Are there circumstances where you would use hemibody irradiation?  

I have used hemibody radiation with some regularity for widely metastatic disease, particularly for relatively radiosensitive solid tumors such as breast and prostate, and have found it particularly helpful for multiple myeloma where it can and often does work wonders for pain relief. In additi...

Hemibody RT remains a reasonable option for patients with widespread painful metastases and very limited life expectancy. RTOG 7810 established efficacy, safety, and dosing: 8 Gy x 1 lower, or 6 Gy x 1 upper. Premedicate with steroids and zofran. Nicely reviewed here. 

I usually try radioisotopes in that setting. Ra223 is approved for prostate and under trials for breast, but older agents like Samarium too.