How would you treat a young breast cancer patient with limited nodal involvement and an isolated sternal oligometastasis at diagnosis?

Although there is limited data to support this approach, I have treated similar patients with "curative intent" with respect to the RT portion of their treatment.

If the sternal oligomet is in close proximity to the ipsilateral IMNs, it can be included within the partial wide tangent fields for the ...

Agree with the approach of Dr @Dr. First Last. In appropriately selected and motivated patients, definitive intent therapy (as suggested above) can be considered. Here is an example of a single institutional experience regarding such a scenario.

Christopherson et al., PMID 30851348

This should probab...

A "sternal oligometastasis" is probably not a true oligometastasis but rather internal nodal involvement and as such has a better prognosis than the usual oligometastasis. I favor reasonably aggressive local regional treatment preferably with concurrent chemotherapy, e.g.capecitabine.