Combined trastuzumab and radiation therapy for HER2-positive uterine serous carcinoma: A case report.

Overexpression of HER2 in endometrial cancer is associated with poor prognosis, aggressive disease, and resistance to standard therapies. Recent studies have shown that HER2-targeted therapies, such as trastuzumab, can be effective in treating HER2-positive endometrial cancer in combination with chemotherapy. Currently, the management of advanced-stage HER2-positive uterine serous carcinoma (USC) consists of adjuvant platinum-based chemotherapy with concurrent trastuzumab followed by trastuzumab maintenance therapy until disease recurrence or prohibitive toxicity. In the setting of persistent pelvic disease following systemic therapy, consolidation with tumor-directed radiation therapy also offers an opportunity to eradicate residual disease. With the emergence of molecular tumor classifications and systemic therapies (chemotherapy, immunotherapy, and target therapies), the landscape of adjuvant multi-modality therapy is ever changing and increasingly individualized. Currently, there is no prospective evidence to guide pelvic radiotherapy with concurrent trastuzumab in endometrial cancer, and as a result, no reported toxicity in endometrial cancer patients. In this case report, we present two patients with HER2-positive USC who received multi-agent chemotherapy with trastuzumab followed by pelvic radiation therapy and concurrent trastuzumab. Both patients tolerated this multimodal treatment without significant or persistent moderate or severe adverse events. These two cases provide insight into the safety and feasibility of administering radiation therapy with trastuzumab in endometrial cancer in the maintenance phase. Our report suggests that trastuzumab-based therapy may be a promising treatment option for HER2-positive endometrial cancer patients who receive concurrent or adjuvant chemotherapy and radiation therapy.