Improvement of radiotherapy planning in breast cancer by internal mammary lymphoscintigraphy

Abstract

In breast cancer treatment, parasternal radiation with standard fields does not allow for the individual anatomical variability of the internal mammary lymph nodes (IMN). One possibility for individual treatment planning taking into account the depth and lateral extension of the IMN is to visualise this node chain by internal mammary lymphoscintigraphy (IMLS) prior to radiation. Using a modified IMLS technique, the anatomical distribution pattern of the IMN was assessed. IMN showed a marked individual variation in location, with an average depth of 2.8 cm (range: 1–6.8 cm). According to these data a “standard” parasternal field with a reference depth of 3 cm would not allow for adequate coverage of the lymph nodes in 36.1% of cases. Using a reference depth of 4 cm, 12.1% of cases would still be untreated. The IMN's distance from the midline ranged from 0 to 6.5 cm with an average value of 2.7 cm. Their exact localisation on the simulation film allows for individual shaping of the parasternal field, thus ensuring adequate enclosure of the IMN and matching of the field margins. As IMLS is easy to perform with standard equipment and was found to be a reliable method, we recommend IMLS as an effective aid in treatment planning in the radiation therapy of breast cancer.