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A. Sheikh
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MINI 18 - Radiation Topics in Localized NSCLC (ID 139)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Treatment of Localized Disease - NSCLC
- Presentations: 1
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MINI18.12 - Assessment of Dose Response via Regional Lung Perfusion following Stereotactic Radiotherapy for Lung Cancer (ID 910)
17:50 - 17:55 | Author(s): A. Sheikh
- Abstract
- Presentation
Background:
Radiation therapy (RT)-induced lung injury is one of the major causes of morbidity in patients with thoracic cancer. Extensive work has been done to understand the predictors of lung injury in patients receiving conventionally fractionated RT. However, less work has been done in the setting of hypo-fractionation. Further, conventional methods to consider lung injury typically assess global lung function (e.g. symptoms, pulmonary function tests), are affected by many other (non-radiation) factors, and are thus non-specific. Single photon emission computed tomography (SPECT) perfusion imaging affords an objective quantitative manner to assess the effects of RT on regional lung function. We herein report the preliminary results of a prospective study to assess the magnitude of RT-induced reductions in regional lung perfusion following hypo-fractionated stereotactic RT.
Methods:
Four patients undergoing hypo-fractionated stereotactic lung RT (SBRT: 12 Gy x 4 fractions or 10 Gy x 5 fractions) had a pre-treatment SPECT (single-photon emission computed tomography) perfusion scan providing a 3D map of regional lung perfusion. Scans were repeated 3-6 months post-treatment. Pre- and post SPECT scans were registered to the planning CT scan (and hence the 3D dose data). Changes in regional perfusion (counts per cc on the pre-post scans) were computed in regions of the lung exposed to different doses of radiation (in 5 Gy intervals), thus defining a dose-response function. SPECT scans were internally normalized such that total counts in the regions receiving <5 Gy were equal between pre- and post-treatment scans.
Results:
3 months post-RT, changes in perfusion are highly variable. At 6 months, there is a consistent dose-dependent reduction in regional perfusion. Average percent decline in regional perfusion was 10% at 15-20 Gy, 20% and 20-25 Gy, and 30% at 25-30 Gy representing a relatively linear dose response with an approximate 2% reduction per Gray for doses in excess of 10 Gy. Subtle increases in perfusion were seen in lung receiving <10 Gy. Figure 1
Conclusion:
Hypo-fractionated stereotactic RT appears to cause a dose-dependent reduction in regional lung perfusion. There appears to be a threshold effect with no apparent perfusion loss at doses <10 Gy, in both normalized and unnormalized dose-response curves. Additional data is needed from a larger number of patients to better assess this issue. This sort of data can be used to assist optimizing RT treatment plans that minimize the risk of lung injury.
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P2.11 - Poster Session/ Palliative and Supportive Care (ID 230)
- Event: WCLC 2015
- Type: Poster
- Track: Palliative and Supportive Care
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.11-008 - Association between Heart/Lung Dosimetric Parameters and Subsequent Changes in Quality of Life in Patients Receiving Thoracic Radiotherapy (ID 2549)
09:30 - 09:30 | Author(s): A. Sheikh
- Abstract
Background:
Thoracic radiotherapy can negatively affect cardiopulmonary function. We herein report on a prospective assessment of the association between heart/lung dosimetric parameters and subsequent changes in the quality of life (QOL) in patients receiving thoracic radiotherapy.
Methods:
Patients about to initiate a course of 3D-planned external beam RT for tumors in/around the thorax were prospectively studied as part of an IRB-approved clinical study. Written informed consent was obtained. Patients had assessments of cardiopulmonary QOL pre-RT and serially post-RT (e.g. 1.5, 3, 6, 12... months post-RT) using the Functional Assessment of cancer Therapy-Lung (FACT-L) questionnaire. An association between a variety of dosimetric parameters for the heart and lungs (e.g. mean dose, Vx) and changes in pulmonary QOL (e.g. declines in QOL; pre-RT minus post-RT values) were assessed using univariate and multivariate techniques.
Results:
The data from 24 patients treated between 2009-2013 and with evaluable QOL were studied. Their demographics are as follows: median age 68 (range 48-87), 46% male, 92% white, 98% primary tumor from lung, 70% stage III or IV, 50% current or former smokers, 67% having no coexisting lung or heart disease before, 42% also receiving chemotherapy. For the overall group, there were no statistically significant differences between the pre-RT value (QOL score 80.6) and any of the post-RT time points (QOL scores 79.9, 79.9 and 76.3 at 1.5, 3 and 6 months post-RT, respectively). On a per-patient basis, there were no significant associations between any of the lung or heart dosimetric parameters and subsequent declines in QOL, though there was a non-significant trend towards greater declines in QOL with larger lung doses (e.g. mean, V20 and 30). There were no similar trends seen with the heart-based dosimetric parameters. When limiting the analysis to patients whose QOL score declined post-RT, there was a positive correlation between the degree of decline and the V30 and V40 of heart (p＜0.05). Among patients with lung cancer, the degree of decline in QOL was associated with the heart V20, V30, V40 (p＜0.05).
Conclusion:
There are no significant associations seen between lung and heart dosimetric parameters and subsequent declines in QOL. Additional analyses involving a larger number of patients are needed to better define predictors of RT-associated declines in QOL. (Supported in part by National Institutes of Health Grant CA69579 , a grant from the Lance Armstrong Foundation)
