RESEARCH – September 2021

Dose evaluation of the left anterior descending coronary artery (LAD) in left breast cancer patients treated with deep inspiration breath hold (DIBH) and free breathing

Authors: Rena Tiigi, Anni Borkvel, Merve Adamson, Kati Kolk, Kätlin Tiigi

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Breast cancer has the highest incidence among women in Estonia and all over the world, while the incidence is rising every year. Possible treatment modalities for breast cancer are surgical treatment, systemic therapy and radiation therapy. Systemic and radiation therapies can increase the risk of heart disease and cause cardiac toxicity, which is dependent on the drug and breast side (left or right). Radiotherapy can cause late toxicity such as constrictive pericarditis, arrhythmias, restrictive cardiomyopathy and can be particularly damaging to coronary arteries, mainly to left anterior descending coronary artery (LAD). Reducing the risk of late toxicity is essential in terms of long survival of breast cancer patients.

Deep inspiration breath hold (DIBH) is one of the contemporary breast radiotherapy techniques, which can significantly reduce the dose for heart. It involves delivery of radiation during maximum DIBH. Heart and LAD can almost entirely be removed from the tangential treatment field during DIBH.

Reduction in the LAD dose was studied in 20 left-side breast cancer patients with a mean age of 55 years. All patients underwent breast conserving surgery and were prescribed a 50 Gy total dose in 25 fractions. Ten of the 20 patients also received systematic treatment, 8 patients received chemotherapy with anthracyclines and 2 patients with taxanes and carboplatin. Among the10 chemotherapy patients, 3 patients received traztuzumab.

Two computed tomography scans were taken, one with free breathing and one with deep inspiration breath hold. Heart, LAD and lung were defined as the organs at risk and planning target volume (PTV) was defined according to the ESTRO guidelines (14). Two different treatment plans were designed for each patient, one with free breathing and one with DIBH. The treatment plan involving free breathing was only developed for the study purpose, all patients received DIBH radiotherapy. Maximum dose (Dmax) for LAD and mean dose (Dmean) for heart in grays (Gy) were compared.

Both plans provided equally good coverage for the PTV (p=0.3568), respiratory gated radiotherapy reduced maximum dose for LAD by 2.6 times (p=0.0001) and mean dose for heart by 1.8 times (p=0.0001).