Is there a role for anti PD-1/checkpoint inhibitors or other immunotherapies with radiation?

There's a lot of enthusiasm, and fairly little evidence so far.  Driving the interest is the observation made over the past several decades, that radiation can induce an immunologic/abscopal response:  that by treating one site of disease, a systemic response is initiated that results in responses in non-radiated sites.  This has been the subject of numerous case reports in patients treated with radiation alone.  Recently there have been case reports of a similar phenomenon in patients receiving immune checkpoint inhibitors (in NSCLC, or melanoma) and laboratory experiments that support it.  But its not known how rare or common this might be.  

The downside is that activation of the PD1/PDL1 pathway can result in autoimmune events, including pneumonitis, so there is a concern that combination therapy may not be safe.  As experience (mostly unpublished) has accumulated, this concern has diminished somewhat. 

For now, many clinical trials are ongoing.  Off protocol, I frequently offer radiation to patients receiving or who have received various immune checkpoint inhibitors - proceeding with caution, and the appropriate informed consent.