.75 Gy, 45 treatments with 4 sessions: 4x5.34 Gy, and 5 treatments with 3 sessions: 3x6.20 Gy) at our Gamma Knife center. Mean age was 46y [11-78y], mean lesion volume was 10.26cc [0.42-40.82cc] Treatments were performed with the stereotactic frame left on during the whole treatment period. All treatments concluded satisfactorily and were well tolerated. Spatial frame displacement was measured <0.3mm using CT images. Exact delineation of the optic pathways was performed on high resolution 3D T1 images and additionally since 2016 by applying FGATIR sequences [submitted to ASTRO 2018] using a 3 Tesla scanner. Dose Volume Histograms were elaborated separately for chiasm, both optic nerves and tracts.

Results: After a mean imaging follow up period of 22 months [4-64m], local control was achieved in all but 1 lesion (craniopharyngioma), 12 lesions stayed stable. An overall mean reduction in volume of 2.30% per month was observed (pituitary adenomas: mean reduction 3.13%/m, meningiomas: mean reduction 1.09%/m). Mean maximum optic dose for the 3 fractionation schedules was 5x6.15Gy, 4x5.84Gy, 3x7.42Gy. Mean follow up period for vision evaluation was 19 months [5-53m]. Improved vision was observed in 10 cases, worsened vision in 2 cases: 1 caused by increased tumor volume, 1 case was confirmed for RION (maximum point chiasm dose 4x6.4Gy, optic tracts received up to 4x6.3Gy and 4x6.2Gy, respectively).

Conclusion: According to our preliminary results, hypofractionated SRS can be considered as an efficient and relatively safe alternate for the treatment of lesions in close proximity of the optic pathways. Additionally to the benefit of the steep dose gradient in stereotactic radiosurgery, hypofractionation permits an even more aggressive treatment of lesions close to the visual system, profiting from its low alpha/beta ratio.

Author Disclosure: H. Speckter: IGKRF; IGKRF. I. Miches: None. J. Bido: None. G. Hernandez: None. L. Suazo: None. S. Valenzuela: None. J.M. Garcia: None. P. Stoeter: None.

Herwin Speckter, MS

Biography:
Herwin Speckter serves as medical physicist at the Dominican Gamma Knife Center since its opening in 2011 and as medical physicist at the medical center CEDIMAT since its opening in 1999, in Santo Domingo, Dominican Republic.

Herwin Speckter studied physics at the Johannes Gutenberg University in Mainz, Germany. He developed his thesis in high field magnetic resonance spectroscopy of brain and breast cancer at the Max Planck Institute for Polymer Research in Mainz, Germany.

Between 1992 and 1998, before moving to the Dominican Republic, he was faculty member of the departments of Nuclear Medicine and as well Neuroradiology at the University Hospital in Mainz.

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