Worldwide, breast cancer is the most commonly diagnosed female malignancy and the leading cause of cancer mortality in women.1,2 Radiotherapy (RT) is an essential component of multimodal breast cancer treatment. Adjuvant irradiation to the residual breast after wide local excision of the primary tumor provides equivalent outcomes to mastectomy while ensuring superior cosmesis.3,4,5 In patients with risk factors after mastectomy, adjuvant radiotherapy improves overall survival and local control.6,7 Due to improvements in breast cancer treatment, the number of long-term survivors has increased over the past decades.8 With larger numbers surviving, more patients become at risk of developing a wide range of late radiation-related side effects. Postoperative radiotherapy in patients with left-sided breast cancer is characterized by exposure of significant portion of the heart volume to high doses of irradiation.9 Pathophysiology of radiotherapy-induced cardiac toxicity involves damage of blood vessels and interstitial fibrosis, leading to coronary artery disease, valvular abnormalities, myocardial dysfunction, pericardial disease and conductive disturbances. These changes can become clinically manifest several years or even decades after treatment, leading to increased risk for cardiac morbidity and death.10,11,12,13,14,15,16,17,18,19,20,21,22,23,24 The increased risk is proportional to the dose received by the heart, begins within years after exposure and continues for decades.12 Various radiotherapy techniques, including breath hold (BH) during treatment have been proposed to reduce the cardiac dose.25,26 It is expected that these maneuvers will result in reduced probability of late clinical manifestations of cardiac events.12,27,28 Voluntary deep inspiration breath hold (V-DIBH) radiotherapy has been studied in the setting of breast conserving treatment and post-mastectomy.25,26 Using this technique, the distance from the chest wall to the heart increases during deep inspiration, resulting in a decrease of cardiac volume in the radiotherapy field. While consistency and stability of V-DIBH has been demonstrated, real-time positional monitoring is advocated in daily practice to apply corrective actions due to intra-fractional movements.29,30 In 2015, we implemented V-DIBH for patients undergoing leftsided breast cancer radiotherapy, based on a prospective observational study protocol. This implementation in routine practice was based on the existent body of evidence in favor of V-DIBH.25,26 We aimed to ensure controlled transition to the new routine technique and to report on feasibility of this approach in our clinical setting and its dosimetric impact. Our hypothesis was that V-DIBH, when compared with free-breathing (FB) technique, will result in statistically significant reduction of the commonly reported cardiac dose-volume histogram (DVH) parameters without compromising the coverage of the target volume with prescribed dose. We also hypothesized that V-DIBH treatment results in non-inferior set-up accuracy when compared with FB. Our study was approved by the institutional Medical Research Center (Study No. 15330/15), on 14. 10. 2015 by the Hamad Medical Corporation Medical Research Centre.
Table 1Vertical, longitudinal and lateral couch shifts and corresponding systematic and random errors for the initial 18 patients treated with voluntary deep inspiration breath-hold (V-DIBH) and a historic control treated with free-breathing (FB) technique. Differences between the two approaches were non-significant.
When compared with free-breathing radiotherapy, voluntary deep inspiration breath-hold enabled significant reduction of cardiac doses without compromising the target volume coverage in our cohort of left-sided breast cancer patients. Treatment setup shifts and population systematic and random errors were small and not significantly different from the historic controls treated with the free-breathing technique. Our systematic approach to patient coaching was reflected in low rate of conversion to free-breathing radiotherapy. Based on the positive results of our present study and experience gained, we adopted V-DIBH radiotherapy as standard treatment for all left-sided breast cancer patients. Long follow up is needed to confirm the clinical impact of the presented favorable dosimetric benefit. 153554b96e