ESTRO 38 Abstract book

S638 ESTRO 38

EP-1150 Dosimetric benefit on adaptive IMPT for patients with locally advanced nasopharyngeal carcinoma W.W. Lam 1 , H.F.V. Lee 2 , K.Y. Cheung 1 , S.K. Yu 1 1 Hong Kong Sanatorium & Hospital, Medical Physics & Research Department, Happy Valley, Hong Kong SAR China ; 2 The University of Hong Kong, Department of Clinical Oncology- Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong SAR China Purpose or Objective To evaluate the dosimetric impact and benefit on adaptive IMPT (APT) for locally advanced NPC patients due to 11 NPC patients (AJCC stage III & IV) were planned with IMPT using 3 beams with MFO and SIB technique in Eclipse proton TPS. PTVs (PTV 70 and PTV 66 ) were aimed to achieve a V 95% covered by 70 and 66 Gy(RBE), respectively. Patients were scanned by PETCT (ReCT) at 3 rd week additionally to initial planning CT. DIR were performed between the two CT image sets and all deformed contours on ReCT were verified. To quantify the dosimetric impact due to anatomical changes, a non-adapative IMPT plan was created by recalculating the initial IMPT plan on ReCT while an adaptive plan was created by reoptimizing on ReCT to evaluate the dosimetric benefit on APT. D 99.5% and D 95% , CN and HI of PTVs, D max and D 2% of brainstem, spinal cord, optic chiasm, left and right optic nerves and D mean of left and right parotid glands were reported. gEUD and NTCP of OARs were calculated using LKB model. Wilcoxon signed-rank test was used for statistical analysis. A 2- tailed p <0.05 was considered significant. Results No statistically significant difference were found in D 99.5% , D 95% , CN and HI of all PTVs between adaptive and original plan although both PTVs were reduced by 11%( p=0.001 ) on ReCT. The mean D 99.5% , D 95% , CN and HI of PTV 66 were deteriorated by 9.8%( p=0.003) , 3.1%( p=0.003) , 23.0%( p=0.001) and 120.4%( p=0.001) in non-adaptive vs original plan . The mean CN and HI of PTV 70 were worsen by 50.9%( p=0.001) and 120.5%( p=0.001) in non-adaptive vs original plan. No significant difference were found in D max , D 2% , gEUD and NTCP of brainstem, spinal cord, optic chiasm and optic nerves between adaptive and original plan. Significant increase in mean D max , D 2% , gEUD of brainstem by 8.1%( p=0.019) , 10.1%( p=0.014) and 10.7%( p=0.014) were found in non-adaptive vs original plan. The mean NTCP of brainstem was increased from 0.06 to 0.14% ( p=0.01). Significant increase in mean D max , D 2% , gEUD of spinal cord by 25.4%( p=0.001) , 26.7%( p=0.001) and 26.2%( p=0.001) were found in non- adaptive plan. The mean NTCP of spinal cord was increased from 0.08 to 1.3%( p=0.001). Significant increase in mean D max , D 2% , gEUD of optic chiasm by 5.1%( p=0.002) , 5%( p=0.003) and 9.2%( p=0.032) were found in non- adaptive vs original plan. The mean NTCP of optic chiasm was increased from 1.4 to 9.4%( p=0.019). No statistically difference were found in D max , D 2% , gEUD and NTCP of optic nerves in non-adaptive vs original plan. Significant increase in D mean , gEUD and NTCP of parotid glands were found in adaptive and non-adaptive vs original plan. D mean , gEUD and NTCP were significantly reduced by 5.4%, 5.8% and 5.5% for left parotid gland while 9.1%, 9.2% and 18.3% for right parotid gland in adaptive vs non-adaptive plan. anatomical changes. Material and Methods

Conclusion Anatomical changes had a significant dosimetric impact on IMPT plan quality and APT showed dosimetric benefits in both targets and OARs for locally advanced NPC patients. EP-1151 Effects of Continued Smoking in Head and Neck Cancer Patients: A Systematic Review and Meta- Analysis J. Smith 1 , D. Nastasi 1 , R. Tso 1 , V. Vangaveti 1 , B. Renison 2 , M. Chilkuri 3 1 James Cook University, College of Medicine and Dentistry, Townsville, Australia ; 2 The Townsville Hospital, Townsville Health Library, Townsville, Australia ; 3 The Townsville Hospital, Radiation Oncology, Townsville, Australia Purpose or Objective To determine the effects of continued smoking in head and neck cancer (HNC) patients undergoing radiotherapy on overall survival (OS), locoregional control (LRC), quality of life (QoL) and acute and late toxicities. Material and Methods Articles from January 1990 to August 14, 2018 were searched in PubMed, MEDLINE (Ovid), Embase, Scopus, The Cochrane Library, CINAHL and AUSThealth. Articles were included if majority of patients were treated with radiotherapy and smokers were defined as those who continued to smoke during or after radiotherapy. Data extraction and risk of bias assessment was performed by three independent co-authors using summary data of original studies. A meta-analysis using a random effects model was conducted for OS and LRC. In addition, a qualitative synthesis was performed for toxicities and quality of life as only a limited number of articles were available. Results The initial search identified 2,217 studies, with 24 articles comprising 6,332 patients eligible for inclusion. Analysis demonstrated that continued smoking was associated with approximately two times the risk of mortality (RR = 1.85, 95% CI 1.55 – 2.21, p< 0.0001, I 2 = 43%) in HNC patients. Similarly, the risk of locoregional failure was more than two times greater in HNC patients who continued smoking (RR = 2.24, CI 1.42 – 3.52, p = 0.0005, I 2 =64%). The qualitative synthesis indicates that continued smoking may contribute to an elevated incidence of late but not acute toxicities. Conclusion This review provides evidence that continued smoking is associated with a lower OS and LRC and a higher incidence of late toxicities. Therefore, clinicians should strongly encourage smoking cessation amongst all head and neck cancer patients. This abstract is part of the media programme nd will be released on the day of its pr sentation