Abstract ES7-3: Indications for radiation treatments after neoadjuvant chemotherapy while awaiting the results of clinical trials

Using systemic therapy prior to surgery has become an accepted standard for patients with lymph node-positive disease at presentation. Studies demonstrate that this approach can eradicate the disease in lymph nodes prior to local-regional interventions. This occurs particularly frequently for patients with HER2/neu-positive disease and to a relevant degree for those with triple negative disease. Patients with an excellent pathological response to treatment have improved outcomes compared to those with extensive residual disease. However, it is less clear whether local-regional therapies can be diminished or omitted in patients with an excellent pathological response. Accordingly, such questions are currently being investigated in phase III clinical trials. Unfortunately, local-regional therapeutic trials require long-term outcome data, particularly for the endpoints of distant disease control and overall survival. Therefore, the ongoing studies addressing whether regional lymph node radiation can be omitted in selected patients after neoadjuvant chemotherapy will not provide clinically useful information in the near term. This is unfortunate because such questions arise with a high degree of frequency in oncology practices. This topic has also become increasingly important because completed clinical trials indicate that regional lymph node radiation combined with treatment of the chest wall/breast improves the outcome of patients with pathologically positive lymph node(s) and who are treated with surgery first followed by adjuvant systemic therapy. While the sequencing of chemotherapy and surgery does not affect the risk of local-regional recurrence for populations of patients, it does affect an individual patient9s risk. For example, patients with clinically stage II, lymph node-positive disease (who do not receive radiation) will have lower risk of local-regional recurrence if they achieve a pathological complete response to neoadjuvant chemotherapy compared to those with residual positive lymph nodes. This is also true for patients with clinical stage III disease, although patients with locally advance breast cancer have a high enough risk for local recurrence even with a complete pathological response to warrant adjuvant radiation. Based on the data outlined above, the current standard outside the setting of clinical protocols is to recommend regional lymph node radiation with chest wall/breast radiation for all patients with residual positive lymph nodes after neoadjuvant chemotherapy and all patients who present with clinically stage III disease. For patients with stage II disease who achieve a pathological complete response, the available evidence suggests that their predicted local regional recurrence risk without regional or postmastectomy radiation is 10% or less. Therefore the benefit from radiation is likely low and it is reasonable weigh out these small potential benefits in the context of associated treatment morbidities and costs. It is also important to further consider additional local-regional risk factors such as patient age, tumor biology, plans for prolonged systemic therapies, and other pathological factors at presentation in making radiation treatment decisions for such patients. Citation Format: Buchholz T. Indications for radiation treatments after neoadjuvant chemotherapy while awaiting the results of clinical trials [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr ES7-3.