ESTRO 2020 Abstract book

S484 ESTRO 2020

99mTc-radiocolloids. SLN biopsy with the subsequent obligatory standard LN dissection were performed 8-12 hours after mapping. Results SPECT-CT visualized at least one SLN in 26 of 27 evaluated patents. Bilateral lymph flow from the tongue cancer was detected in 10 (38.4%), monolateral – in another 16 (61.6%) patients. In 5 (19.2%) of 26 evaluated patients SLN were localized only on Ib-IIa levels. In 4 of these 5 observations lymph flow had monolateral pattern. In 53.8% cases (14 patients) SPECT-CT visualized SLN on the I-IIa-III levels. In 2 of 14 cases lymph flow was bilateral. In remaining 7 patients SLN had widespread topography (Ib-IIa-III-IV-V levels) with bilateral lymph-flow. In 16 patients with monolateral lymph flow there was no case of contralateral LN involvement or contralateral LN recurrence. Among evaluated 26 patients, metastases in SLN were detected in 6 cases. In 3 cases metastases were revealed in SLN. Additional non-sentinel lymph nodes were diagnosed in 2 patients and in all cases they were localized on the same levels as SLN. In 2 patients with non involved SLN examination of LN removed by standard lymphatic dissection identified LN metastases that were localized at the same levels as SLN. In one patient SLN and other nodes obtained after standard monolateral LN dissection were free of metastases but during follow-up we diagnosed metastases in SLN localized in contralateral IIa SLN which was not removed during primary treatment. Conclusion In patients with monolateral lymph flow our data advocate irradiation of only ipsilateral regional lymph nodes. Irradiation of LN that localized on the same levels as SLN can be considered as necessary and sufficient. This concept must be validated in prospective trials. PO-0810 Prognostic value of lymph node-to-primary tumor standardized uptake value ratio in NPC T. Hung 1 , J.T. Chang 1 , C. Lin 1 1 Chang Gung Memorial Hospital, Radiation Oncology, Taoyuan, Taiwan Purpose or Objective To investigate the prognostic value of the relative maximum standardized uptake value (SUV) ratio between neck lymph node and primary tumor (SUV-N / SUV-T) measured by pretreatment [18F]-FDG PET in patients with nasopharyngeal carcinoma (NPC). Material and Methods We retrospectively reviewed patients with non- disseminated NPC who underwent PET scan before radical intensity-modulated radiotherapy (IMRT). PET-derived metabolic variables such as maximum SUV of the primary tumor (SUV-T) and neck lymph nodes (SUV-N), and the lymph node-to-primary tumor SUV (SUV-N / SUV-T) ratio were assessed. Receiver operating characteristic analysis was performed to identify the optimal cut-off value for SUV-N / SUV-T ratio. The prognostic value of SUV-N / SUV- T on distant metastasis-free survival (DMFS) was evaluated using Kaplan-Meier method and log-rank test for univariate analysis and Cox proportional hazard model for multivariate analysis. Results In the 437 eligible patients, the median follow-up was 62.9 months (range, 2.1–113.0). Patients with low SUV-N / SUV- T (≤ 0.9181) experienced significantly better DMFS (5-year 91.6% vs. 80.5%, P < 0.001). In subgroup analysis, we found that patients with low SUV-N / SUV-T had significantly better outcomes in T1-2 category (5-year DMFS 98.1% vs. 86.1%, P = 0.002), T3-4 category (5-year DMFS 86.2% vs. 71.5%, P = 0.010), N2-3 category (5-year DMFS 86.2% vs. 75.3%, P = 0.048), and stage IVA-B (5-year DMFS 85.4% vs. 69.8%, P = 0.012). Multivariate analysis showed that SUV- N / SUV-T was an independent prognostic factor for DMFS (HR 2.20, 95% CI 1.20–4.03, P = 0.011).

Conclusion Feasibility of submandibular gland transfer and geometric, as well as dosimetric stability of the gland have been demonstrated. A significant dosimetric sparing of the transferred gland was achieved with a potential for preserving resting saliva flow. For a small subset of patients image guidance with emphasis on monitoring head tilt and lower jaw position are required to maintain transferred gland sparing. A study comparing salivary function in patients receiving submandibular gland transfer vs patients not receiving the transfer is currently in progress. PO-0809 Lymph flow guided radiotherapy for oral tongue cancer: histological verification of the concept S. Novikov 1 , P. Krzhivitckiy 2 , Z. Radgabova 3 , S. Kanaev 2 , M. Kotov 3 , A. Artemyeva 4 , O. Ponomareva 2 , M. Girshovitch 2 , J. Melnik 2 1 Prof. N.N. Petrov Research Institute of Oncology, Radiotherapy, St. Petersburg, Russian Federation ; 2 Prof. N.N. Petrov Research Institute of Oncology, Radiotherapy, St Petersburg, Russian Federation ; 3 Prof. N.N. Petrov Research Institute of Oncology, Head and neck cancer, St Petersburg, Russian Federation ; 4 Prof. N.N. Petrov Research Institute of Oncology, Pathological anartomy, St Petersburg, Russian Federation Purpose or Objective to validate the concept of lymph flow guided radiotherapy by comparison SPECT-CT topography of sentinel lymph nodes (SLN) with uptake of 99mTc-colloids and localization of metastatic lymph nodes (LN) determined by histological examination after standard LN dissection and/or observation. Material and Methods 27 consecutive patients with T1-2N0 clinical stage of oral tongue cancer were eligible for inclusion in this prospective single center study. SLN mapping was obtained by injection of 99mTc-nannocolloids (100-150MBq in 0.3- 0.4ml) in 4 points around the primary lesion. SLN were determined as all LN with radiocolloids uptake. Topography of SLN was determined by SPECT-CT visualization that started 60-120 min after injection of