title: Patterns of Recurrence in Electively Irradiated Lymph Node Regions After Definitive Accelerated Intensity Modulated Radiation Therapy for Head and Neck Squamous Cell Carcinoma.
abstract: OBJECTIVE
  To provide a comprehensive risk assessment on the patterns of recurrence in electively irradiated lymph node regions after definitive radiation therapy for head and neck cancer.
  
  
  METHODS
  Two hundred sixty-four patients with stage cT2-4N0-2M0 squamous cell carcinoma of the oropharynx, larynx, or hypopharynx treated with accelerated intensity modulated radiation therapy between 2008 and 2012 were included. On the radiation therapy planning computed tomography (CT) scans from all patients, 1166 lymph nodes (short-axis diameter ≥5 mm) localized in the elective volume were identified and delineated. The exact sites of regional recurrences were reconstructed and projected on the initial radiation therapy planning CT scan by performing coregistration with diagnostic imaging of the recurrence.
  
  
  RESULTS
  The actuarial rate of recurrence in electively irradiated lymph node regions at 2 years was 5.1% (95% confidence interval 2.4%-7.8%). Volumetric analysis showed an increased risk of recurrence with increasing nodal volume. Receiver operating characteristic analysis demonstrated that the summed long- and short-axis diameter is a good alternative for laborious volume calculations, using ≥17 mm as cut-off (hazard ratio 17.8; 95% confidence interval 5.7-55.1; P<.001).
  
  
  CONCLUSIONS
  An important risk factor was identified that can help clinicians in the pretreatment risk assessment of borderline-sized lymph nodes. Not overtly pathologic nodes with a summed diameter ≥17 mm may require a higher than elective radiation therapy dose. For low-risk elective regions (all nodes <17 mm), the safety of dose de-escalation below the traditional 45 to 50 Gy should be investigated.
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. Electronic address: sven.vandenbosch@radboudumc.nl.
authors.forename: Sven
authors.initials: S
authors.lastname: van den Bosch
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Dijkema
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Lia C G
authors.initials: LC
authors.lastname: Verhoef
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Zwijnenburg
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Geert O
authors.initials: GO
authors.lastname: Janssens
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Johannes H A M
authors.initials: JH
authors.lastname: Kaanders
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D016001:Confidence Intervals; D005260:Female; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007012:Hypopharyngeal Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D007822:Laryngeal Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D008198:Lymph Nodes / Q000473:pathology / Q000528:radiation effects*; D015182:Lymphatic Irradiation; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D009959:Oropharyngeal Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D018570:Risk Assessment; D047368:Tumor Burden