Abstract
Purpose:This study was to investigate the dosimetric benefit of a novel intensity modulated radiation therapy (IMRT) technique for irradiating the left breast and regional lymph node (RLN).Methods:The breast and RLN (internal mammary node and periclavicular node) and normal tissue were contoured for 16 consecutive left‐sided breast cancer patients previously treated with RT after lumpectomy. Nine equi‐spaced fields IMRT (9 ‐field IMRT), tangential multi‐beam IMRT (tangential‐IMRT) and IMRT with fixed‐jaw technique (FJT‐IMRT) were developed and compared with three‐dimensional conformal RT (3DCRT). Prescribed dose was 50 Gy in 25 fractions. Dose distributions and dose volume histograms were used to evaluate plans.Results:All IMRTs achieved similar target coverage and substantially reduced heart V30 and V20 compared to the 3DCRT. The average heart mean dose had different changes, which were 9.0Gy for 9‐field IMRT, 5.7Gy for tangential‐IMRT and 4.2Gy for FJT‐IMRT. For the contralateral lung and breast, the 9‐field IMRT has the highest mean dose; and the FJT‐IMRT and tangential‐IMRT had similar lower value. For the thyroid, both 9‐field IMRT and FJT‐IMRT had similar V30 (20% and 22%) and were significantly lower than that of 3DCRT (34%) and tangential‐IMRT (46%). Moreover, the thyroid mean dose of FJT‐IMRT is the lowest. For cervical esophagus and humeral head, the FJT‐IMRT also had the best sparing.Conclusion:All 9‐field IMRT, tangential‐IMRT and FJT‐IMRT had superiority for targets coverage and substantially reduced the heart volume of high dose irradiation. The FJT‐IMRT showed advantages of avoiding the contralateral breast and lung irradiation and decreasing the thyroid, humeral head and cervical esophagus radiation dose at the expense of a slight monitor units (MUs) increasing.
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