title: Intensity modulated proton beam radiation for brachytherapy in patients with cervical carcinoma.
abstract: OBJECTIVE
  To evaluate intensity modulated proton therapy (IMPT) in patients with cervical cancer in terms of coverage, conformity, and dose-volume histogram (DVH) parameters correlated with recommendations from magnetic resonance imaging (MRI)-guided brachytherapy.
  
  
  METHODS
  Eleven patients with histologically proven cervical cancer underwent primary chemoradiation for the pelvic lymph nodes, the uterus, the cervix, and the parametric region, with a symmetric margin of 1 cm. The prescription was for 50.4 Gy, with 1.8 Gy per fraction. The prescribed dose to the parametria was 2.12 Gy up to 59.36 Gy in 28 fractions as a simultaneous boost. For several reasons, the patients were unable to undergo brachytherapy. As an alternative, IMPT was planned with 5 fractions of 6 Gy to the cervix, including the macroscopic tumor with an MRI-guided target definition, with an isotropic margin of 5 mm for planning target volume (PTV) definition. Groupe-Europeen de Curietherapie and European society for Radiotherapy and Oncology (GEC-ESTRO) criteria were used for DVH evaluation. Reference comparison plans were optimized for volumetric modulated rapid arc (VMAT) therapy with the RapidArc (RA).
  
  
  RESULTS
  The dose to the high-risk volume was calculated with α/β = 10 with 89.6 Gy. For IMPT, the clinical target volume showed a mean dose of 38.2 ± 5.0 Gy (35.0 ±1.8 Gy for RA). The D98% was 31.9 ± 2.6 Gy (RA: 30.8 ± 1.0 Gy). With regard to the organs at risk, the 2Gy Equivalent Dose (EQD2) (α/β = 3) to 2 cm(3) of the rectal wall, sigmoid wall, and bladder wall was 62.2 ± 6.4 Gy, 57.8 ± 6.1 Gy, and 80.6 ± 8.7 Gy (for RA: 75.3 ± 6.1 Gy, 66.9 ± 6.9 Gy, and 89.0 ± 7.2 Gy, respectively). For the IMPT boost plans in combination with external beam radiation therapy, all DVH parameters correlated with <5% risk for grades 2 to 4 late gastrointestinal and genitourinary toxicity.
  
  
  CONCLUSIONS
  In patients who are not eligible for brachytherapy, IMPT as a boost technique additionally to external beam radiation therapy provides good target coverage and conformity and superior DVH parameters, compared with recommendations to MRI-guided brachytherapy. For selected patients, IMPT might be a valid alternative to brachytherapy and also superior to reference VMAT plans.
authors.affiliation: Oncology Institute of Southern Switzerland, Bellinzona, Switzerland.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Clivio
authors.forename: Anne
authors.initials: A
authors.lastname: Kluge
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
authors.forename: Christhardt
authors.initials: C
authors.lastname: Köhler
authors.forename: Oliver
authors.initials: O
authors.lastname: Neumann
authors.forename: Eugenio
authors.initials: E
authors.lastname: Vanetti
authors.forename: Waldemar
authors.initials: W
authors.lastname: Wlodarczyk
authors.forename: Simone
authors.initials: S
authors.lastname: Marnitz
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy; D000328:Adult; D000368:Aged; D001918:Brachytherapy; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy; D012809:Colon, Sigmoid / Q000528:radiation effects; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D061766:Proton Therapy / Q000379:methods*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*