Dataset Information

Dose surface maps of the heart can identify regions associated with worse survival for lung cancer patients treated with radiotherapy.

ABSTRACT:

Background and purpose

For lung cancer patients treated with radiotherapy, radiation dose to the heart has been associated with overall survival, with volumetric dose statistics widely presented. However, critical cardiac structures are present on the hearts surface, where this approach may be sub-optimal. In this work we present a methodology for creating cardiac surface dose maps and identify regions where excess dose is associated with in worse overall survival.

Material and methods

A modified cylindrical coordinate system was implemented to map the cardiac surface dose for lung cancer patients. Validation was performed by mapping the cardiac chambers for 55 patients, fitting a point spread function (PSF) to the blurred edge. To account for this uncertainty, dose maps were blurred by a 2D-Gaussian with width described by the PSF. Permutation testing identified regions where excess dose was associated with worse patient survival. The 99th percentile of the max t-value then defined a cardiac surface region to extract dose, from each patient, to be analysed in a multivariable cox-proportional hazards survival model.

Results

Cardiac surface maps were created for 648 lung cancer patients. Cardiac surface dose maps were blurred with a 2D- Gaussian filter of size ?_? = 4.3° and ?_y = 1.3units to account for mapping uncertainties. Permutation testing identified significant differences across the surface of the right atria, p < 0.001, at all timepoints. The median dose to the region defined by the 99th percentile of the maximum t-value was 18.5 Gy. Multivariable analysis showed the dose to this region was significantly associated with survival, hazard ratio 1.01 Gy^-1, p = 0.03, controlling for confounding variables.

Conclusions

Cardiac surface mapping was successfully implemented and identified a region where excess dose was associated with worse patient survival. This region extended over the right atria, potentially suggesting an interaction with the hearts electrical conduction system.

SUBMITTER: McWilliam A

PROVIDER: S-EPMC7807666 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Publications

Dose surface maps of the heart can identify regions associated with worse survival for lung cancer patients treated with radiotherapy.

McWilliam Alan A Dootson Chloe C Graham Lewis L Banfill Kathryn K Abravan Azadeh A van Herk Marcel M

Physics and imaging in radiation oncology 20200730

<h4>Background and purpose</h4>For lung cancer patients treated with radiotherapy, radiation dose to the heart has been associated with overall survival, with volumetric dose statistics widely presented. However, critical cardiac structures are present on the hearts surface, where this approach may be sub-optimal. In this work we present a methodology for creating cardiac surface dose maps and identify regions where excess dose is associated with in worse overall survival.<h4>Material and method ...[more]

PMID: 33458326

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Project description:Background and purposeA recent study of NSCLC patients showed small residual setup errors (shifts) in the direction of the heart following image-guidance were significantly related to overall survival. This study of the dosimetric effects of these residual shifts investigates the hypothesis that observed survival differences were related to a change in heart dose.Materials and methodsAccumulated doses including shifts for each fraction were determined for 475 NSCLC patients. Planning CTs and corresponding dose distributions were deformed to a reference. Image-based data-mining techniques were then applied to the difference between the planned and accumulated dose (Δdose) to determine where Δdose relates to 1-year survival. The significance of Δdose in the identified region was assessed using multivariable Cox analysis. The cohort was then split into octiles, based upon planned dose to the region, and multivariable Cox analysis performed for each sub-cohort to explore the dose response relationship. The identified dose threshold for damage was then tested in an independent validation cohort of 1482 NSCLC patients from the same institution.ResultsPermutation testing identified a small region in the heart base where Δdose significantly correlated with 1-year survival. Δdose in this region showed no correlation with common clinical variables, and was significant in multivariable Cox regression (p < 0.001, hazard ratio 1.221/Gy), with increasing change in dose from plan resulting in greater risk of death. Octile analysis revealed Δdose to be significant only in the 7th octile, planning dose 16.2-23.4 Gy, suggesting a steep dose-effect relation for heart damage in this range. Taking 16.2 Gy as a conservative threshold dose, this result was successfully validated, with a significant difference being seen between patients with a region dose above or below 16.2 Gy.ConclusionsThis study suggests the relation between residual set-up errors and survival is explained by changes in cardiac dose, and identifies an area at the heart base where dose is correlated with survival. Our results suggest the dose threshold for cardiac damage is between 16.2 and 23.4 Gy in the base of the heart, which was validated in an independent cohort. However, the dose effect in other regions of the heart should also be investigated.

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Dataset Information

Dose surface maps of the heart can identify regions associated with worse survival for lung cancer patients treated with radiotherapy.

Background and purpose

Material and methods

Results

Conclusions

Publications

Dose surface maps of the heart can identify regions associated with worse survival for lung cancer patients treated with radiotherapy.

Similar Datasets

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