Including internal mammary lymph nodes in radiation therapy for synchronous bilateral breast cancer: an international survey of treatment technique and clinical priorities.

PURPOSE: The aim of this study was to understand the international standard practice for radiation therapy treatment techniques and clinical priorities for institutions including the internal mammary lymph nodes (IMLNs) in the target volume for patients with synchronous bilateral breast cancer.

METHODS: An international survey was developed to include questions that would provide awareness of favored treatment techniques, treatment planning and delivery resource requirements, and the clinical priorities that may lead to the utilization of preferred treatment techniques.

RESULTS: Of the 135 respondents, 82 indicated that IMLNs are regularly included in the target volume for radiation therapy (IMLN-inclusion) when the patient is otherwise generally indicated for regional nodal irradiation. Of the 82 respondents that regularly include IMLNs, five were removed as those respondents do not treat this population synchronously. Of the 77 respondents, institutional standard of care varied significantly, though VMAT (34%) and combined static photon and electron fields (21%) were the most commonly utilized techniques. Respondents did preferentially select target volume coverage (70%) as the most important clinical priority, followed by normal tissue sparing (25%).

CONCLUSION: The results of the survey indicate that the IMLN-inclusion for radiation therapy has not yet been comprehensively adopted. As well, no consensus on best practice for radiation therapy treatment techniques has been reached.