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Local Control and Vertebral Compression Fracture Risk for a Novel Simultaneous Integrated Boost Technique in Stereotactic Spine Radiosurgery
E72
International Journal of Radiation Oncology Biology Physics
receiving low to intermediate dose results in more severe lymphopenia, even when accounting for GTV volume. This study validates the finding that brain V25 56% is associated with a higher risk of developing ASL. Further study should determine the impact of this constraint on overall treatment planning goals and organ-at-risk dosimetry. Author Disclosure: C. Dulaney: None. R.A. Popple: Research Grant; Varian. Honoraria; Varian. Travel Expenses; Varian. P. Warren: None. L.B. Nabors: None. M. Bredel: None. J.B. Fiveash: Research Grant; Varian Research Contract. Honoraria; Varian Research Contract. Travel Expenses; Varian Research Contract.
University of Texas MD Anderson Cancer Center, Houston, TX, 2University of Texas MD Anderson Cancer Center, Houston, TX, 3Dept. of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Dept. of Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX
2168 Local Control and Vertebral Compression Fracture Risk for a Novel Simultaneous Integrated Boost Technique in Stereotactic Spine Radiosurgery S.N. Elmore,1,2 T. Botticello,2 B. Winey,1,2 J.H. Shin,2 and K.S. Oh1,2; 1 Harvard Medical School, Boston, MA, 2Massachusetts General Hospital, Boston, MA Purpose/Objective(s): Spine stereotactic radiosurgery (SRS) to 24 Gy is associated with excellent local control, yet a vertebral compression fracture (VCF) risk as high as 40%. Intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) to gross tumor volumes (GTV) may retain local control while minimizing risk of VCF. We report clinical outcomes and dosimetric parameters for patients treated with spine SRS/SIB technique. Materials/Methods: Patients receiving SRS/SIB were retrospectively reviewed from a single institution. Clinical and dosimetric data were extracted from the medical record. Actuarial local control was determined per imaging or clinical documentation. Post-SRS VCF was defined as (a) radiographic loss of vertebral height or cortical disruption or (b) requirement of cement augmentation or surgical stabilization after SRS. Spine SRS was delivered using dynamic-MLC IMRT and planned on Raystation. Based on empiric clinical data, all plans were optimized with an equivalent uniform dose (EUD) constraint of < 20.5 Gy, with an a-value Z8. Results: Between April 2014 and January 2017, 30 patients with 31 unique sites were treated. Median follow-up was 9.4 months (IQR: 5.5-15.1) overall and 10.4 months (IQR 6.9-17.1) for surviving patients. Majority (58%) were male with a median age 66 years (IQR: 56-70) and median ECOG 0 (IQR: 0-1). Primary cancers were non-small cell lung cancer (19%), melanoma (16%), renal cell (10%), and thyroid (13%). Distribution was 7% cervical, 58% thoracic, 32% lumbar, and 3% overlapping spine sites. Median Spinal Instability Neoplastic Score was 5 (IQR 4-7). Most (65%) were asymptomatic, with 32% presenting with pain and 3% with weakness. Spinal surgery or cement augmentation was performed at 6% treated sites prior to SRS. Prescription doses were as follows: 81% received 18 Gy to PTV/24 Gy SIB to GTV, 16% received 18 Gy/22 Gy SIB, 3% to 16 Gy/22 Gy SIB. The median PTV was 80.6 cc (IQR: 55.1-101.4) with mean 85% coverage (SD 15%) by prescription dose. The median boost GTV was 6.6 cc (IQR: 2.6-10.1) with mean 72% coverage (SD 25%). Mean PTVestimated uniform dose (EUD) was 21.0 Gy (SD 1.1). Post-treatment fracture rate was 6% (NZ2) occurring at 9 and 15 months post-treatment with SINS 7 and 11. Crude and actuarial local control at 12 months were 97% and 100%, respectively. Conclusion: Spine SRS with SIB technique appears to maintain excellent local control while minimizing fracture risk in this small cohort of older patients with moderate spinal instability. Author Disclosure: S.N. Elmore: None. T. Botticello: None. B. Winey: Research Grant; Elekta. J.H. Shin: None. K.S. Oh: Research Grant; Elekta, Merck & Co., Inc.. Review and create questions for CME section of journal; IJROBP.
