title: Impact of Adaptive Radiotherapy on Locally Advanced Head and Neck Cancer - A Dosimetric and Volumetric Study.
abstract: Objective of the study is to evaluate volumetric and dosimetric alterations taking place during radiotherapy for locally advanced head and neck cancer (LAHNC) and to assess benefit of replanning in them.
  
  
  METHODS
  Thirty patients with LAHNC fulfilling the inclusion and exclusion criteria were enrolled in a prospective study. Planning scans were acquired both pre-treatment and after 20 fractions (mid-course) of radiotherapy. Single plan (OPLAN) based on initial CT scan was generated and executed for entire treatment course. Beam configuration of OPLAN was applied to anatomy of interim scan and a hybrid plan (HPLAN30) was generated. Adaptive replanning (RPLAN30) for remaining fractions was done and dose distribution with and without replanning compared for remaining fractions.
  
  
  RESULTS
  Substantial shrinkage of target volume (TV) and parotids after 4 weeks of radiotherapy was reported (p<0.05). No significant difference between planned and delivered doses was seen for remaining fractions. Hybrid plans showed increase in delivered dose to spinal cord and parotids for remaining fractions. Interim replanning improved homogeneity of treatment plan and significantly reduced doses to cord (Dmax, D2% and D1%) and ipsilateral parotid (D33%, D50% and D66%) (p<0.05).
  
  
  CONCLUSIONS
  Use of one or two mid-treatment CT scans and replanning provides greater normal tissue sparing alongwith improved TV coverage.
authors.affiliation: Department of Radiotherapy, Rajiv Gandhi Cancer Institute and Research Centre, Delhi, India E-mail : abhinavdewan25@gmail.com.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Dewan
authors.forename: Sk
authors.initials: S
authors.lastname: Sharma
authors.forename: Ak
authors.initials: A
authors.lastname: Dewan
authors.forename: Himanshu
authors.initials: H
authors.lastname: Srivastava
authors.forename: Sheh
authors.initials: S
authors.lastname: Rawat
authors.forename: Anjali
authors.initials: A
authors.lastname: Kakria
authors.forename: Maninder
authors.initials: M
authors.lastname: Mishra
authors.forename: Suresh
authors.initials: S
authors.lastname: T
authors.forename: Krati
authors.initials: K
authors.lastname: Mehrotra
mesh_terms: D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000528:radiation effects; D011446:Prospective Studies; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D013116:Spinal Cord / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000379:methods