Heart Sparing Radiotherapy Techniques in Breast Cancer: A Focus on Deep Inspiration Breath Hold

Abstract

Adjuvant radiation therapy is a critical component of breast cancer management. However, when breast cancer patients receive incidental radiation to the heart, there is an increased risk of cardiac disease and mortality. This is most common for patients with left-sided breast cancers and those receiving nodal irradiation as part of treatment. The overall risk of cardiac toxicity increases 4-16% with each Gray increase in mean heart radiation dose, with data suggesting that no lower limit exists which would eliminate cardiac risk entirely. Radiation techniques have improved over time, leading to lower cardiac radiation exposure than in the past. This decline is expected to reduce the incidence of radiation-induced heart dysfunction in patients. Deep inspiration breath hold (DIBH) is one such technique that was developed to reduce the risk of cardiac death and coronary events. DIBH is a non-invasive approach that capitalizes on the natural physiology of the respiratory cycle to increase the distance between the heart and the therapeutic target throughout the course of radiation therapy. DIBH has been shown to decrease the mean incidental radiation doses to the heart and left anterior descending coronary artery by approximately 20-70%. In this review, we summarize different techniques for DIBH and discuss recent data on this technique.

Keywords: active breathing control; breast cancer; deep inspiration breath hold; heart; radiation; real-time position management.

Figure 1

Cardiac position and proximity to the left breast target volume for a patient simulated in both free-breathing and DIBH positions. Position of the heart in free-breathing (A), demonstrating the proximity of the heart to the left breast and nodal target volume. Position of the heart in DIBH (B), demonstrating that the heart is positioned further away from the target volume. When the free-breathing (purple) and DIBH (green) images are fused based on the left breast target volume, the significant difference in cardiac position in the axial (C) and sagittal (D) planes can be appreciated. The position of the heart is contoured in white (solid white, DIBH; dashed white, FB). With DIBH, the heart is displaced inferiorly and medially, further away from the left lateral chest wall.

Figure 2

Axial sections with isodose lines for a patient planned for left chestwall and regional nodal treatment (including the internal mammary chain lymph nodes) using four different techniques. (A) Free breathing (FB) 3DCRT, (B) DIBH 3DCRT, (C) FB VMAT, (D) DIBH VMAT.

Figure 3

Dosimetric comparison for the heart and left lung, using free-breathing (FB) 3DCRT, DIBH 3DCRT, FB VMAT and DIBH VMAT for the patient shown in Figure 2. (A) Comparison of dose to PTV (cyan), left lung (green), and heart (red) for FB 3DCRT (closed circles) and DIBH 3DCRT (open circles). (B) Comparison of dose to PTV (cyan), left lung (green), and heart (red) for FB VMAT (triangles) and DIBH VMAT (squares). (C) DVH for the heart with all four planning techniques: FB 3DCRT (closed circles), DIBH 3DCRT (open circles), FB VMAT (triangles), and DIBH VMAT (squares). (D) DVH for the left lung with all four planning techniques: FB 3DCRT (closed circles), DIBH 3DCRT (open circles), FB VMAT (triangles), and DIBH VMAT (squares). (E) DVH for the left anterior descending coronary artery (LAD) with all four planning techniques: FB 3DCRT (closed circles), DIBH 3DCRT (open circles), FB VMAT (squares), and DIBH VMAT (triangles). (F) Comparison of doses to the heart, left lung, and LAD with FB 3DCRT, DIBH 3DCRT, FB VMAT, and DIBH VMAT plans. Note in this patient that DIBH vs FB reduced the percentage of higher doses received by the left lung, heart, and LAD, and that DIBH VMAT showed greater reductions than DIBH 3DCRT and FB VMAT.