Five-field IMRT class solutions and dosimetric planning guidelines for implementing accelerated partial breast irradiation.

PURPOSE: A comprehensive set of planning guidelines was developed to aid in achieving reproducible dosimetric results for external beam accelerated partial breast irradiation (APBI). The methodology for the development of class solutions for dosimetric planning of the APBI technique, including dose constraint recommendations, is presented for target coverage and conformity as well as normal tissues.

METHODS AND MATERIALS: A conservative patient setup was simulated on a linear accelerator, and a comprehensive arrangement of gantry and couch angles was measured for clearance. This provided the foundation for available beam arrangements to develop reproducible and conformal 5-field intensity modulated radiation therapy partial breast plans. Forty patients were planned. Patient plans were assessed according to anatomy specific features, such as laterality and seroma location within the breast.

RESULTS: Clearance tables are presented to give permissible gantry and couch orientations according to measurements facilitated by patient simulation. Beam arrangement class solutions are presented for left- and right-sided APBI patients. Dosimetric recommendations are made based on the results of 40 patient plans. The median and range, describing target coverage and target conformity, are reported, as are normal tissue constraints for ipsilateral lung, ipsilateral breast, heart, liver, and contralateral breast. In all cases, the dose recommendations were at least as strict as multi-institutional APBI trials. In the case of ipsilateral lung and ipsilateral breast, the planning recommendations are more stringent.

CONCLUSIONS: APBI using a 5-field intensity modulated radiation therapy technique was comprehensively developed and evaluated to provide recommendations yielding highly conformal and reproducible treatment plans. This provides a clear method to implement external beam APBI planning and delivery.