Prone hypofractionated whole-breast radiotherapy without a boost to the tumor bed: comparable toxicity of IMRT versus a 3D conformal technique.

PURPOSE: We report a comparison of the dosimetry and toxicity of three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT) among patients treated in the prone position with the same fractionation and target of the hypofractionation arm of the Canadian/Whelan trial. METHODS AND MATERIALS: An institutional review board-approved protocol identified a consecutive series of early-stage breast cancer patients treated according to the Canadian hypofractionation regimen but in the prone position. Patients underwent IMRT treatment planning and treatment if the insurance carrier approved reimbursement for IMRT; in case of refusal, a 3D-CRT plan was used. A comparison of the dosimetric and toxicity outcomes during the acute, subacute, and long-term follow-up of the two treatment groups is reported. RESULTS: We included 97 consecutive patients with 100 treatment plans in this study (3 patients with bilateral breast cancer); 40 patients were treated with 3D-CRT and 57 with IMRT. IMRT significantly reduced the maximum dose (Dmax median, 109.96% for 3D-CRT vs. 107.28% for IMRT; p < 0.0001, Wilcoxon test) and improved median dose homogeneity (median, 1.15 for 3D-CRT vs. 1.05 for IMRT; p < 0.0001, Wilcoxon test) when compared with 3D-CRT. Acute toxicity consisted primarily of Grade 1 to 2 dermatitis and occurred in 92% of patients. Grade 2 dermatitis occurred in 13% of patients in the 3D-CRT group and 2% in the IMRT group. IMRT moderately decreased rates of acute pruritus (p = 0.03, chi-square test) and Grade 2 to 3 subacute hyperpigmentation (p = 0.01, Fisher exact test). With a minimum of 6 months' follow-up, the treatment was similarly well tolerated in either group, including among women with large breast volumes. CONCLUSION: Hypofractionated breast radiotherapy is well tolerated when treating patients in the prone position, even among those with large breast volumes. Breast IMRT significantly improves dosimetry but yields only a modest but confirmed benefit in terms of toxicities. If a concurrent boost to the tumor bed is not required, a conformal 3D-CRT approach can adequately deliver prone whole-breast hypofractionation radiotherapy.

Phase I-II trial of prone accelerated intensity modulated radiation therapy to the breast to optimally spare normal tissue.

PURPOSE: To report the clinical feasibility of a trial of accelerated whole-breast intensity modulated radiotherapy, with the patient in prone position, optimally to spare the heart and lung. PATIENTS AND METHODS: Patients with stages I or II breast cancer, excised by breast conserving surgery with negative margins, were eligible for this institutional review board-approved prospective trial. Computed tomography simulation was performed with the patient prone on a dedicated breast board, in the exact position used for treatment. A dose of 40.5 Gy, delivered at 2.7 Gy in 15 fractions, was prescribed to the index breast with an additional concomitant boost of 0.5 Gy delivered to the tumor bed, for a total dose of 48 Gy to the lumpectomy site. Physics constraints consisted of limiting 5% of the heart volume to receive > or = 18 Gy and < or = 10% of the ipsilateral lung volume to receive > or = 20 Gy. RESULTS: Between September 2003 and August 2005, 91 patients were enrolled on the study. Median length of follow-up was 12 months (range, 1 to 28 months). In all patients the technique was feasible and heart and lung sparing was achieved as prescribed by the protocol. Acute toxicities consisting mostly of reversible grades 1-2 skin dermatitis (67%) and fatigue (18%) occurred in 75 patients. One patient sustained a regional recurrence rapidly followed by distant metastases. CONCLUSION: Accelerated whole breast intensity modulated radiotherapy in the prone position is feasible and it permits a drastic reduction in the volume of lung and heart tissue exposed to significant radiation.