A semi-automatic planning technique for whole breast irradiation with tangential IMRT fields

Abstract

Purpose: To implement a semi-automatic planning technique for whole breast irradiation with two tangential IMRT fields and to test the produced dose distribution against clinical 3DCRT plans, for introducing the technique in clinical practice.

Methods: The Auto-Planning module of the Pinnacle³ (Philips) treatment planning system was used for generating a Treatment Technique on left-sided breast cancer patients treated in free breathing or in deep inspiration breath hold (DIBH) and to right-sided breast cancer patients. The technique was evaluated against 3DCRT clinical plans in terms of dosimetric plan parameters. Plan robustness toward patient displacements was assessed on a subset of patients by inducing shifts to the isocenter.

Results: A statistically significant improvement in target coverage and dose homogeneity was observed for autoIMRT. No statistically significant differences were observed for ipsilateral organs, except for the ipsilateral lung in left DIBH, where slightly lower D_mean and V_18% are registered for autoIMRT. Slightly higher D_mean doses (although far below the constraints) to contralateral organs were observed for autoIMRT plans. AutoIMRT plans were shown to be as robust as 3DCRT plans toward isocenter shifts, with a maximum decrease in CTV coverage of -2.2% and -2.1% for autoIMRT and 3DCRT, respectively. Average planning times were 40 min for 3DCRT and 6 min for IMRT plans.

Conclusions: The developed autoIMRT technique was proven to be advantageous for target coverage and homogeneity and sufficiently robust towards isocenter displacements. The use of automated planning consistently reduces the planning workload with improvements in plan quality.

Keywords: Automated planning; Breast cancer; IMRT; Radiotherapy; Whole breast irradiation.