Evaluation of Radiotherapy Boost in Women with HER-2 positive Breast Cancer

Previous randomized controlled trials have proven similar local recurrence and survival rates in patients with early breast cancer treated with either breast conservative therapy (including Whole Breast IrradiationI) or mastectomy (i.e: the removal of one or both breasts) (Fisher et al., 2002; Litiere et al., 2012). Patients treated with breast conserving surgery often receive a radiation dose boost to the tumor bed in order to prevent tumor recurrence in its original site, since local recurrence mostly happens at the site of the primary tumor harbouring remaining microscopic tumor cells. Previous studies show improvement in local control for patients treated with radiation therapy boost as compared to those with no boost (Bartelink et al., 2007; Bartelink et al., 2015). As such, the National Comprehensive Cancer Network (NCCN) and European guidelines recommend using a radiation therapy boost in patients with high risk of cancer recurrence (Gradishar et al., 2018; Senkus et al., 2015).
However, it remains unclear whether these findings are applicable to HER-2 positive patients in the current era (with advances in chemotherapy, immunotherapy and surgical techniques). HER-2 is the Human Epidermal growth factor, a human protein that can affect the growth of breast cancer cells.
In this context, radiation oncologists need more information about the effect of radiation therapy in this population, to carefully balance the local control benefit of RT boost with its potential side effects.
To date, there are no large studies evaluating the benefit of RT boost in patients with HER-2 positive breast cancer.
We aim at evaluating the effect of RT boost on loco-regional recurrence, any recurrence, overall survival, disease-free survival and distant metastasis-free survival in patients with HER-2 positive breast cancer.