The modified tangential irradiation technique for breast cancer: How to cover the entire axillary region

Purpose: The two-portal tangential irradiation technique has usually been a pplied to breast cancer patients after breast-conserving surgery (1, 2) and is expected to irradiate the axillary lymph node region to some extent (3) . We investigated the range of the axillary region covered by this techniqu e and tried to devise an optimal irradiation technique (modified tangential irradiation) that would cover the axillary lymph node region properly. Methods and Materials: We checked the status of the surgical clips left at axillary lymph node sites by reviewing the simulator films and planning CT scans of 63 patients who underwent axillary dissection of level I, I-II, or I-III lymph nodes. Then we created the modified tangential irradiation tec hnique and applied this technique to 16 patients and checked the irradiatio n volume by CT scans. Results: We found that all of the surgical clips on lateral-view simulator films were on the ventral side of the dorsal edge line of the humeral head. All but one clip were on the caudal side of the caudal edge line of the hu meral head. Accordingly, it is possible to irradiate almost all axillary ly mph node regions by setting the dorsal edge of the irradiation field on lat eral-view simulator films at the dorsal edge of the humeral head and the cr anial edge at the caudal edge of the humeral head. Conclusions: All breast tissue and the entire axillary lymph node region ca n be covered by the modified tangential irradiation technique without incre asing the lung volume irradiated. (C) 2000 Elsevier Science Inc.