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  4. Dosimetric Comparison of Supine and Prone Techniques for Left Breast Radiation Treatment Using Radialogica

Dosimetric Comparison of Supine and Prone Techniques for Left Breast Radiation Treatment Using Radialogica

N Novakowski1*, L Kumaraswamy1,2, IZ Wang1,2, (1) University at Buffalo (SUNY), (2) Roswell Park Cancer Institute, Buffalo, NY

Presentations

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

Room: Exhibit Hall

Purpose: Whole breast radiation following lumpectomy has been proven to be as effective as mastectomy for early stage breast cancer. Potential risks associated with breast radiation include complications to the organs-at-risk (OARs). Besides lungs, heart is especially of concern for left breast radiation. Dosimetric indices collected from Radialogica fullAccessᵀᴹ software provide the ability of a direct comparison of three different breast radiotherapy techniques, i.e., breath hold supine, free breathing supine, and prone breast radiation.

Methods: Treatment plans for 65 early stage left breast patients were exported from Eclipseᵀᴹ treatment planning system and uploaded to fullAccessᵀᴹ. Of these 65 patients, 18 were treated with free breathing supine, 26 utilized breath hold technique, and 21 were treated with prone breast radiation. Dosimetric data collected from fullAccessᵀᴹ were analyzed and compared among the three groups. The main dosimetric parameters studied were CTV D100%, body Dmax, V20Gy left lung, V25Gy heart, and DMean heart.

Results: For prone patients, all dosimetric constraints were met within the preset tolerance in fullAccessᵀᴹ template. Eleven supine patients (3 breath hold and 8 free breathing) had at least one parameter outside of tolerance. For free breathing, breath hold, and prone breast radiation: mean±SD for CTV relative D100% was 97.8±1.7%, 97.2±2.4%, 100±1.9%; body Dmax was 110.2±2.7%, 108.2±2.2%, 106.0±1.1%; V20Gy left lung was 12.2±10.5Gy, 11.1±1.9Gy, 0.3±0.8Gy; V25Gy heart was 3.5±3.3Gy, 0.2±0.4Gy, 0.01±0.03Gy; and DMean heart was 3.6±3.1Gy, 1.1±0.2Gy, 1.1±0.2Gy, respectively.

Conclusion: Using data from Radialogica fullAccessᵀᴹ, the retrospective study showed prone breast radiation as a superior technique to conventional supine techniques for CTV coverage, dose uniformity and OAR sparing in left breast radiotherapy. While breath hold supine technique showed better heart sparing than free breathing, difference in left lung doses was not significant between the two. Clinical effectiveness and complications are to be further studied for correlation with these dosimetric differences.

Keywords

Dosimetry, Breast

Taxonomy

TH- External beam- photons: treatment planning/virtual clinical studies

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