Virtual Library
Start Your Search
N. Groom
Author of
-
+
P1.07 - Poster Session/ Small Cell Lung Cancer (ID 221)
- Event: WCLC 2015
- Type: Poster
- Track: Small Cell Lung Cancer
- Presentations: 1
- Moderators:
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
-
+
P1.07-009 - Effect of Accurate Heart Outlining on Cardiac Dose - the CONVERT Trial Experience (ID 1378)
09:30 - 09:30 | Author(s): N. Groom
- Abstract
Background:
RTOG 0617 showed greater one year overall survival of 81% in the 60Gy group versus 70.4% in the 74Gy group, supporting the hypothesis that cardio pulmonary effects of radiotherapy can contribute to death. It has demonstrated that the percentage of heart receiving ≥5 and ≥30Gy is correlated with survival. Hence there is a need to improve planning and delivery of radiotherapy to avoid irradiating normal lung and heart wherever possible. This current study investigates the effect on cardiac dose of inaccurate cardiac outlining (non compliant to protocol) for a selection of plans submitted as part of the CONVERT Trial quality assurance programme.
Methods:
The CONVERT Trial is a multicentre phase III study which recruited 547 patients with limited-stage small cell lung cancer from April 2008 to November 2013. Patients were randomised to receive once daily (66Gy in 33 fractions) or twice daily (45Gy in 30 fractions) radiotherapy concurrently with chemotherapy. The primary endpoint was overall survival. The spinal canal, lungs, oesophagus and heart were contoured as organs at risk for dose-volume histograms. The trial protocol specified that the heart and pericardial sac should be contoured. Outlining should extend superiorly to the inferior aspect of the aortic arch and inferiorly to the apex of the heart. An atlas was provided to each centre which included example organ at risk contours. In this current study, heart outline volumes (in cm[3]) provided by participating centres have been compared to gold standard heart outlines (in cm[3]) drawn according to the trial protocol for 50 patients. The impact of the change in heart volume on heart dose (V30) is also presented. The CT and structure set for each case was imported into Eclipse (Version 11), and the heart was re-outlined according to the trial protocol. The plan data were then imported into Vodca along with the dose cube provided by the centre so that DVH data could be extracted.
Results:
The mean difference in cardiac volume between the gold standard and that provided by the centre was 80.0cm[3 ](range: 1.9cm[3] to 248.2cm[3]). In the experimental trial arm (66Gy), an increase in calculated cardiac dose (V30/%) was seen in 22/28 cases (78.6%) by using the gold standard cardiac outline rather than that provided by the centre. The mean increase in V30 was 5.7% (range: 0.92% to 15.29%). In the control dose arm (45Gy), an increase in calculated cardiac dose (V30/%) was seen in 17/22 cases (77.3%). The mean increase in V30 was 6.9% (range: 0.93% to 14.1%).
Conclusion:
In this study we have shown that in 86% of cases reviewed the heart was not delineated according to protocol. As a result the mean heart dose was underestimated by an average of 2.3Gy. In conclusion, this study highlights the importance of collecting radiotherapy plans to check heart contours as part of a QA programme and to feedback deviations to investigators.