2169 Early Outcomes of a Novel Hypofractionated Dose Escalated Spine Simultaneous Integrated Boost Technique for Treatment of Metastatic Lesions Not Amenable to Spine Stereotactic Radiosurgery A. Farooqi,1 S. Narang,1 J. Li,1 A.J. Bishop,1 M.F. McAleer,2 C. Tatsui,3 L. Rhines,3 B. Amini,4 and A.J. Ghia1; 1Dept. of Radiation Oncology, The
Purpose/Objective(s): Traditional options for palliative management of spinal metastases include fractionated radiotherapy with or without surgery. However, patients with radioresistant disease respond poorly to conventionally fractionated treatment. Spine stereotactic radiosurgery (SSRS) delivers an ablative dose of radiation with high conformity to optimize tumor and pain control relative to standard fractionated RT. This technique is suboptimal for extended targets (i.e., >3 vertebral levels) owing to treatment alignment concerns which limit the ability to achieve stringent dose constraints on critical neural tissue. In these patients with radioresistant disease, we hypothesize that use of hypofractionated IMRT to dose escalate the GTV to 40 Gy as a spinal simultaneous integrated boost (SSIB) would allow for durable local control and palliation of symptoms. Materials/Methods: At a single institution, we retrospectively analyzed 10 patients with a combined 13 sites of spinal metastatic lesions who were treated using the SSIB technique from 2012-2016. The GTV and CTV were prescribed 40 Gy and 30 Gy, respectively, in 10 fractions using IMRT. The spinal cord was allowed a maximum point dose of 34 Gy. The GTV was identified as gross tumor seen on CT and MRI. The CTV encompassed the GTV, plus the involved vertebral bodies, at risk paraspinal space and spinal canal, followed by a PTV expansion of 3-5 mm. The median age for patients in our cohort was 55 years. 8 patients had a renal cell carcinoma primary, 1 had breast angiosarcoma, and 1 had hurthle cell thyroid carcinoma. Results: The median follow-up for patients in our cohort was 17.3 months. Of the 13 sites that were treated, only 1 showed in-field progression (7.7%), which occurred 4.5 months following treatment. Overall survival was 50%, with a median time to death following treatment of 9.4 months. There were no grade 2 or higher neurological toxicities reported for any of the patients. The mean dose to the GTV, CTV, and spinal cord was 41.56, 36.74, and 22.22 Gy respectively. The mean maximum dose to the spinal cord was 33.38 Gy. 7 of 10 patients had pain at presentation, of which 5 (71%) reported improvement and/or complete resolution of their pain following treatment. Conclusion: In the management of spinal metastatic disease that is not amenable to SSRS due to involvement of >3 contiguous vertebral body levels, dose escalation of the GTV to 40 Gy using a novel hypofractionated SSIB technique allowed for durable local and pain control in a small cohort of patients. This technique may allow for improved local control and palliation in patients with radioresistant disease, when compared to conventional 3D conformal standard fractionation RT. Author Disclosure: A. Farooqi: None. S. Narang: None. J. Li: Research Grant; BMS, Medtronic. Travel Expenses; Elekta. A.J. Bishop: None. M. McAleer: None. C. Tatsui: None. L. Rhines: None. B. Amini: None. A.J. Ghia: None.
2170 Does Immunotherapy Alter the Dose/Volume/ Outcome Relationship in the Normal Brain? D.V. Fried,1 O. Person,1 P. Mavroidis,2 B.S. Chera,1 T.M. Zagar,1 S.K. Das,1 M. Ewend,3 and L.B. Marks1; 1Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC, 2University of North Carolina at Chapel Hill, Chapel Hill, NC, 3 Department of Neurosurgery, University of North Carolina School of Medicine, Chapel Hill, NC Purpose/Objective(s): Stereotactic radiosurgery (SRS) is commonly used in patients with metastatic melanoma to the brain, resulting in favorable outcomes. Some studies have reported high rates of radiation necrosis in patients receiving SRS along with new systemic agents (e.g. immune checkpoint inhibitors, MAPK inhibitors). We performed a review of our experience using SRS in patients with melanoma brain metastases receiving immunotherapy. We hypothesize that immunotherapy may alter the effect of dose and volume metrics on rates of radiation necrosis.
