Oligometastatic breast cancer: old to new entity, outcome and treatment algorithm

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Published: 31 Jan 2023
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Prof Sandra Swain - Georgetown University Medical Center, Washington DC, USA

Prof Sandra Swain speaks to ecancer at BGICC 2023 about oligometastatic breast cancer.

She defines the term oligometastatic as the intermediate step between primary breast cancer and metastatic breast cancer and then highlights the theoretical approaches which surround this term.

Prof Swain also outlines key randomised breast cancer studies presented in her BGICC 2023 talk such as the ongoing OLIGOMA trial.

The first talk I gave was about oligometastatic breast cancer and it’s interesting because I really didn’t even know what it was; you hear that term all the time. So, I really dug into the literature about it and it was really defined by Hellman and Weichselbaum in 1995 in The Journal of Clinical Oncology where they gave it that name – oligometastatic disease. It was really based on the fact that it was an intermediate step between primary breast cancer and metastatic breast cancer. The old theory was that all breast cancer was systemic, by Fisher, but their theory is that there is an intermediate stage that you can affect survival if you treat it with local therapy. 

So there have been a lot of retrospective studies looking at using local therapy with radiation – surgical radiotherapy, basically. What these studies showed was that there was a hint that maybe there was a benefit if you give radiotherapy to a limited number of metastatic sites. 

Now, oligometastatic disease has been defined many times as five lesions or less and it can be in any organs. If you look at the recent data from the Netherlands, it’s probably more likely three lesions or less is where you have a survival cut-off. In other words, if there are three lesions or less those patients with breast cancer did better than if they had more. So that is the group you probably can affect the most.

So I presented a couple of randomised studies, one the NRG did, and I’m in that group, where we compared using systemic therapy with radiotherapy to the metastatic sites versus just systemic therapy alone. We did not find a benefit of adding the radiotherapy, the SBRT. So that was a negative trial so we didn’t go on to the phase III. Now, there was another trial that I talked about from Memorial Sloan Kettering where they looked at just asymptomatic bone metastasis in breast cancer and randomised patients again to radiation therapy to the sites of metastatic disease, and it was five or less, versus not radiating and the endpoint was skeletal related events. Their study was a positive study – there were less skeletal related events in those patients who got the radiation to these asymptomatic bone mets and there was also a survival benefit. 

Now, the caveats for that study – it’s a small study and it’s a phase II, so that’s limited data. The other thing was only about half of the patients on either arm got bisphosphonate therapy. We all know bisphosphonates are recommended in patients who have bone mets so that was not following standard of care. So the question is, if all the patients had gotten bisphosphonates would there really have been the outcome that they saw, would there have been a positive outcome? We don’t really know that. So, more work would need to be done before I would say that patients should have radiation to their asymptomatic bone mets based on that study alone. You need more data than that. 

Now, there is a large study called the OLIGOMA study with over 500 patients that is in process right now. Again, randomising patients to get systemic therapy plus radiation versus radiation to patients who have five or less metastases. So, as you can see from how I’m talking, there’s no definitive answer on this right now. I would say it’s not standard of care to do radiation, SBRT or whatever you call it, radiosurgery, to these sites, these limited sites, right now. I think the systemic therapy is the most important aspect for these patients.