title: Can errors in reconstructing pre-chemotherapy target volumes contribute to the inferiority of sequential chemoradiation in stage III non-small cell lung cancer (NSCLC)?
abstract: Concurrent chemo-radiotherapy (CT-RT) has been shown to be superior to sequential CT-RT for stage III non-small cell lung cancer (NSCLC). Pre-chemotherapy gross tumor volumes (GTV) are commonly contoured for sequential CT-RT and, as significant inter-clinician variability exists in defining GTV's for lung cancer, we postulated that the poorer local control observed with sequential CT-RT may partly be due to the larger errors in defining GTV after chemotherapy-induced tumor regression. Pre-and post-chemotherapy CT scans for RT planning (RTP) were performed in ten patients who received induction chemotherapy for NSCLC. Image registration of pre- and post-chemotherapy RTP scans was performed for all patients. GTV's were first contoured in the conventional manner by two clinicians, i.e. by visual reconstruction from hard copies of the pre-chemotherapy diagnostic CT scans ('GTV-visual'). A 'GTV-match' was then contoured after image-registration, and the 'gold standard' volume was considered to be the overlap of the 'GTV-match' generated by both clinicians. The 'GTV-match' was on average 31-40% larger than 'GTV-visual'. The mean percentage of the 'gold standard', which was not covered by the 'GTV-visual' was similar for both clinicians, i.e. 26.3+/-12.5 and 28.0+/-15.0%. The inter-clinician agreement in contouring improved after image registration. These data suggest that conventional visual contouring of pre-chemotherapy GTV's may fail to treat the actual pre-chemotherapy tumor volume, and thus confound studies evaluating optimal sequencing of chemo-radiotherapy in NSCLC.
authors.affiliation: Department of Radiation Oncology, Erasmus Medical Center Rotterdam, Groene Hilledijk 301, Rotterdam 3075 EA, The Netherlands.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Lagerwaard
authors.forename: Paul J M
authors.initials: PJ
authors.lastname: van de Vaart
authors.forename: Peter W J
authors.initials: PW
authors.lastname: Voet
authors.forename: Margriet R J
authors.initials: MR
authors.lastname: Nijssen-Visser
authors.forename: Regine H
authors.initials: RH
authors.lastname: Schuchhard-Schipper
authors.forename: Hans P J
authors.initials: HP
authors.lastname: Joosten
authors.forename: Swie Swat
authors.initials: SS
authors.lastname: Oei
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D003287:Contrast Media; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media