title: Bone density as a marker for local response to radiotherapy of spinal bone metastases in women with breast cancer: a retrospective analysis.
abstract: BACKGROUND
  We designed this study to quantify the effects of radiotherapy (RT) on bone density as a local response in spinal bone metastases of women with breast cancer and, secondly, to establish bone density as an accurate and reproducible marker for assessment of local response to RT in spinal bone metastases.
  
  
  METHODS
  We retrospectively assessed 135 osteolytic spinal metastases in 115 women with metastatic breast cancer treated at our department between January 2000 and January 2012. Primary endpoint was to compare bone density in the bone metastases before, 3 months after and 6 months after RT. Bone density was measured in Hounsfield units (HU) in computed tomography scans. We calculated mean values in HU and the standard deviation (SD) as a measurement of bone density before, 3 months and 6 months after RT. T-test was used for statistical analysis of difference in bone density as well as for univariate analysis of prognostic factors for difference in bone density 3 and 6 months after RT.
  
  
  RESULTS
  Mean bone density was 194.8 HU ± SD 123.0 at baseline. Bone density increased significantly by a mean of 145.8 HU ± SD 139.4 after 3 months (p = .0001) and by 250.3 HU ± SD 147.1 after 6 months (p < .0001). Women receiving bisphosphonates showed a tendency towards higher increase in bone density in the metastases after 3 months (152.6 HU ± SD 141.9 vs. 76.0 HU ± SD 86.1; p = .069) and pathological fractures before RT were associated with a significantly higher increase in bone density after 3 months (202.3 HU ± SD 161.9 vs. 130.3 HU ± SD 129.2; p = .013). Concomitant chemotherapy (ChT) or endocrine therapy (ET), hormone receptor status, performance score, applied overall RT dose and prescription of a surgical corset did not correlate with a difference in bone density after RT.
  
  
  CONCLUSIONS
  Bone density measurement in HU is a practicable and reproducible method for assessment of local RT response in osteolytic metastases in breast cancer. Our analysis demonstrated an excellent local response within metastases after palliative RT.
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. robert.foerster@med.uni-heidelberg.de.
authors.forename: Robert
authors.initials: R
authors.lastname: Foerster
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. christian.eisele@med.uni-heidelberg.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Eisele
authors.affiliation: Department of Medical Biometry, University Hospital Heidelberg, Im Neuenheimer Feld 305, 69120, Heidelberg, Germany. bruckner@imbi.uni-heidelberg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bruckner
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. tilmann.bostel@med.uni-heidelberg.de.
authors.forename: Tilman
authors.initials: T
authors.lastname: Bostel
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. ingmar.schlampp@med.uni-heidelberg.de.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Schlampp
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. robert.wolf@med.uni-heidelberg.de.
authors.forename: Robert
authors.initials: R
authors.lastname: Wolf
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. juergen.debus@med.uni-heidelberg.de.
authors.forename: Juergen
authors.initials: J
authors.lastname: Debus
authors.affiliation: Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. harald.rief@med.uni-heidelberg.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Rief
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D015519:Bone Density / Q000528:radiation effects*; D001859:Bone Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000532:radiotherapy; D018275:Carcinoma, Lobular / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D014057:Tomography, X-Ray Computed
chemical_list: D014408:Biomarkers, Tumor