ESTRO 2021 Abstract Book

S792

ESTRO 2021

Research Centre, New Delhi, Radiation Oncology, Delhi, India

Purpose or Objective Intensity modulated radiotherapy (IMRT) has proven advantages over conventional radiotherapy in head and neck cancers (HNC). Simultaneous Integrated Boost (SIB) is yet another concept which has been incorporated in IMRT and has gained popularity by virtue of its ability to provide tailored and differential doses to two or more targets according to risk of harboring cancer cells, keeping total numbers of fractions same for all targets. However, in order to deliver SIB-IMRT there is no consensus yet on what is the optimum number of clinical target volumes (CTV) to be delineated. A common practice in european centres is to create 2 CTVS, high-risk and low-risk. However, most american centers believes that there exist another region just adjacent to high-risk CTV which requires higher dose than that for low-risk CTV. The aim of this study was to compare two-dose levels CTV SIB-IMRT (2CTV-IMRT) and 3CTV-IMRT with regard to treatment outcomes and toxicities. Materials and Methods One hundred and twenty patients with locally advanced HNC were randomized equally into 2CTV-IMRT and 3CTV-IMRT. Dose-fractionation schedule in 2CTV-IMRT was 70 Gy and 50 Gy 35 fractions to gross disease and elective target respectively. Dose-fractionation schedules in 3CTV-IMRT were 70 Gy, 63 Gy and 56 Gy in 35 fractions to gross disease, intermediate risk and elective target respectively. Concurrent weekly cisplatin at 40mg/m 2 was given to all patients if found fit for it. The end points for this study were loco-regional control (LRC), overall survival (OS), acute and late toxicities. LRC and OS were computed with Kaplan-Meier curve with log-rank test for comparison between the two groups. Univariate analysis and Multivariate Cox proportional hazards regression analysis was performed to estimate the impact of known relevant prognostic factors on LRC and OS. Results The median follow up was 28.12 months in 2CTV-IMRT and 31.67 months in 3CTV-IMRT group. The median LRC was statistically non-significant (36.12 in 2CTV-IMRT vs 49.65 months in 3CTV-IMRT; p =0.211). The difference in 3 years LRC was non-significant (37.01 in 2CTV-IMRT vs 52.09% in 3CTV-IMRT; p =0.531). The median OS was 41.21 months in 2CTV-IMRT and 57.33 months in 3CTV-IMRT group, a statistically non-significant difference in OS distribution, χ 2 (2) = 1.89, p =0.365 respectively. The difference in 3 years OS was non-significant (43.82 vs 62.11%; p =0.354). In univariate cox regression model, the two treatment techniques were not found to be associated significantly with LRC and OS. There were no significant differences between the two techniques with respect to acute toxicities of grades ≥3 and late toxicities of grades ≥3. Conclusion 2CTV-IMRT is comparable with 3CTV-IMRT with regard to LRC, OS, acute toxicities and late toxicities. Hence, creating an additional target volume with 63 Gy in 3CTV-IMRT carries no benefit. 2CTV-IMRT being a simple dose-fractionation schedule and less time consuming for delineation may be considered over 3CTV-IMRT. PO-0951 Effects of COVID-19 during radio(chemo)therapy in head and neck cancer patients A. Bandurska-Luque 1 , T. Winiecki 1 , M. Żmijewska-Tomczak 2 , R. Poźniak-Balicka 3 , A. Adamska 2 , T. Bajon 1 , D. Borowczak 1 , P. Milecki 4,5 , J. Kaźmierska 1,4 1 Greater Poland Cancer Centre, Radiotherapy Department II, Poznań, Poland; 2 Greater Poland Cancer Centre, Radiotherapy Department I, Poznań, Poland; 3 Collegium Medicum of University of Zielona Góra, Department of Radiotherapy - University Hospital Zielona Góra, Zielona Góra, Poland; 4 Poznan University of Medical Sciences, Department of Electroradiology, Poznań, Poland; 5 Radiotherapy Department I, Greater Poland Cancer Centre, Poznań, Poland Purpose or Objective To evaluate effects of COVID-19 during (chemo)radiation (RT) or quarantine on overall treatment time and outcome, as well as to determine prognostic parameters for COVID-19 related death in patients with head and neck cancer (HNC). Materials and Methods We have performed a retrospective review and identified patients with confirmed SARS-CoV-2 or quarantine during RT of HNC, who were treated in 3 radiotherapy departments from March 2020 till February 2021. The quarantine was imposed due to a close contact with COVID-19 positive person e.g. after hospitalisation in the same patient’s room. Univariate analysis was performed using a Cox proportional hazards model for COVID-19 positive patients. The covariates included were age, co-morbidities, smoking, white blood cell (WBC) ratio measured on the day of positive COVID-19 test result divided by WBC count taken one week before, C-reactive protein (CRP) ratio, which was obtained analogically to WBC ratio. WBC-ratio and CRP-ratio were chosen to reflect dynamics of possible changes in inflammatory parameters. Results 36 patients (pts) were included in the analysis. Mean age yield 66 years (Range: 25-87). 92% of pts, were treated with curative intent. Two patients had induction chemotherapy and 9 pts got simultaneous chemoradiation. The median follow-up was 3.4 month (Range: 1-5.6). In total 7 patients died, 5 of them were categorised as COVID-19 related death. The time lapsed from a COVID-19 positive test result to death varied in these 5 pts from 8 to 17 days. 26 (72%) pts had SARS-CoV-2 infection confirmed and in the case of 10 pts RT was interrupted due to imposed quarantine. The median interruption time of RT yield 20 days (13-65) and 14 days (10-19) due to COVID-19 and quarantine, respectively. 36% patients did not continue RT due to various reasons including death (5 pts) and deterioration of performance status (3 pts). We did not observe a significant correlation between age, hypertension, performance status, intention to treat (primary vs adjuvant vs palliative), smoking, number of RT fractions before COVID-19 infection, ischaemic heart disease, pulmonary disease, uncontrolled diabetes and risk of COVID-19 related death on univariate Cox analysis. However, in a subgroup of patients (n=17) with available regular blood analysis data WBC-ratio correlated significantly with risk of COVID-19 related death (p=0.02). CRP-ratio did not show