title: Predictive parameters in hypofractionated whole-breast 3D conformal radiotherapy according to the Ontario Canadian trial.
abstract: OBJECTIVE
  To evaluate the possible role of dosimetric parameters according Normal Tissue Complication Probability (NTCP) model as predictive of late toxicity and cosmesis in hypofractionated whole-breast three-dimensional conformal radiotherapy.
  
  
  METHODS
  A retrospective analysis on 215 consecutive early breast cancer patients treated with breast conserving surgery and adjuvant hypofractionated whole-breast radiotherapy (according the Ontario Canadian trial), with a 6 years median follow-up was conducted. To assess the impact of 10%-20% dose hotspots on different percent values of planning target volume (PTV) of the breast, we retrospectively employed the NTCP model of Lyman. PTV breast (PTVbr), V110 were identified. For statistical analysis theχ2and pairedt-test were used to find a correlation between late skin and subcutaneous toxicity and cosmetic outcome with dosimetrical parameters Multivariate analysis was performed with the aim to assess independently the impact of dosimetric and clinical parameters on late toxicity and cosmesis using Pearson's covariance.
  
  
  RESULTS
  Late skin toxicity was recorded in 47/215 (22%); and G3 toxicity occurred in 11 patients (5%). Cosmesis with excellent-good score was found in 172 patients (80%) while fair-poor score was found in 43 patients (20%). In univariateχ2analysis the V110 >10% of the PTV breast significantly correlated with higher toxicity (P<0.005, OR 9.60 [CI 3.89-23.72]). Cosmesis related to V110 >10% and PTV breast volume over 1,300 cc was significant at multivariate analysis (P<0.005, OR 6.07 [CI 2.36-15.59]).
  
  
  CONCLUSIONS
  To safely use one of the most important whole-breast hypofractionated radiotherapy schedules, we found some predictive paramaters on the basis of NTCP model by Lyman. These parameters may be useful in selection of elegible patients.
authors.affiliation: Radiation Oncology Unit.
authors.forename: Grazia
authors.initials: G
authors.lastname: Lazzari
authors.affiliation: Physics Department.
authors.forename: Angela
authors.initials: A
authors.lastname: Terlizzi
authors.affiliation: Medical Oncology Unit, Saint Giuseppe Moscati Hospital.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Della Vittoria Scarpati
authors.affiliation: Medical Oncology Unit, Saint Giuseppe Moscati Hospital.
authors.forename: Francesco
authors.initials: F
authors.lastname: Perri
authors.affiliation: Radiation Therapy Unit, Saints Giovanni Di Dio and Ruggi di Aragona, University of Salerno, Taranto, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: De Chiara
authors.affiliation: Radiation Oncology Unit.
authors.forename: Barbara
authors.initials: B
authors.lastname: Turi
authors.affiliation: Radiation Oncology Unit.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Silvano
keywords: NTCP model; Ontario Canadian Trial; PTV breast; V110; cosmesis; early breast cancer; hypofractionated radiotherapy; toxicity; whole-breast