title: Potential of adaptive radiotherapy to escalate the radiation dose in combined radiochemotherapy for locally advanced non-small cell lung cancer.
abstract: OBJECTIVE
  To evaluate the potential of adaptive radiotherapy (ART) for advanced-stage non-small cell lung cancer (NSCLC) in terms of lung sparing and dose escalation.
  
  
  METHODS
  In 13 patients with locally advanced NSCLC, weekly CT images were acquired during radio- (n=1) or radiochemotherapy (n=12) for simulation of ART. Three-dimensional (3D) conformal treatment plans were generated: conventionally fractionated doses of 66 Gy were prescribed to the planning target volume without elective lymph node irradiation (Plan_3D). Using a surface-based algorithm of deformable image registration, accumulated doses were calculated in the CT images acquired during the treatment course (Plan_4D). Field sizes were adapted to tumor shrinkage once in week 3 or 5 and twice in weeks 3 and 5.
  
  
  RESULTS
  A continuous tumor regression of 1.2% per day resulted in a residual gross tumor volume (GTV) of 49%±15% after six weeks of treatment. No systematic differences between Plan_3D and Plan_4D were observed regarding doses to the GTV, lung, and spinal cord. Plan adaptation to tumor shrinkage resulted in significantly decreased lung doses without compromising GTV coverage: single-plan adaptation in Week 3 or 5 and twice-plan adaptation in Weeks 3 and 5 reduced the mean lung dose by 5.0%±4.4%, 5.6%±2.9% and 7.9%±4.8%, respectively. This lung sparing with twice ART allowed an iso-mean lung dose escalation of the GTV dose from 66.8 Gy±0.8 Gy to 73.6 Gy±3.8 Gy.
  
  
  CONCLUSIONS
  Adaptation of radiotherapy to continuous tumor shrinkage during the treatment course reduced doses to the lung, allowed significant dose escalation and has the potential of increased local control.
authors: Department of Radiation Oncology, University of Wuerzburg, Wuerzburg, Germany. guckenberger_m@klinik.uni-wuerzburg.de
authors: Matthias
authors: M
authors: Guckenberger
authors: Juergen
authors: J
authors: Wilbert
authors: Anne
authors: A
authors: Richter
authors: Kurt
authors: K
authors: Baier
authors: Michael
authors: M
authors: Flentje
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy*; D002945:Cisplatin / Q000008:administration & dosage; D003131:Combined Modality Therapy / Q000379:methods; D019583:Dose Fractionation, Radiation; D005047:Etoposide / Q000008:administration & dosage; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy*; D008875:Middle Aged; D058958:Organs at Risk / Q000000981:diagnostic imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D012074:Remission Induction; D013116:Spinal Cord / Q000528:radiation effects; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden / Q000528:radiation effects; D014747:Vinblastine / Q000008:administration & dosage / Q000031:analogs & derivatives; D000077235:Vinorelbine
chemical_list: D014747:Vinblastine; D005047:Etoposide; D002945:Cisplatin; D000077235:Vinorelbine