ESTRO 2020 Abstract book

S483 ESTRO 2020

(HR 0.83, 95%CI 0.685-0.999, p=0.049). Using an empiric cut-off at the 25th percentile of MPV distribution (9.7fL), Kaplan Meier analysis demonstrated a significantly decreased CSS (p=0.012), LC (p=0.002) and RFS (p=0.004) for patients with a low (<9.7fL) MPV. Conclusion Our findings indicate that the MPV is a prognostic marker in OPSCC patients and may contribute to future individual risk assessment in patients with OPSCC. PO-0808 Geometric and dosimetric evaluation of submandibular gland sparing following gland transfer V. Moiseenko 1 , T. Atwood 1 , C. Coffey 2 , P. Hua 1 , M. Cornell 1 , P. Sanghvi 1 1 University of California San Diego, Radiation Medicine and Applied Sciences, La Jolla, USA ; 2 University of California San Diego, Head and Neck Surgical Oncology, La Jolla, USA Purpose or Objective Xerostomia is associated with radiotherapy (RT) of head- and-neck (HN) cancers. Resting saliva is mostly derived from submandibular glands and for patients with unilateral disease gland transfer has been advocated as a means to preserve salivary function. To achieve this preservation significant dose reduction to the gland is required in RT planning, and stability of the gland through the course of RT has to be established. We evaluated geometric stability and dose to the transferred gland in HN cancer patients planned and treated with sparing of the transferred gland. Material and Methods A case-control study is currently in progress at UCSD. Head and neck cancer patients with unilateral disease are eligible for submandibular gland transfer, with RT plans specifically designed to spare the transferred gland. Patients are followed up and their salivary function is assessed by collecting stimulated and resting saliva as well using questionnaires for quality of life. Seven patients thus far have received gland transfer and completer RT. Patients were treated on the Halcyon linear accelerator with daily CBCT for realignment. CBCTs were imported in MiM for contouring, co-registration with the planning CT and quantification of positional and dosimetric stability. Transferred gland was contoured on one CBCT from each week. Coordinates of the center of mass (COM) were calculated in three directions from the isocenter and mean dose was calculated by overlaying the dose from the original plan. Results Significant dosimetric sparing of the transferred submandibular gland was achieved in planning with the mean dose to spared gland of 15.4±3.4 Gy. The non-spared gland was typically fully contained within low or intermediate PTV, receiving full prescription dose. In most cases the gland position was stable through the treatment with mean COM deviations 1.5±2.5mm, 4.5±2.8mm and 4.7±1.3 mm in lateral, ant/post and sup/inf directions. Figure 1 shows the sparing of the transferred gland in planning and four contours from CBCTs. For a small subset of patients COM deviations of the order of 1 cm in all directions were noted. These were attributed to head tilt and lower jaw position. Because the transferred gland is located close to high dose gradient this misalignment led to mean dose increase by approximately 15 Gy.

p=0,0428; HR<100 10³/µl eosinophil: 1,9948, IC 95% 1,0225 to 3,8914, HR>100 10³/µl eosinophil: 0,5013, IC 95% 0,2570 to 0,9780).Among p16-ve patients, mean OS was 22.2 months in <100 10³/µl eosinophil group vs 50.2 months in >100 10³/µl group; Chi-squared test: P= 0,0041; HR<100 10³/µl eosinophil: 0,1207, IC 95%: 0,02845 to 0,5124; HR>100 10³/µl eosinophil: 8,2818, IC 95% 1,9515 to 35,1469.

Conclusion In that study we observed a better prognosis in p16+ve patients with <100 10³/µl eosinophil and in p16- patients who had >100 10³/µl eosinophil. Results about p16+ve patients are aligned with literature’s data on cervical cancer. Notably p16 status provides opposite prognosis in relation to eosinophil values: in p16+ group there was a better prognosis in patients with eosinophil <100 10³/µl, in p16- there was a better prognosis in who had >100 10³/µl eosinophil at baseline with statistically significant differences in both arms. This study offers preliminary evidence that eosinophil value at the baseline can represent one more prognostic factor for patients with OPSCCs. PO-0807 The association between mean platelet volume and prognosis in patients with oropharyngeal cancer. T. Langsenlehner 1 , K. Lukasiak 1 , E. Thurner 1 , D. Delago 1 , O. Knittelfelder 1 , H. Stranzl-Lawatsch 1 , G. Jakse 1 , W. Renner 2 1 Medical University of Graz, Department of Radiation Oncology, Graz, Austria ; 2 Medical University of Graz, Clinical Institute of Medical and Chemical Laboratory Diagnostics, Graz, Austria Purpose or Objective Altered mean platelet volume (MPV) has been associated with prognosis in different types of cancer, however, its prognostic role in head and neck cancer is largely unknown. In the present study, the prognostic significance of the MPV was analyzed in 319 oropharyngeal squamous cell cancer (OPSCC) patients treated at a tertiary academic center. Material and Methods Data from 319 consecutive non-metastatic OPSCC patients treated at a single tertiary academic center were included in this retrospective study. The prognostic impact of the MPV for cancer-specific survival (CSS), locoregional control (LC) and recurrence-free survival (RFS) was assessed using the Kaplan-Meier method as well as uni- and multivariate Cox proportional hazards models. Results The median MPV was 10.30 fL (mean 10.26 ± 1.17fL), respectively. Univariate analyses showed a significant association of the MPV with CSS (HR 0.85, 95%CI 0.74-0.98, p=0.025), LC (HR 0.86, 95%CI 0.74-0.99, p=0.034) and RFS (HR 0.87, 95%CI 0.76-0.996; p=0.043). In multivariate analysis, the AST/ALT ratio remained an independent prognostic factor for CSS (HR 0.77, 95%CI 0.63-0.93, p=0.008), LC (HR 0.80, 95%CI 0.65-0.98, p=0.030), and RFS