International Journal of Radiation Oncology Biology Physics
receiving low to intermediate dose results in more severe lymphopenia, even when accounting for GTV volume. This study validates the finding that brain V25 56% is associated with a higher risk of developing ASL. Further study should determine the impact of this constraint on overall treatment planning goals and organ-at-risk dosimetry. Author Disclosure: C. Dulaney: None. R.A. Popple: Research Grant; Varian. Honoraria; Varian. Travel Expenses; Varian. P. Warren: None. L.B. Nabors: None. M. Bredel: None. J.B. Fiveash: Research Grant; Varian Research Contract. Honoraria; Varian Research Contract. Travel Expenses; Varian Research Contract.
University of Texas MD Anderson Cancer Center, Houston, TX, 2University of Texas MD Anderson Cancer Center, Houston, TX, 3Dept. of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Dept. of Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX
2168 Local Control and Vertebral Compression Fracture Risk for a Novel Simultaneous Integrated Boost Technique in Stereotactic Spine Radiosurgery S.N. Elmore,1,2 T. Botticello,2 B. Winey,1,2 J.H. Shin,2 and K.S. Oh1,2; 1 Harvard Medical School, Boston, MA, 2Massachusetts General Hospital, Boston, MA Purpose/Objective(s): Spine stereotactic radiosurgery (SRS) to 24 Gy is associated with excellent local control, yet a vertebral compression fracture (VCF) risk as high as 40%. Intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) to gross tumor volumes (GTV) may retain local control while minimizing risk of VCF. We report clinical outcomes and dosimetric parameters for patients treated with spine SRS/SIB technique. Materials/Methods: Patients receiving SRS/SIB were retrospectively reviewed from a single institution. Clinical and dosimetric data were extracted from the medical record. Actuarial local control was determined per imaging or clinical documentation. Post-SRS VCF was defined as (a) radiographic loss of vertebral height or cortical disruption or (b) requirement of cement augmentation or surgical stabilization after SRS. Spine SRS was delivered using dynamic-MLC IMRT and planned on Raystation. Based on empiric clinical data, all plans were optimized with an equivalent uniform dose (EUD) constraint of < 20.5 Gy, with an a-value Z8. Results: Between April 2014 and January 2017, 30 patients with 31 unique sites were treated. Median follow-up was 9.4 months (IQR: 5.5-15.1) overall and 10.4 months (IQR 6.9-17.1) for surviving patients. Majority (58%) were male with a median age 66 years (IQR: 56-70) and median ECOG 0 (IQR: 0-1). Primary cancers were non-small cell lung cancer (19%), melanoma (16%), renal cell (10%), and thyroid (13%). Distribution was 7% cervical, 58% thoracic, 32% lumbar, and 3% overlapping spine sites. Median Spinal Instability Neoplastic Score was 5 (IQR 4-7). Most (65%) were asymptomatic, with 32% presenting with pain and 3% with weakness. Spinal surgery or cement augmentation was performed at 6% treated sites prior to SRS. Prescription doses were as follows: 81% received 18 Gy to PTV/24 Gy SIB to GTV, 16% received 18 Gy/22 Gy SIB, 3% to 16 Gy/22 Gy SIB. The median PTV was 80.6 cc (IQR: 55.1-101.4) with mean 85% coverage (SD 15%) by prescription dose. The median boost GTV was 6.6 cc (IQR: 2.6-10.1) with mean 72% coverage (SD 25%). Mean PTVestimated uniform dose (EUD) was 21.0 Gy (SD 1.1). Post-treatment fracture rate was 6% (NZ2) occurring at 9 and 15 months post-treatment with SINS 7 and 11. Crude and actuarial local control at 12 months were 97% and 100%, respectively. Conclusion: Spine SRS with SIB technique appears to maintain excellent local control while minimizing fracture risk in this small cohort of older patients with moderate spinal instability. Author Disclosure: S.N. Elmore: None. T. Botticello: None. B. Winey: Research Grant; Elekta. J.H. Shin: None. K.S. Oh: Research Grant; Elekta, Merck & Co., Inc.. Review and create questions for CME section of journal; IJROBP.
