title: Predictive value of early 18F-FDG PET/CT studies for treatment response evaluation to ipilimumab in metastatic melanoma: preliminary results of an ongoing study.
abstract: OBJECTIVE
  Ipilimumab is a newly approved immunotherapeutic agent that has been shown to provide a survival benefit in patients with metastatic melanoma. (18)F-FDG PET/CT has demonstrated very satisfying results in detecting melanoma metastases in general. Using (18)F-FDG PET/CT we monitored patients with metastatic melanoma undergoing ipilimumab therapy during the course of treatment. The aim of our study was to evaluate the role of (18)F-FDG PET/CT performed after two cycles of ipilimumab in predicting the final response to therapy.
  
  
  METHODS
  In 22 patients suffering from unresectable metastatic melanoma, scheduled for ipilimumab treatment PET/CT scanning was performed before the start of treatment (baseline scan), after two cycles of treatment (early response) and at the end of treatment after four cycles (late response). Evaluation of the patient response to treatment on PET was based on the European Organization for Research and Treatment of Cancer 1999 criteria. Progression-free survival (PFS) and overall survival (OS) data are presented.
  
  
  RESULTS
  After the end of treatment, 15 patients were characterized as having progressive metabolic disease (PMD) and five as having stable metabolic disease (SMD), and two patients showed a partial metabolic response (PMR). Early PET/CT performed after two ipilimumab cycles predicted treatment response in 13 of the 15 PMD patients, in five of the five SMD patients and in neither of the two PMR patients. Both patients with PMR showed pseudoprogression after the second cycle and were therefore wrongly classified. According to the patients' clinical outcome, patients with late PMD had a median PFS of 3.6 months (mean 5.6 months), while patients with late SMD had a median PFS of 9.8 months (mean 9.0 months). In comparison, patients with early PMD had a median PFS of 2.7 months (mean 5.5 months) and patients with early SMD had a median PFS of 6.3 months (mean 7.5 months). The difference in PFS between the two groups was statistically significant for both early and late responses (log-rank p < 0.001). Median OS among patients with late PMD was 9.1 months (mean 11.2 months) and among those with late SMD 9.8 months (mean 10.7 months). The difference in OS between the two groups was statistically significant (log-rank p = 0.013). The median OS among patients with early PMD was 8.8 months (mean 12.0 months) and among those with early SMD 9.8 months (mean 10.0 months). The difference in OS between the two groups was statistically significant (log-rank p < 0.001).
  
  
  CONCLUSIONS
  (18)F-FDG PET/CT after two cycles of ipilimumab is highly predictive of the final treatment outcome in patients with PMD and SMD.
authors.affiliation: Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany, christos_saxpe@yahoo.gr.
authors.forename: Christos
authors.initials: C
authors.lastname: Sachpekidis
authors.forename: Lionel
authors.initials: L
authors.lastname: Larribere
authors.forename: Leyun
authors.initials: L
authors.lastname: Pan
authors.forename: Uwe
authors.initials: U
authors.lastname: Haberkorn
authors.forename: Antonia
authors.initials: A
authors.lastname: Dimitrakopoulou-Strauss
authors.forename: Jessica C
authors.initials: JC
authors.lastname: Hassel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D000074324:Ipilimumab; D008297:Male; D008545:Melanoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D000911:Antibodies, Monoclonal; D000074324:Ipilimumab; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18