Dear query: RFA is generally appropriate if the liver metastases are the primary problem. In most cases of breast cancer, this means that there is no other systemic disease. The reason for this is that RFA is a local treatment only. It makes no sense to go through this procedure if there is extensive disease outside the liver because the RFA will not address that disease. So, in the case you illustrate, it sounds like the bone mets are the primary problem. The 2-3 liver mets will not cause big problems in terms of organ function, so using RFA is just an extra procedure that does not address the total problem. Chemotherapy would, technically, address both problems. In the ideal situation, 1-2 liver mets (located appropriately) with NO other disease, RFA would address this well without the toxicity of systemic chemotherapy.
The role of RFA in cancer treatment is not yet well-established; some studies have shown, in some cases, "survival benefit," which means living measurably longer. That can be weeks or months; it's not really about cure. So it has tended to be used either for primary liver cancer (cancer that starts in the liver) when surgical removal is not an option, or for metastatic liver tumors. When there are "isolated" liver mets, it is presumed that in fact the likelihood of more mets which are undetectable is high; so it would be an extremely rare situation in which the treatment would afford cure. In the case of known mets elsewhere, then the reason to consider RFA would be if some symptom or other might be better controlled in that way than in others. It's hard to think of such a situation: obstructive jaundice, for example, would likely be treated more durably with a stent. And being unable to treat the bone mets, in your specific example, would mean continuation of the problems from that situation, unabated. As to chemo vs RFA: if RFA were able to find and treat every metastatic focus, it would theoretically be a good thing, in that it would avoid side effects of chemo (altho, in placing needles through various organs it carries its own risks); that is not the case, however. Chemo, by getting into the bloodstream, goes everywhere there might be tumor (except, sometimes, it may not cross into the brain) which makes it a better "hunter." The perfect treatment of metastatic disease does not exist: one that kills all cancer cells and does no harm to normal cells. That is the focus of most cancer research; there are signs of progress.