title: Pathological characteristics of spine metastases treated with high-dose single-fraction stereotactic radiosurgery.
abstract: OBJECTIVE Spine radiosurgery is increasingly being used to treat spinal metastases. As patients are living longer because of the increasing efficacy of systemic agents, appropriate follow-up and posttreatment management for these patients is critical. Tumor progression after spine radiosurgery is rare; however, vertebral compression fractures are recognized as a more common posttreatment effect. The use of radiographic imaging alone posttreatment may makeit difficult to distinguish tumor progression from postradiation changes such as fibrosis. This is the largest series from a prospective database in which the authors examine histopathology of samples obtained from patients who underwent surgical intervention for presumed tumor progression or mechanical pain secondary to compression fracture. The majority of patients had tumor ablation and resulting fibrosis rather than tumor progression. The aim of this study was to evaluate tumor histopathology and characteristics of patients who underwent pathological sampling because of radiographic tumor progression, fibrosis, or collapsed vertebrae after receiving high-dose single-fraction stereotactic radiosurgery. METHODS Between January 2005 and January 2014, a total of 582 patients were treated with linear accelerator-based single-fraction (18-24 Gy) stereotactic radiosurgery. The authors retrospectively identified 30 patients (5.1%) who underwent surgical intervention for 32 lesions with vertebral cement augmentation for either mechanical pain or instability secondary to vertebral compression fracture (n = 17) or instrumentation (n = 15) for radiographic tumor progression. Radiation and surgical treatment, histopathology, and long-term outcomes were reviewed. Survival and time to recurrence were calculated using the Kaplan-Meier method. RESULTS The mean age at the time of radiosurgery was 59 years (range 36-80 years). The initial pathological diagnoses were obtained for all patients and primarily included radioresistant tumor types, including renal cell carcinoma in 7 (22%), melanoma in 6 (19%), lung carcinoma in 4 (12%), and sarcoma in 3 (9%). The median time to surgical intervention was 24.7 months (range 1.6-50.8 months). The median follow-up and overall survival for all patients were 42.5 months and 41 months (overall survival range 7-86 months), respectively. The majority of assessed lesions showed no evidence of tumor on pathological review (25 of 32, 78%), while a minority of lesions revealed residual tumor (7 of 32, 22%). The median survival for patients after tumor recurrence was 5 months (range 2-70 months). CONCLUSIONS High-dose single-fraction radiosurgery is tumor ablative in the majority of instances. In a minority of cases, tumor persists and salvage treatments should be considered.
authors.affiliation: Departments of1Radiation Oncology.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Katsoulakis
authors.affiliation: 4Neurosurgery, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Ilya
authors.initials: I
authors.lastname: Laufer
authors.affiliation: 4Neurosurgery, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Mark
authors.initials: M
authors.lastname: Bilsky
authors.affiliation: 2Pathology.
authors.forename: Narasimhan P
authors.initials: NP
authors.lastname: Agaram
authors.affiliation: 3Medical Physics, and.
authors.forename: Michael
authors.initials: M
authors.lastname: Lovelock
authors.affiliation: Departments of1Radiation Oncology.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D058498:Kyphoplasty / Q000379:methods; D008297:Male; D008545:Melanoma / Q000601:surgery; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D012189:Retrospective Studies; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery; D013123:Spinal Fusion / Q000379:methods; D013125:Spinal Neoplasms / Q000150:complications / Q000473:pathology* / Q000601:surgery*; D016896:Treatment Outcome
keywords: IMRT = intensity-modulated radiation therapy; PTV = planning target volume; SRS = stereotactic radiosurgery; SUV = standardized uptake value; VCF = vertebral compression fracture; image-guided radiation therapy; pathological correlation; radiation fibrosis; spine stereotactic radiosurgery; tumor ablation