Computerized body tomography in breast cancer. I. Internal mammary nodes and radiation treatment planning

Abstract

The internal mammary area has been reviewed on CBT scans from 46 postmastectomy patients, and chest wall thicknesses computed there from the scan. Thicknesses ranged from 10 to 43 mm and 16 to 70 mm on the operated and nonoperated sides, and were weight-related in 38 modified mastectomy patients. Direct Cobalt and 15 MeV electron portals delivered 97-98% of the dose prescribed at 3 cm to a depth of 35 mm, the maximum average thickness on the operated side, while 12 and 10 MeV electrons gave 10 and 20% less at that depth. At 70 mm, underdosage with Cobalt and 15 MeV was 22% and 72%; insignificant doses were delivered with 10 and 12 MeV electrons. Routine determination of chest wall thickness is recommended in patients planned for electron beam treatment, in obese patients, and in patients treated with tangential photon techniques, to avoid underdosage to the internal mammary area. Internal mammary nodes were not routinely visualized, but abnormalities consistent with enlarged nodes were seen in six patients and gross recurrence in another.

Radiation therapy for operable breast cancer

“…By 1979, Munzenrider et al described the use of a new modality, computed tomography, to assess the location and depth of the IMNs to improve radiation planning and dose coverage. 72 In addition, electron beam irradiation could now cover the IMN chain at the required greater depths; this would be critical for reducing high doses to the pericardium, myocardium, and coronary vessels that were usually given with cobalt and direct photon radiation.…”

Imaging techniques in breast cancer

“…Attempts to improve the accuracy of preoperative axillary staging by axillary views at the time of mammography are inaccurate, and ultrasonography does not have the ability to detect lymph node metastases reliably. The internal mammary nodes have been evaluated by CT [27], which has shown abnormalities consistent with lymphadenopathy in the anterior mediastinum but does not visualize the internal mammary lymph nodes when they are of normal size.…”