Radiation therapy (RT) can promote anti-tumoral responses, but is also known to cause lymphatic endothelial cell apoptosis, loss of dermal lymphatics, and reduction in lymph transport to draining lymph node basins. When combined with lymph node dissection (LND), the radiogenic lymphatic disruption may possibly result in lymph stasis and dermal backflow. If not resolved, this disruption may lead to chronic inflammation, edema, fibrosis, adipose tissue deposition, and ultimately to functional deficits and disfigurement. Because the head and neck (HN) region contains 1/3 of the body’s lymph nodes, lymphatic responses to cancer progression and therapy may be significant. Furthermore, it may not be surprising that lymphedema has been estimated to impact as many as 75% of HN cancer survivors three months or more after LND and RT.
In this study, we used near-infrared fluorescence imaging to longitudinally assess the lymphatics of 18 patients undergoing treatment for cancer of the oral cavity, oropharynx, and/or larynx following intraoral and intradermal injections of ICG. Patients were imaged before and after surgery, before and after fractionated RT for up to 100 weeks after treatments. Patients who underwent both LND and RT developed lymphatic dermal backflow on treated sides ranging from days after the start of RT to weeks after its completion, while contralateral regions that were not associated with LND but also treated with RT, experienced no such changes in functional lymphatic anatomies. The results show for the first time, the striking reorganization of the lymphatic vasculature and may enable early diagnosis of HN lymphedema.