title: A phase II comparative study of gross tumor volume definition with or without PET/CT fusion in dosimetric planning for non-small-cell lung cancer (NSCLC): primary analysis of Radiation Therapy Oncology Group (RTOG) 0515.
abstract: BACKGROUND
  Radiation Therapy Oncology Group (RTOG) 0515 is a Phase II prospective trial designed to quantify the impact of positron emission tomography (PET)/computed tomography (CT) compared with CT alone on radiation treatment plans (RTPs) and to determine the rate of elective nodal failure for PET/CT-derived volumes.
  
  
  METHODS
  Each enrolled patient underwent definitive radiation therapy for non-small-cell lung cancer (≥ 60 Gy) and had two RTP datasets generated: gross tumor volume (GTV) derived with CT alone and with PET/CT. Patients received treatment using the PET/CT-derived plan. The primary end point, the impact of PET/CT fusion on treatment plans was measured by differences of the following variables for each patient: GTV, number of involved nodes, nodal station, mean lung dose (MLD), volume of lung exceeding 20 Gy (V20), and mean esophageal dose (MED). Regional failure rate was a secondary end point. The nonparametric Wilcoxon matched-pairs signed-ranks test was used with Bonferroni adjustment for an overall significance level of 0.05.
  
  
  RESULTS
  RTOG 0515 accrued 52 patients, 47 of whom are evaluable. The follow-up time for all patients is 12.9 months (2.7-22.2). Tumor staging was as follows: II = 6%; IIIA = 40%; and IIIB = 54%. The GTV was statistically significantly smaller for PET/CT-derived volumes (98.7 vs. 86.2 mL; p < 0.0001). MLDs for PET/CT plans were slightly lower (19 vs. 17.8 Gy; p = 0.06). There was no significant difference in the number of involved nodes (2.1 vs. 2.4), V20 (32% vs. 30.8%), or MED (28.7 vs. 27.1 Gy). Nodal contours were altered by PET/CT for 51% of patients. One patient (2%) has developed an elective nodal failure.
  
  
  CONCLUSIONS
  PET/CT-derived tumor volumes were smaller than those derived by CT alone. PET/CT changed nodal GTV contours in 51% of patients. The elective nodal failure rate for GTVs derived by PET/CT is quite low, supporting the RTOG standard of limiting the target volume to the primary tumor and involved nodes.
authors.affiliation: Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Bradley
authors.forename: Kyounghwa
authors.initials: K
authors.lastname: Bae
authors.forename: Noah
authors.initials: N
authors.lastname: Choi
authors.forename: Ken
authors.initials: K
authors.lastname: Forster
authors.forename: Barry A
authors.initials: BA
authors.lastname: Siegel
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Brunetti
authors.forename: James
authors.initials: J
authors.lastname: Purdy
authors.forename: Sergio
authors.initials: S
authors.lastname: Faria
authors.forename: Toni
authors.initials: T
authors.lastname: Vu
authors.forename: Wade
authors.initials: W
authors.lastname: Thorstad
authors.forename: Hak
authors.initials: H
authors.lastname: Choy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy / Q000556:secondary; D004947:Esophagus / Q000528:radiation effects; D005260:Female; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D058958:Organs at Risk / Q000528:radiation effects; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden