ESTRO 38 Abstract book

S629 ESTRO 38

E-posters Clinical

Electronic Poster: Clinical track: Head and Neck

EP-1133 SPECT-CT visualization of lymph flow pattern for radiotherapy planning in patients with tongue cance S. Novikov 1 , P. Krzhivitsky 2 , Z. Radzhabova 3 , M. Girshovitch 4 , M. Kotov 3 , O. Ponomareva 4 , R. Nazhmutdinov 3 , J. Melnik 4 , S. Kanaev 4 1 Prof. N.N. Petrov Research Institute of Oncology, Radiotherapy, St. Petersburg, Russian Federation ; 2 Prof. N.N. Petrov Research Institute of Oncology, Nuclear Medicine, St Petersburg, Russian Federation ; 3 Prof. N.N. Petrov Research Institute of Oncology, Head and Neck Surgery, St Petersburg, Russian Federation ; 4 Prof. N.N. Petrov Research Institute of Oncology, Radiotherapy, St Petersburg, Russian Federation Purpose or Objective to determine topography of sentinel and second echelon lymph nodes (LNs) in patients with tongue cancer and to analyze how this information can be used for radiotherapy planning. Material and Methods SPECT-CT visualization of lymph-flow patterns was performed in 26 primary patients with tongue cancer. Data acquisition was started 60-90 min after 4 peritumoral injections of 99mTc-nannocolloids (100- 150MBq in 0.3-0.4ml). On SPECT-CT images we determined topography of all sentinel and second echelon LNs according to standard LN levels and the type (mono- or bilateral) of lymph-flow from the primary tumour. All patients underwent MRI and US examinations of regional LNs and in 17 cases LNs status was verified by histological examination. Results In 14 of 26 (54%) patients SPECT-CT determined bilateral pattern of lymph flow from tongue cancer. In most of these patients (10 cases, 71%) distance from medial border of the primary lesions to medial sulcus of the tongue was less than 5 mm. On the contrary, in 10 of 12 patients with lateralized lesions (distance to medial sulcus 5 and more mm) we detected monolateral lymph-flow pattern. In 5 of 26 patients (19%) LNs with 99mTc-nannocolloids uptake were localized only on Ib-IIa levels. In another 16 cases (62%) sentinel and second echelon LNs were visualized on level Ib-IIa-III. Wide distribution (Level Ia-IIa- III-IV-VI) of LNs with tracer uptake was mentioned in 5 (19%) cases. One of 13 cT1-2N0M0 operated patients had non-signal LN metastasis on the same level with signal LN. None of the 2 non-operated cT1-2N0M0 patients demonstrated signs of LN recurrence. On the contrary, at least 2 of 9 patients with cT1-3N1M0 disease had metastatic LNs distally from LNs with uptake of radiocolloids. In 12 patients with monolateral lymph flow we didn’t find cases with contralateral LN involvement. According to proposed strategy of lymph flow guided radiotherapy we plan radiotherapy to regional LNs that localized on the same levels as visualized sentinel and second echelon LNs. Finally we compared standard treatment plans with radiation portals that were designed according to topography of sentinel and second echelon LNs. Preliminary data indicated that lymph flow guided strategy can significantly (1.6-3.3 times) reduce clinical treatment volume and absorbed dose in contralateral parotid gland (1.1-3.3 times). Conclusion In patients with tongue cancer and clinically negative regional lymph nodes SPECT-CT visualization of lymph flow from the primary tumour can significantly influence the

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