title: A novel two-step optimization method for tandem and ovoid high-dose-rate brachytherapy treatment for locally advanced cervical cancer.
abstract: OBJECTIVE
  To present a novel method allowing fast volumetric optimization of tandem and ovoid high-dose-rate treatments and to quantify its benefits.
  
  
  METHODS
  Twenty-seven CT-based treatment plans from 6 consecutive cervical cancer patients treated with four to five intracavitary tandem and ovoid insertions were used. Initial single-step optimized plans were manually optimized, approved, and delivered plans created with a goal to cover high-risk clinical target volume (HR-CTV) with D90 >90% and minimize rectum, bladder, and sigmoid D2cc. For the two-step optimized (TSO) plan, each single-step optimized plan was replanned adding a structure created from prescription isodose line to the existent physician delineated HR-CTV, rectum, bladder, and sigmoid. New, more rigorous dose-volume histogram constraints for the critical organs at risks (OARs) were used for the optimization. HR-CTV D90 and OAR D2ccs were evaluated in both plans.
  
  
  RESULTS
  TSO plans had consistently smaller D2ccs for all three OARs while preserving HR-CTV D90. On plans with "excellent" CTV coverage, average D90 of 96% (91-102%), sigmoid, bladder, and rectum D2cc, respectively, reduced on average by 37% (16-73%), 28% (20-47%), and 27% (15-45%). Similar reductions were obtained on plans with "good" coverage, average D90 of 93% (90-99%). For plans with "inferior" coverage, average D90 of 81%, the coverage increased to 87% with concurrent D2cc reductions of 31%, 18%, and 11% for sigmoid, bladder, and rectum, respectively.
  
  
  CONCLUSIONS
  The TSO can be added with minimal planning time increase but with the potential of dramatic and systematic reductions in OAR D2ccs and in some cases with concurrent increase in target dose coverage. These single-fraction modifications would be magnified over the course of four to five intracavitary insertions and may have real clinical implications in terms of decreasing both acute and late toxicities.
authors.affiliation: Department of Radiation Oncology, School of Medicine, Virginia Commonwealth University, Richmond, VA.
authors.forename: Manju
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Department of Radiation Oncology, School of Medicine, Virginia Commonwealth University, Richmond, VA.
authors.forename: Emma C
authors.initials: EC
authors.lastname: Fields
authors.affiliation: Department of Radiation Oncology, School of Medicine, Virginia Commonwealth University, Richmond, VA. Electronic address: adtodor@vcu.edu.
authors.forename: Dorin A
authors.initials: DA
authors.lastname: Todor
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D012809:Colon, Sigmoid / Q000528:radiation effects; D005260:Female; D006801:Humans; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*
keywords: Cervical Cancer; HDR Brachytherapy; Tandem and ovoid; Volume optimization