title: Evaluating tumor response of non-small cell lung cancer patients with ¹⁸F-fludeoxyglucose positron emission tomography: potential for treatment individualization.
abstract: OBJECTIVE
  To assess early tumor responsiveness and the corresponding effective radiosensitivity for individual patients with non-small cell lung cancer (NSCLC) based on 2 successive (18)F-fludeoxyglucose positron emission tomography (FDG-PET) scans.
  
  
  METHODS
  Twenty-six NSCLC patients treated in Maastricht were included in the study. Fifteen patients underwent sequential chemoradiation therapy, and 11 patients received concomitant chemoradiation therapy. All patients were imaged with FDG before the start and during the second week of radiation therapy. The sequential images were analyzed in relation to the dose delivered until the second image. An operational quantity, effective radiosensitivity, αeff, was determined at the voxel level. Correlations were sought between the average αeff or the fraction of negative αeff values and the overall survival at 2 years. Separate analyses were performed for the primary gross target volume (GTV), the lymph node GTV, and the clinical target volumes (CTVs).
  
  
  RESULTS
  Patients receiving sequential treatment could be divided into responders and nonresponders, using a threshold for the average αeff of 0.003 Gy(-1) in the primary GTV, with a sensitivity of 75% and a specificity of 100% (P<.0001). Choosing the fraction of negative αeff as a criterion, the threshold 0.3 also had a sensitivity of 75% and a specificity of 100% (P<.0001). Good prognostic potential was maintained for patients receiving concurrent chemotherapy. For lymph node GTV, the correlation had low statistical significance. A cross-validation analysis confirmed the potential of the method.
  
  
  CONCLUSIONS
  Evaluation of the early response in NSCLC patients showed that it is feasible to determine a threshold value for effective radiosensitivity corresponding to good response. It also showed that a threshold value for the fraction of negative αeff could also be correlated with poor response. The proposed method, therefore, has potential to identify candidates for more aggressive strategies to increase the rate of local control and also avoid exposing to unnecessary aggressive therapies the majority of patients responding to standard treatment.
authors: Medical Radiation Physics, Stockholm University and Karolinska Institutet, Stockholm, Sweden. Electronic address: Iuliana.Livia.Dasu@ki.se.
authors: Iuliana
authors: I
authors: Toma-Dasu
authors: RaySearch Laboratories AB, Stockholm, Sweden.
authors: Johan
authors: J
authors: Uhrdin
authors: Medical Radiation Physics, Karolinska Institutet, Stockholm, Sweden.
authors: Marta
authors: M
authors: Lazzeroni
authors: Department of Radiation Oncology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors: Sara
authors: S
authors: Carvalho
authors: Department of Radiation Oncology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors: Wouter
authors: W
authors: van Elmpt
authors: Department of Radiation Oncology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors: Philippe
authors: P
authors: Lambin
authors: Department of Radiation Physics and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors: Alexandru
authors: A
authors: Dasu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D057285:Precision Medicine; D011379:Prognosis; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18