Abstract book - ESTRO meets Asia

S85 ESTRO meets Asia 2018

pneumonitis. And other complication rates were tolerable which was compared with historical studies. Conclusion High dose radiation is tolerable and contributes to improve outcomes, especially local progression free survival in patients with inoperable stage III non-small cell lung cancer, if radiation field is restricted to gross tumor only. PO-209 Risk of radiation pneumonitis in post-lobectomy lung cancer patients receiving adjuvant radiotherapy W. Chan 1 , C.H. Liu 1 , W.Y. Tin 1 , S.F. Nyaw 1 , K.C. Lee 1 , S.H. Lo 1 , C.S. Wong 1 1 Tuen Mun Hospital, Clinical Oncology, Tuen Mun, Hong Kong SAR China Purpose or Objective Patients who had lobectomy of lung may be more prone to developing radiation pneumonitis given their smaller remaining lung volume. There is no consensus on the normal lung dose constraint in post-lobectomy radiotherapy. Conventionally, dose constraints of V20 ≤ 33% and mean lung dose (MLD) ≤ 20Gy had been used. A recent study by the MD Anderson Cancer Center showed that V10 ≥ 30% and V20 ≥ 20% were predictive of high risk of radiation pneumonitis in post-operative patients. We aim to determine whether V20 ≤ 33% and MLD ≤ 20Gy is a safe constraint in post-lobectomy patients, and to estimate the risk of severe radiation pneumonitis in patients with V10 ≥ 30% and V20 ≥ 20%. Material and Methods The data of all patients who received postoperative radiotherapy after lobectomy in a tertiary referral center from 2011 to 2018 were analyzed retrospectively. The endpoint was CTCAE grade 3 or above radiation pneumonitis. The diagnosis of radiation pneumonitis was made independently by two clinical oncologists. Clinical data of all patients including their demographics and the surgical procedures done were recorded. Radiotherapy treatment details including indication, dose fractionation, delivery technique and use of concurrent chemotherapy were also recorded. Dosimetric parameters including V10 and V20 of whole lung, mean lung dose and PTV volume were recorded and analyzed. Results A total of 55 patients were identified. The median age was 63-year-old. 80% of patients had ECOG 0 or 1. 92.7% of patients were treated with 3D conformal technique, with the remaining treated with IMRT. The most common indications of radiotherapy were N2 stage (52.7%) and microscopic positive or close margin (27.3%). Dose fractionation used included 60Gy/30fr/6 weeks (40%), 54Gy/27fr/5.5 weeks (25.5%) and 50Gy/25fr/5 weeks (18.2%). Chemotherapy was given concurrently in 12.7% and sequentially in 61.8% of patients. 3 patients (5.5%) developed G5 radiation pneumonitis. There was no G3 or G4 pneumonitis. All three patients with G5 pneumonitis were admitted for shortness of breath within approximately 2 weeks after the last fraction (range: 7 - 15 days). Their dosimetric parameters were shown in the table below. All of them were able to meet our dose constraints of V20 ≤ 33% and MLD ≤ 20%. A total of 33 patients, including the 3 patients with G5 pneumonitis, fell into the high risk category of V10 ≥ 30% and V20 ≥ 20% as suggested by MDACC group. This risk of G3 or above pneumonitis in this high risk category was calculated to be 9.1% (3/33). Conclusion Our data showed that the risk of G3 or above radiation pneumonitis was 5.5% in patients who had lobectomy using dose constraint of V20 ≤ 33% and MLD ≤ 20%. This risk increased to 9.1% in patients with V10 ≥ 30% and V20 ≥

20%. Further prospective studies are necessary to identify the optimal dose constraints for this group of patients. PO-210 Conformal or VMAT plans in Non-Small Cell Lung Cancer: Update of dosimetric parameters and outcome N. Abdul Satar 1 , P. Wells 1 , S. Lynch 1 , S. Bowles 1 , K. Yip 2 , J. Conibear 1 1 Barts and the London NHS Trust, Radiotherapy Dept, London, United Kingdom 2 Ipswich Hospital, Radiotherapy Department, Suffolk, United Kingdom Purpose or Objective Advances in lung cancer radiotherapy now permits increased accuracy of tumour targeting through image guided radiotherapy (IGRT) and advanced forms of intensity modulated radiotherapy (IMRT) such as volumetric modulated arc radiotherapy (VMAT), which helps minimise toxicity to normal tissues. We conducted a retrospective analysis to assess the impact of these new technologies on our patients. Material and Methods We compared 2 radical (chemo)radiotherapy patient cohorts treated in our institution; Group A treated from February 2013 - February 2014 and Group B from September 2015 - September 2016. We analysed radiotherapy planning techniques, dose delivered, normal tissue doses and outcomes. Results In Group B, we treated double the number of patients (26) with radical radiotherapy (64Gy/32# or 55Gy/20#) compared to Group A (13). Baseline characteristics were similar; median age 65yrs (A) and 70yrs (B). Most patients had stage III disease (69%-A, 81%-B). 77% of patients in both groups had concurrent cisplatin and vinorelbine chemotherapy. All patients in Group A had conventional CT planning scans and 3D-conformal planning. In Group B, all had 4D-CT planning scans and 85% (22/26) had VMAT plans. Patients treated with 55Gy/20# increased from 23% (3/13-A) to 46% (12/26-B). The median CTV increased from 64cm 3 (range 45cm 3 – 99cm 3 Group A) to 142cm 3 (range 15cm 3 – 656cm 3 Group B), (p-value 0.00005). Despite the increase in CTV, the median PTV remained similar (312cm 3 - A vs 364cm 3 - B). With VMAT plans, the lung doses remained low despite the increase in CTV; lung V20 (22%- A vs 20%-B), lung V5 (49% vs 49%) and mean lung dose (15Gy vs 12Gy). We selected the 5 largest CTVs from group B (CTV range 294 cm 3 – 656 cm 3 ) and compared 3D conformal plans with the respective VMAT plans. We found VMAT allowed optimal dose coverage without compromising the PTV. VMAT benefited large midline tumours most where constraints of cord, heart and brachial plexus were met without PTV compromise. All Group A and 25/26 Group B patients completed their planned treatment. Median overall survival in Group A was 14.5 months and in Group B was 26.4 months (p-value 0.3).