A practical and easy method to locate the first three internal mammary lymph node-bearing areas

Purpose: To assess the distance from a clinically recognized anatomic landm ark to the different costocondral interspaces in female patients to facilit ate the design of radiation fields intended to include specific internal ma mmary nodal areas. Methods and Materials: The distance from the suprasternal notch (SSN) to th e caudal portion of the first through fourth interspace was measured on a c omputer display of the chest skeleton of 65 female patients,vith left-sided breast cancer. The relationship between these distances and bone size (ste rnal length and standing height) was assessed via linear regression. In 21 of the 65 patients where myocardial perfusion imaging of the heart was avai lable, the relationship between the location of the 3rd costochondral inter space and the left ventricle was assessed. Results: In 90% of patients (59/65), the first, second, third, and fourth i nterspace were within 5, 8.5, 11, and 14 cm of the SSN, respectively. The S SN-interspace distances did not correlate well with sternal length (r = 0.2 8) or standing height (r = 0.31). In 20 of 21 patients (95%), the third int erspace "shadowed" the cephalad aspect of the left heart ventricle. Median "shadowing" was 3 cm (range 0.5-6 cm). Conclusion: The caudal portion of the third costochondral interspace is les s than or equal to 11 cm caudal to the SSN in 90% of patients. These measur ements can be used to clinically design radiation therapy fields intended t o treat the upper three interspaces. The distance from the SSN to the 1st t hrough 4th interspaces is not related to sternal length or to standing heig ht. In patients with left-sided breast cancer, radiation treatment fields d esigned to include the internal mammary lymph nodes in the upper three inte rspaces may incidentally include a portion of the heart. (C) 2001 Elsevier Science Inc.