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  4. Normal Tissue Dose Estimation Error for Breast EBRT Patients Due to the Calculation Algorithm Differences

Normal Tissue Dose Estimation Error for Breast EBRT Patients Due to the Calculation Algorithm Differences

C Lee1*, R Golduber1 , M Mille2 , J Jung3 , A Berrington de Gonzalez2 , C Lee2 , (1) University of Michigan, Ann Arbor, MI, (2) National Cancer Institute, Bethesda, MD, (3) East Carolina Univ, Greenville, NC

Presentations

(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: To see if there is any systematic dose estimation difference between two commercial photon dose calculation algorithms, AAA and AcurosXB, with regard to the doses to heart, esophagus, and ipsilateral lung under the external beam breast RT for their implication to the epidemiological studies.

Methods: Total of 20 left and 33 right breast patients were retrospectively investigated for their normal tissue dose using the Eclipse treatment planning system (Varian Medical System, Palo Alto, CA). The clinical planning doses calculated by the AAA algorithm were compared to the AcurosXB calculations. For patients who received electron boost, Varian’s eMC dose calculations were added to the total dose. Mean dose to heart, V20Gy(cc) of the lung, and mean dose to esophagus were compared.

Results: On average, the mean heart doses calculated by AcurosXB were lower by 5.3%(Std Dev 3.2%) than AAA for the left breast treatments, while they were 25.4% (Std Dev 14.3%) higher for the right breast treatments. Esophagus dose estimated by the two algorithm also showed similar trends (8.3% lower for left breast treatments and 9.5% higher for right breast treatments by AcurosXB as compared to those by AAA). However, V20Gy(cc) of ipsilateral lung did not show significant difference between two algorithms.

Conclusion: Estimation of the normal tissue dose from the breast external beam radiation therapy can be affected by the choice of dose calculation algorithm. The use of more advanced algorithms, such as AcurosXB, may provide more accurate dose estimation due to its superior performance over the very heterogeneous medium. Long term follow-up studies of radiation late-effect should consider using more advanced dose calculation algorithms, such as AcurosXB or Monte Carlo codes.

Funding Support, Disclosures, and Conflict of Interest: This work is funded in part by SubK-NIH-DHHS-US through a consortium with Social & Scientific Systems- PHR-SSS-P-17-005269

Keywords

Breast, Heart, Dosimetry

Taxonomy

TH- External beam- photons: out of field dosimetry/risk analysis

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