Internal mammarial lymph node radiotherapy in obese patients with breast cancer, at what expense?

The incidence of internal lymph node (imn)involvement was 4- 65% in breast cancer patients. despite studies indicatingthe positive effects of imnrt on the oncological results, most of the cliniciansavoided imnrt because of the toxicity related to the increased dose oforgans at risk (oar). we aimed to compare the dosimetric results of rt planswith and without imn containing planning target volumes (ptvs) using helicaltomotherapy (ht) in obese patients. materials and methods: the pmrt dataof 23 obese patients were evaluated retrospectively / dosimetrically. twoptvs with and without imn were defined and two separate plans were madewith ht. dose received by imn and oar were compared. results: theuntargeted imn v40 were calculated between 0% to 99%. when the plans areevaluated in terms of critical organs, the inclusion of the imn into the targetvolume, the most significant adverse effect was observed in heart doses inthe left chest wall (cw) irradiation. the significant increases in cardiac v5 (%62.6 vs %48.6 p=0.007), v10 (%38.2 vs %23.2 p=0.011), v20 (%14.15 vs %9.06p=0.045) and maximum heart dose (48.04 vs 43.2 p=0.043) were observed inthe left-side cw irradiations that involving the imn. in cw irradiation on theright side with imn, only a significant increase in mean heart dose (5.44 vs4.52 p=0.036) was observed. lung v5 doses were increased by inclusion withimn in both sides. there was no difference in the contralateral breast dosesin both plans for both sides. conclusions: if the imn is not targeted, some ofthe patients are getting appropriate doses in obese patients.