Xray thoracic/lumbar spine.

This is a reasonable choice. Possibly Hip/Pelvis xray can be added as well. Xrays can show if there are any bony lesions that are suspicious for bony metastases, as well as pathologic fractures.

You decide though, that you want to prevent Emil from having to go for more tests than absolutely needed at this point to save him some grief.

Try something else now that may be even more informative for you and is readily available.