BREAST-CONSERVING RADIATION-THERAPY - POTENTIAL OF INVERSE PLANNING WITH INTENSITY MODULATION

PURPOSE: To evaluate inverse planning with beam-intensity modulation i n breast-conserving radiation therapy. MATERIALS AND METHODS: A protot ype inverse treatment-planning system was used in five patients with e arly-stage breast tumors: The prescription for the breast was 5,040 cG y in 180-cGy fractions, with the primary tumor site receiving 6,000 cG y in 214-cGy fractions. Isodose distributions from the prototype were compared section by section with those from conventional three-dimensi onal planning. RESULTS: The inverse planning system showed dose variat ion of 84%-98% to 111%-113% in the primary tumor site. For whole-breas t irradiation, 95% of the target volume received at least 4,000 cGy. H igh-dose areas were adjacent to the primary site. Lower-dose areas wer e in the most medial part of the breast. Compared with the conventiona l system, target doses were similar. The volume of lung and heart that received high doses was smaller; however, larger lung and heart volum es received doses of less than 1,200 cGy. CONCLUSION: Intensity modula tion may accomplish ''concomitant boost'' treatment. Acceptable dose g radients are achieved in the target volumes, with lower volumes of hig h-dose treatment in normal tissue. Plans that required comprehensive n odal radiation, in particular, were improved relative to conventional plans. Optimization of the planning system is needed to minimize the l ung and heart volumes that receive low-dose radiation.