ESTRO 2021 Abstract Book

S798

ESTRO 2021

statistically significant negative impact on OS (p=0.005) on univariate analysis. Multivariate analysis showed GTV-Pvol to be independently predictive for OS (HR 1.48) and EFS (HR 1.19), while, PETCT maximum standardized uptake value (SUVmax) for EFS (HR 1.38). Conclusion The results of this exclusive analysis of PCUE cancers, though better than previous retrospective data, still reflects the dismal prognosis associated with this subsite. Organ-preservation studies in future should aim at utilizing (i) tumor volumetric and metabolic parameters (for better patient-selection), (ii) IM-IGRT (to improve therapeutic ratio and dose escalation) and (iii) rigorous speech and swallowing rehabilitation, to further improve outcomes in PCUE cancers. PO-0958 Comparison of CCRT and RT alone after Induction Chemotherapy for Hypopharyngeal Cancer M. Wan 1 , D. Zhao 1 , B. Zheng 1 , S. Xiao 1 , Y. Sun 1 , W. Wang 1 1 Peking University Cancer Hospital and Institute, Beijing 100142, People’s Republic of China, Department of Radiation Oncology, Beijing, China Purpose or Objective This study was aimed to compare the efficacy and toxicities of induction chemotherapy (IC) followed by concurrent chemoradiotherapy (CCRT) or radiotherapy alone (RT) in patients with locally advanced hypopharyngeal squamous cell carcinoma (HPSCC). Materials and Methods A total of 141 patients with HPSCC was screened in history system (August 2008 to October 2020), of which 83 locally advanced HPSCC patients were eligible for data analysis in our study. All the 83 patients received IC. Subsequently, 52 patients underwent CCRT and 31 received RT alone. Efficacy assessment was conducted by Response Evaluation Criteria in Solid Tumors (RECIST version 1.1) Criteria. Patients were divided into two groups according to results of efficacy assessment to IC: the IC responders with complete response (CR) and partial response (PR) and the IC non-responders with stable disease (SD) and progressive disease (PD). Survival, patterns of recurrence, and toxicities were analyzed. Results The median follow-up was 30.2 months. In the IC responder cohort, 3-year locoregional relapse-free survival (LRRFS) (74.7% vs 57.0%, P=0.049) and overall survival (OS) (58.3% vs 25.5%, P=0.027) were significantly improved in patients received IC+CCRT, compared to patients received IC+RT. But no significant differences were found on the 3-year distant metastasis-free survival (DMFS) (70.2% vs 79.2%, P=0.651) and progression- free survival (PFS) (50.3% vs 48.0%, P=0.092). Multivariate analysis confirmed that IC followed by CCRT (hazard ratio: 0.36, 95% confidence interval: 0.14-0.92, P=0.033) was a prognostic factor with OS. However, for all patients or IC non-responders, IC + CCRT did not improve the LRRFS, DMFS, PFS, and OS, compared to IC + RT. During (chemo)radiotherapy, except for that≥2 grade leucopenia occurred more in IC+CCRT group (55.8% vs. 25.8%, P=0.008) than in the IC+RT alone group, other toxicities were not under statistical difference. Conclusion In terms of IC responders, CCRT might lead to the OS benefit comparing to RT alone. Also, the toxicities of all patients were manageable during the therapy. PO-0959 A study correlating type of tobacco use with dosimetry of parotids in H&N patients treated with IMRT N. Patil 1 , S. Lewis 1 , U. V 2 , A. Reddy 1 , A. Singh 1 , P. Augustine 1 , S. Chauhan 1 , K. Sharan 1 1 Kasturba Medical College, Department of Radiotherapy and Oncology, Manipal, India; 2 Kasturba Medical College,, Department of Radiotherapy and Oncology, Manipal, India Purpose or Objective Tobacco chewing is the most common form of tobacco use in India and patients majority present in advanced- stage disease. Achieving parotid sparing with IMRT in these patients is a challenge. We aimed to correlate parotid volume with the type of tobacco use and document dose received by superficial parotids in head and cancer patients treated with radical radiotherapy. Materials and Methods This is a retrospective study that included patients with histological confirmation, treated with curative intent radiotherapy in our center from Jan 2017 to March 2020. The patient's target volume encompassed bilateral neck were included in the study. Patients with Stage I laryngeal cancer, metastatic at presentation, and receiving reirradiation were excluded from the analysis. The medical records of all patients were retrieved and the demographic variables along with physician-assessed Radiation Therapy Oncology Group (RTOG) xerostomia toxicity grades were collected. The delineation of the superficial and deep lobe of the parotid was done retrospectively. All patients were treated with IMRT to a dose of 60-70Gy/30-35 fractions. The Parotids individually and superficial and deep parotids were considered to be spared if the mean dose was less than 26 Gy. Using the dosimetric information we divided our patients into 4 groups. Group 1 includes patients where we achieved bilateral parotid sparing,Group 2 consists of contralateral parotid sparing, Group 3 consists of bilateral or contralateral superficial parotid sparing, while in Group 4 no parotid gland sparing was achieved. The data was analyzed using SPSS 21. A chi-square test will be used to compare the groups. Results One seventy-four patients were included in the study. The median age of the patients was 59 years (IQR 51-66) and 84% were males. Tobacco chewing was the most common form of use (51%) followed by smoking (35%) and other forms (6%). 81% were locally advanced with stage III and IV. The oropharynx (30%) and hypopharynx (28%) were the most common sites involved. Bilateral parotid sparing was achieved in 37% and contralateral in 25%. Superficial parotid sparing was achieved in 27%. The mean dose to parotids in these patients was 25 Gy and V26 Gy was 39%. The median parotid volume was 53cc (range 18-130cc). The parotid volume was smaller in patients with tobacco chewing compared to smokers (51% vs 38%) however p-value was not significant