Miscellaneous Posters PO101

Abstract

Purpose Controversy exists regarding radiotherapy of patients with connective tissue disorders due to increased radiosensitivity. GammaTile® (GT Medical Technologies, Tempe, Arizona) is a novel brachytherapy strategy for intracranial radiotherapy. The suspension of the seeds in this matrix results in more uniformed dose delivery throughout the periphery of resection cavities, potentially reducing necrosis risk and conserving surrounding brain parenchyma. We hypothesized that GammaTile® would result in decreased dose to the scalp and incision wound in a patient with a Grade 3 glioma and limited scleroderma with active disease in the overlying scalp. Materials and Methods Preoperative MRI was used to estimate the number of tiles needed to deliver 60 Gy to a 5mm depth from the resection cavity. The tiles were placed after a right frontotemporal craniotomy with maximal safe resection. Day 1 post-implant dosimetry was performed with MRI and CT utilizing MIM to contour the sources and planning target volume (PTV); a 5mm expansion from the surgical cavity along tumor involved surfaces. A hypothetical standard external beam (EBRT) plan was generated in Eclipse with a 1cm expansion from the cavity and a 5mm expansion to PTV. A similar volume to GammaTile was generated using the CybrerKnife planning system with a 5 mm expansion of the cavity to PTV. Both plans were dosed to 59.3 Gy in 33 fractions to 95% coverage. All dose clouds were imported into Velocity and converted to equivalent dose in 2Gy (EQD2). Organs at risk (OARs) including the scalp and incision scar were contoured and dose volume histograms (DHVs) generated in Velocity. The patient underwent physical exam at 1, 3, and 6 months and MRI brain at 3 and 6 months, with photo documentation of the scalp. Results A total of 10 tiles were ordered and ultimately used with no tiles split to cover a 39.76 cc resection cavity as indicated on Day 1 post implant imaging. The resulting PTV was 31.18 cc with the V100% (60 Gy) of 99% and D90 of 118.7%. Compared to the GammaTile dose cloud, those generated by both EBRT plans resulted in greater irradiation to the surgical scar (Figure 1A-C, green line). Figure 1D-F shows the DVH between GammaTile (green), standard EBRT (red) and CybrerKnife (blue) for the scar, scalp and normal brain parenchyma. Overall, there was significant reduction in dose to these OARs with GammaTile. In particular, the maximum dose delivered to the scar and scalp by GammaTile was reduced to half of that from other external beam techniques (∼25-30 Gy vs ∼55 Gy). MRI imaging at 3 and 6 months lacked evidence of disease recurrence or radionecrosis. At the 6 month follow up visit, the surgical scar was well healed and there were no skin changes to the surrounding scalp at any time during follow up. Conclusions Compared to EBRT techniques, GammaTile brachytherapy is able to deliver considerably less dose to the scalp and scar incision in a Grade 3 glioma patient with limited scleroderma and active disease in the overlying scalp. The patient did not have any of the expected acute toxicities that would be seen with EBRT to the scalp or have issues with incision healing. This report demonstrates the dosimetric and clinical benefit of GammaTile irradiation for patients with intracranial neoplasms and limited scleroderma and should be considered for similar patients with connective tissue disease. Controversy exists regarding radiotherapy of patients with connective tissue disorders due to increased radiosensitivity. GammaTile® (GT Medical Technologies, Tempe, Arizona) is a novel brachytherapy strategy for intracranial radiotherapy. The suspension of the seeds in this matrix results in more uniformed dose delivery throughout the periphery of resection cavities, potentially reducing necrosis risk and conserving surrounding brain parenchyma. We hypothesized that GammaTile® would result in decreased dose to the scalp and incision wound in a patient with a Grade 3 glioma and limited scleroderma with active disease in the overlying scalp. Preoperative MRI was used to estimate the number of tiles needed to deliver 60 Gy to a 5mm depth from the resection cavity. The tiles were placed after a right frontotemporal craniotomy with maximal safe resection. Day 1 post-implant dosimetry was performed with MRI and CT utilizing MIM to contour the sources and planning target volume (PTV); a 5mm expansion from the surgical cavity along tumor involved surfaces. A hypothetical standard external beam (EBRT) plan was generated in Eclipse with a 1cm expansion from the cavity and a 5mm expansion to PTV. A similar volume to GammaTile was generated using the CybrerKnife planning system with a 5 mm expansion of the cavity to PTV. Both plans were dosed to 59.3 Gy in 33 fractions to 95% coverage. All dose clouds were imported into Velocity and converted to equivalent dose in 2Gy (EQD2). Organs at risk (OARs) including the scalp and incision scar were contoured and dose volume histograms (DHVs) generated in Velocity. The patient underwent physical exam at 1, 3, and 6 months and MRI brain at 3 and 6 months, with photo documentation of the scalp. A total of 10 tiles were ordered and ultimately used with no tiles split to cover a 39.76 cc resection cavity as indicated on Day 1 post implant imaging. The resulting PTV was 31.18 cc with the V100% (60 Gy) of 99% and D90 of 118.7%. Compared to the GammaTile dose cloud, those generated by both EBRT plans resulted in greater irradiation to the surgical scar (Figure 1A-C, green line). Figure 1D-F shows the DVH between GammaTile (green), standard EBRT (red) and CybrerKnife (blue) for the scar, scalp and normal brain parenchyma. Overall, there was significant reduction in dose to these OARs with GammaTile. In particular, the maximum dose delivered to the scar and scalp by GammaTile was reduced to half of that from other external beam techniques (∼25-30 Gy vs ∼55 Gy). MRI imaging at 3 and 6 months lacked evidence of disease recurrence or radionecrosis. At the 6 month follow up visit, the surgical scar was well healed and there were no skin changes to the surrounding scalp at any time during follow up. Compared to EBRT techniques, GammaTile brachytherapy is able to deliver considerably less dose to the scalp and scar incision in a Grade 3 glioma patient with limited scleroderma and active disease in the overlying scalp. The patient did not have any of the expected acute toxicities that would be seen with EBRT to the scalp or have issues with incision healing. This report demonstrates the dosimetric and clinical benefit of GammaTile irradiation for patients with intracranial neoplasms and limited scleroderma and should be considered for similar patients with connective tissue disease.