2169 Early Outcomes of a Novel Hypofractionated Dose Escalated Spine Simultaneous Integrated Boost Technique for Treatment of Metastatic Lesions Not Amenable to Spine Stereotactic Radiosurgery A. Farooqi,1 S. Narang,1 J. Li,1 A.J. Bishop,1 M.F. McAleer,2 C. Tatsui,3 L. Rhines,3 B. Amini,4 and A.J. Ghia1; 1Dept. of Radiation Oncology, The
Purpose/Objective(s): Traditional options for palliative management of spinal metastases include fractionated radiotherapy with or without surgery. However, patients with radioresistant disease respond poorly to conventionally fractionated treatment. Spine stereotactic radiosurgery (SSRS) delivers an ablative dose of radiation with high conformity to optimize tumor and pain control relative to standard fractionated RT. This technique is suboptimal for extended targets (i.e., >3 vertebral levels) owing to treatment alignment concerns which limit the ability to achieve stringent dose constraints on critical neural tissue. In these patients with radioresistant disease, we hypothesize that use of hypofractionated IMRT to dose escalate the GTV to 40 Gy as a spinal simultaneous integrated boost (SSIB) would allow for durable local control and palliation of symptoms. Materials/Methods: At a single institution, we retrospectively analyzed 10 patients with a combined 13 sites of spinal metastatic lesions who were treated using the SSIB technique from 2012-2016. The GTV and CTV were prescribed 40 Gy and 30 Gy, respectively, in 10 fractions using IMRT. The spinal cord was allowed a maximum point dose of 34 Gy. The GTV was identified as gross tumor seen on CT and MRI. The CTV encompassed the GTV, plus the involved vertebral bodies, at risk paraspinal space and spinal canal, followed by a PTV expansion of 3-5 mm. The median age for patients in our cohort was 55 years. 8 patients had a renal cell carcinoma primary, 1 had breast angiosarcoma, and 1 had hurthle cell thyroid carcinoma. Results: The median follow-up for patients in our cohort was 17.3 months. Of the 13 sites that were treated, only 1 showed in-field progression (7.7%), which occurred 4.5 months following treatment. Overall survival was 50%, with a median time to death following treatment of 9.4 months. There were no grade 2 or higher neurological toxicities reported for any of the patients. The mean dose to the GTV, CTV, and spinal cord was 41.56, 36.74, and 22.22 Gy respectively. The mean maximum dose to the spinal cord was 33.38 Gy. 7 of 10 patients had pain at presentation, of which 5 (71%) reported improvement and/or complete resolution of their pain following treatment. Conclusion: In the management of spinal metastatic disease that is not amenable to SSRS due to involvement of >3 contiguous vertebral body levels, dose escalation of the GTV to 40 Gy using a novel hypofractionated SSIB technique allowed for durable local and pain control in a small cohort of patients. This technique may allow for improved local control and palliation in patients with radioresistant disease, when compared to conventional 3D conformal standard fractionation RT. Author Disclosure: A. Farooqi: None. S. Narang: None. J. Li: Research Grant; BMS, Medtronic. Travel Expenses; Elekta. A.J. Bishop: None. M. McAleer: None. C. Tatsui: None. L. Rhines: None. B. Amini: None. A.J. Ghia: None.
2170 Does Immunotherapy Alter the Dose/Volume/ Outcome Relationship in the Normal Brain? D.V. Fried,1 O. Person,1 P. Mavroidis,2 B.S. Chera,1 T.M. Zagar,1 S.K. Das,1 M. Ewend,3 and L.B. Marks1; 1Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC, 2University of North Carolina at Chapel Hill, Chapel Hill, NC, 3 Department of Neurosurgery, University of North Carolina School of Medicine, Chapel Hill, NC Purpose/Objective(s): Stereotactic radiosurgery (SRS) is commonly used in patients with metastatic melanoma to the brain, resulting in favorable outcomes. Some studies have reported high rates of radiation necrosis in patients receiving SRS along with new systemic agents (e.g. immune checkpoint inhibitors, MAPK inhibitors). We performed a review of our experience using SRS in patients with melanoma brain metastases receiving immunotherapy. We hypothesize that immunotherapy may alter the effect of dose and volume metrics on rates of radiation necrosis.