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P1.02 - Poster Session/ Treatment of Localized Disease – NSCLC (ID 209)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Localized Disease - NSCLC
- Presentations: 1
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
P1.02-034 - Lung v5 Does Not Predict for Lung Toxicity after Fixed-Beam Intensity Modulated Radiotherapy (IMRT) (ID 709)
09:30 - 17:00 | Author(s): M. Bewley
Intensity Modulated Radiotherapy (IMRT) facilitates superior dose conformity, due to sculpting of the high dose volume and reduction of dose to normal tissues. However, the use of IMRT for lung cancer in the U.K. remains low, as a result of the paucity of clinical data and concerns about the impact of the low dose bath on toxicity. Our institution has treated 738 lung cancer patients with IMRT since 2008. Here we report the results of 227 patients, focusing on toxicity. Survival will be reported at a later date.
A retrospective review of the first 227 patients receiving 6MV inversely planned (6-8 field) step and shoot IMRT for lung cancer from 2008-2013 was carried out. A database was interrogated to correlate planning parameters with toxicity. Toxicity was collected using Common Terminology Criteria for Adverse Events (CTCAE) version 3.0.
227 patients with a median age of 66 (36-87) were included. Patients received a dose of 50-68 Gy in 20-33 fractions. One hundred and sixty (70%) had non-small cell lung cancer, 47 (21%) small cell lung cancer, 8 (4%) mixed histology and 12 (5%) no histology. At presentation, 6 (3%), 27 (12%), 184 (81%) and 9 patients (4%) had stage I, II, III and IV disease respectively. Treatment modalities were split evenly between concurrent (37%), sequential (31%) chemo-radiotherapy and radiotherapy alone (32%). Median PTV volume was 502.7 cc (67.3-1297.2). Median lung V20, V10 and V5 were 27.7% (6.8-35.3), 50.4% (9.8-83.1) and 64.3% (12.9-98.9). Mean dose to the oesophagus was 23.8 Gy (3.1-51.0); oesophageal V55 and V35 were 2.9% (0-70.8) and 36.8% (0-79.8). Heart V30 and V5 were 23.6% (0-60.6) and 57.6% (0-100) respectively. Despite 104 patients (46%) with V5 values > 65%, acute G3 pneumonitis was observed in only 7 (3.1%) patients. Acute G3 oesophagitis was observed in 31 (13.7%) patients. Late toxicity was not available in all patients. 6/154 (4%) developed late G3 pneumonitis, 8/154 (5.3%) had late G3 dyspnoea and late G2 cough was reported in 12/154 (8.1%). Grades 1, 2 and 3 pulmonary fibrosis occurred in 68/178 (30%), 13/178 (6%) and 1/178 (0.4%) patients respectively. Oesophageal stricture was evident in 7/173 (3%) and 4 patients developed an oesophageal fistula. There was no significant correlation between lung V5 and acute or late lung toxicity, using >65% as a cut off. Similar results were found with lung V10. There was also no relationship between mean oesophageal dose/V35/V55 and fistula or oesophageal stricture.
From our experience, IMRT to the thorax is well tolerated, with minimal grade 3 toxicity. Contrary to reports, we did not observe a correlation between lung V5 and acute/late lung toxicity. However the heterogeneous population, retrospective nature of this study and small number of grade 3+ events limit the scope for multivariate analysis of toxicity. The data needs to be confirmed with a larger number of patients and integrated within predictive models of radiation-induced toxicity using patient reported outcome tools to facilitate collection of prospective toxicity data in the routine clinical setting. Data will be updated prior to the meeting.
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