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S. Senthi
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P2.03 - Poster Session/ Treatment of Locoregional Disease – NSCLC (ID 213)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.03-026 - Assessing the Risk of Cardiac Toxicity with Esophageal-Sparing Intensity Modulated Radiotherapy for Locally Advanced Lung Cancers (ID 2646)
09:30 - 09:30 | Author(s): S. Senthi
- Abstract
Background:
Intensity-modulated radiotherapy (IMRT) can be used to reduce high doses to the esophagus for locally advanced non-small cell lung cancer (NSCLC), at the cost of increasing low to intermediate doses to adjacent healthy organs. Care is generally taken to ensure dose to healthy lung is minimized, resulting in IMRT not increasing lung toxicity. Such measures are not normally taken for the heart. Recently, a trial evaluating dose-escalated radiotherapy (RTOG 0617) found that overall survival was impacted by increased low (5Gy) and intermediate (30Gy) cardiac doses. We evaluated the impact of esophageal-sparing IMRT on cardiac doses and predicted toxicity compared to conventional radiotherapy (CRT).
Methods:
Ten consecutive patients with N2 Stage III NSCLC treated to 60Gy in 30 fractions, between February 2012 and September 2014, were evaluated. For each patient, CRT and esophageal-sparing IMRT plans were generated (Eclipse, Anisotropic Analytical Algorithm v11.0.31). For IMRT, treatments were planned such that no radiotherapy beams entered the contralateral lung or heart whenever possible. To compare CRT and IMRT plans, the dose delivered to more than 95% of the target (D~95%~) was compared. Doses to the esophagus, lung and heart were compared by determining the volume receiving X dose (V~XGy~) and the normal tissue complication probability (NTCP).
Results:
Seven patients had Stage IIIA disease, while three had Stage IIIB. The median PTV size was 435.5cc (range 175.0-1309.5). CRT treatment plans used 3-4 fields. IMRT plans had the same (30%), one additional (50%) or two additional fields (20%). Dosimetric and NTCP results are summarized in the table below. IMRT resulted in satisfactory target coverage in 90% of patients. In the one patient with unsatisfactory coverage, the target was adjacent to the spinal cord and IMRT improved the D~95% ~from 42.6Gy to 54.3Gy. Esophageal-sparing was achieved in every patient at all dose levels. There were statistically significant reductions in V~40Gy~ and V~50Gy~ and the NTCP for grade 2 or higher toxicity. IMRT decreased low and intermediate heart doses significantly compared to CRT. This translated into a significantly lower NTCP for cardiac mortality. The cost of this was increased low dose (5Gy) lung exposure, however this did not reach statistical significance, nor did it worsen NTCP for grade 2 pneumonitis.CRT IMRT p-value Mean Dose (Gy) Target D~95%~ 55.9 57.5 0.20 Esophagus V~60Gy~ 3.5 0 0.17 Esophagus V~50Gy~ 32 22.9 <0.01 Esophagus V~40Gy~ 36.4 27.4 <0.01 Heart V~30Gy~ 21.2 15.8 0.03 Heart V~5Gy~ 45.7 39.1 0.01 Lung V~20Gy~ 22 21.9 0.95 Lung V~5Gy~ 45.5 48 0.28 NTCP (%) Esophagus 15.4 9.9 <0.01 Heart 5.7 2.8 0.01 Lung 10.0 8.5 0.02
Conclusion:
Esophageal-sparing IMRT for locally advanced NSCLC can additionally achieve cardiac-sparing and reduce the theoretical risk of cardiac death. With careful consideration this can be achieved without compromising target coverage or increasing the risk of radiation pneumonitis.
