In-vivo dosimetry comparison of supraclavicular junction dose for breast and chest-wall patients with and without deep inspiration breath hold (DIBH)

Purpose: The use of deep inspiration breath-hold (DIBH) for patients with left-sided breast cancer reduces cardiac dose, with the aim of reducing the risk of major coronary events. However, this technique has not been universally adopted for patients requiring regional nodal irradiation (RNI) with one concern related to the junction dose. This study evaluates the dose received at the junction for both DIBH and free-breathing patients having tangential breast/chest wall radiation and regional nodal radiation treated with 3D-conformal or hybrid IMRT radiotherapy. Methods: In-vivo dosimetry measurements utilizing EBT3 GafChromic (TM) film were performed for 19 patients during three fractions over their course of treatment. The mean junction dose and variability in junction dose were compared between the DIBH and free breathing patients. Results: Our results show that for voluntary DIBH (v-DIBH) patients the junction dose is more variable between fractions. However, when comparing the average junction dose for DIBH and free breathing patients over the three measurements, the difference was small and not statistically significant. A larger difference was seen when patient measurements were analysed based on treatment linac. Conclusions: These results show that the mean junction dose is not significantly compromised by the use of v-DIBH. The small possibility of a change in junction dose due to breathing technique should be weighed against the proven increased risks associated with excess cardiac dose received by free-breathing patients. If junction dose is of concern, an in-vivo study, such as this one, could allow cautious introduction of DIBH for patients requiring supraclavicular irradiation.