title: Response and long-term control of bone metastases after peptide receptor radionuclide therapy with (177)Lu-octreotate.
abstract: Peptide receptor radionuclide therapy (PRRT) is an efficient treatment for gastroenteropancreatic neuroendocrine tumors (GEP NETs), with outstanding overall response rates and survival. However, little is known about the particular efficacy regarding bone metastasis (BM).
  
  
  METHODS
  We retrospectively analyzed a consecutive subgroup of 42 patients with BM of GEP NETs treated with PRRT ((177)Lu-octreotate, 4 intended cycles at 3 monthly intervals [10-14 wk]; mean activity per cycle, 8.1 GBq). Availability of restaging and outcome data was required for patient inclusion. Baseline characteristics, including age, tumor origin, performance score, Ki-67 index, tumor load, tumor uptake, plasma chromogranin A, and neuron-specific enolase, were analyzed regarding impact on tumor regression (modified M.D. Anderson criteria) and time to progression. Survival analyses were performed using Kaplan-Meier curves, log-rank test at a significance level of P less than 0.05, and Cox proportional hazards model for uni- and multivariate analyses.
  
  
  RESULTS
  Median follow-up was 32 mo. The observed response of BMs consisted of complete remission in 2 (4.8%), partial remission in 14 (33.3%), minor response in 5 (11.9%), stable disease in 16 (38.1%), and progressive disease in 5 (11.9%) patients. Median progression-free survival and overall survival (OS) were 35 mo (26-44, 95% confidence interval) and 51 mo (37-65, 95% confidence interval), respectively. Patients with responding BMs (complete remission, partial remission, or minor response) exhibited a trend toward better OS (median OS not reached after 53 mo) when compared to nonresponding patients (39 mo, P = 0.076). Only Ki-67 index (>10%) and chromogranin A level (>600 ng/mL) contributed to regression analysis.
  
  
  CONCLUSIONS
  BM of GEP NETs is effectively controlled by PRRT, with long progression-free survival and OS. Poor patient condition and multifocality of BMs do not clearly affect treatment efficacy, possibly encouraging the use of PRRT in advanced bone metastatic disease. Larger studies are needed to assess predictors of treatment outcome in these patients.
authors.affiliation: Department of Nuclear Medicine, University Hospital, Bonn, Germany. samer.ezziddin@ukb.uni-bonn.de
authors.forename: Samer
authors.initials: S
authors.lastname: Ezziddin
authors.forename: Amir
authors.initials: A
authors.lastname: Sabet
authors.forename: Florian
authors.initials: F
authors.lastname: Heinemann
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: Yong-Hing
authors.forename: Hojjat
authors.initials: H
authors.lastname: Ahmadzadehfar
authors.forename: Stefan
authors.initials: S
authors.lastname: Guhlke
authors.forename: Tobias
authors.initials: T
authors.lastname: Höller
authors.forename: Winfried
authors.initials: W
authors.lastname: Willinek
authors.forename: Christian
authors.initials: C
authors.lastname: Boy
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Biersack
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000556:secondary*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008495:Medical Oncology / Q000379:methods; D008875:Middle Aged; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000473:pathology / Q000532:radiotherapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011868:Radioisotopes / Q000627:therapeutic use*; D018000:Receptors, Peptide / Q000737:chemistry*; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: C554548:177Lu-octreotate; D011868:Radioisotopes; D018000:Receptors, Peptide; D015282:Octreotide