Abstract Book

S1251

ESTRO 37

treatment is now continuously triggered, obtained, mathematically analyzed and compared with the CBCT offline calculated offset. EP-2390 Temporal Changes Of Target Volumes and Oar Volumes During High Precision Radiotherapy D. Dhar 1 1 apollo Gleneagles Hospitals, Radiation Oncology, Kolkata, India Purpose or Objective Tumor shrinkage in response to radiotherapy, change in OAR (organ at risk) volume and weight loss may impact on the dose-distribution in both target & organ at risk (OAR) and hence the therapeutic outcome in patients with Head & Neck cancer. In this study, we investigated temporal changes of the target volumes & OAR volume during radiotherapy to adopt a strategy for adaptive radiotherapy. Material and Methods Twenty-six patients who underwent radical chemo- radiotherapy (CTRT) for head & neck squamous cell carcinoma between April’12-April’13 were prospectively analyzed. After immobilization, Computed Tomography (CT) scans were taken from base of the skull to sternal angle using 3mm slices by Siemens Somatom Emotion 16 slice CT scanner. Targets and OAR were contoured using Focal Sim. Treatment Planning was done on the XiO Treatment Planning System (ELEKTA AB, Sweden). All patients underwent 3D-CRT/IMRT. The prescription dose was 59.4 Gy-70Gy @ 1.8 -2Gy/fraction. All patients underwent a CT scan after 20 fractions. Targets and organs at risk were similarly outlined on these scans as above.The cranio-caudal dimensions of the planning target volume (PTV) were kept the same. Only the part of PTV going out of body contour (due to weight loss) was changed.Volume changes of targets and OARs were analyzed using SPSS 16. Results Comparison between both CT-scan (planning CT & CT at 20th fraction.) showed changes in GTV (mean24.56ccVs19.86cc p<0.001 , 95%CI 2.86-6.54), PTV (mean280.44ccVs255.1cc p=0.48, 95% CI -3.36-6.93), right Parotid (mean27.43ccVs22.25cc p<0.001 , 95%CI 3.44-6.90) and left Parotid (mean25.38cc Vs 20.97cc p<0.001 , 95% CI 2.81-5.99) volumes. Conclusion After 4-5 weeks of adjuvant chemo-radiotherapy, it is commonly found that there is reduction in body weight due to oral mucositis. As a result, there is a change in the patient’s contour and the relative positions of the GTV/PTV and OARs may change. In the present study, we have found significant changes in GTV volume (p<0.001), and also change in OAR volume, which in this case is the parotid glands (p<0.001 for both left and right parotids). On the other hand, the total PTV volume has not been found to change significantly (p=0.48), However, for some patients we have found the PTV volume to extrude outside the body contour. Though the PTV volume does not change appreciably, our findings point to the need for re-planning after repeat CT scan, since some of the OAR’s migrate near or away from the GTV due to change in both GTV as well as OAR volumes, and due to PTV extending beyond body. It is essential to re-plan to identify dosimetric changes and to ensure adequate doses to target volumes and safe doses to normal tissues. Volumetric changes in the target volume and OARs were observed could have potential dosimetric impact when highly conformal treatment techniques are used. It

Suggest that adaptive strategies, where patients are re- imaged & possibly replanned during treatment, are worth evaluating

Electronic Poster: RTT track: Patient care, side effects and communication

EP-2391 Readability of Internet sourced Patient Information Leaflets for Head and Neck Cancer in 3 Regions D. Flinton 1 , K. Haria 2 1 CIty- University of London, Radiography, London, United Kingdom 2 Portsmouth Hospitals NHS Trust, Radiotherapy, Portsmouth, United Kingdom Purpose or Objective As the incidence of head and neck cancer increases and the number of patients receiving radiotherapy increase it is essential that this group of patients like others receive adequate information. The internet has seen a significant increase in its use as a source of information with over 80% of the adult UK population using the internet in 2016 compared with approximately 35% in 2006, an increase that is also reflected in other countries. One of the main uses of the internet, particularly in the older population is as a source of healthcare information.

Material and Methods

A simple Google search emulating how patients may search for information regarding head and neck radiotherapy was undertaken. Results were limited to information being provided by hospitals and countries whose first language was English. A total of 39 webpages were found; 14 from UK & Ireland, 14 - USA & Canada and 11 - Australia & NZ. Readability was assessed using both the Flesch Reading Ease Score (FRES) and Simple Measure Of Gobbledygook (SMOG) both of which are part of the output provided by the software Readability Studio. The FRES score utilises a 0–100 scale with higher scores indicating text that is easier to read. The SMOG test result returns a reading grade which equates to the U.S. school grade level. Results PIL’s varied largely in the information that was included, the majority of PIL’s across all regions captured all relevant information within one PIL, whilst others created different PIL’s for each aspect of the radiotherapy treatment; and as a result, this led to a difference in size and content of each PIL. Each region had a large variation in the total number of words, range of words, word complexity and average sentence length. The mean FRES scores for the UK & Ireland, USA &