Predictive parameters in hypofractionated whole-breast 3D conformal radiotherapy according to the Ontario Canadian trial

Grazia Lazzari,1 Angela Terlizzi,2 Giuseppina Della Vittoria Scarpati,3 Francesco Perri,3 Vincenzo De Chiara,4 Barbara Turi,1 Giovanni Silvano1 1Radiation Oncology Unit, 2Physics Department, 3Medical Oncology Unit, Saint Giuseppe Moscati Hospital, 4Radiation Therapy Unit, Saints Giovanni Di Dio and Ruggi di Aragona, University of Salerno, Taranto, Italy Aim: 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. Patients and 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 the χ2 and paired t-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 univariate χ2 analysis the V110 >10% of the PTV breast significantly correlated with higher toxicity (P10% and PTV breast volume over 1,300 cc was significant at multivariate analysis (P