For a young patient with high grade pT1N0 medially located breast cancer, under what circumstances would you include the IMN in your treatment fields?

For patients treated with upfront surgery who are T1N0, I personally do not radiate the lymph nodes, even in young patients with high grade lesions. An exception could be in patients with extensive LVI where the likelihood of nodal involvement is higher. For patients with initially more advanced disease who are node positive and convert to node negative, then yes I would treat the internal mammary, undissected axilla, and supraclavicular regions, or enroll them on NRG B51 where they would be randomized to treat nodes (including IMN) or not.

In the upfront surgery situation, despite the fact that the randomized European trial (EORTC 22922; Poortmans et al., PMID 26200978) did include medial node negative patients and there may be a potential...