Is it appropriate to treat unresectable secretory insulinoma of tail of the pancreas with radiation therapy?

Absolutely, it is the preferred treatment. Well differentiated functional NETs of the pancreas have been considered a resistant histology. However, the available data are based on palliative doses (BED<50Gy). It is an open question, but very likely that ablative doses (BED>100Gy) can overcome this resistance.

Either approach will almost always lead the tumor to stop functioning, which is a profound clinical benefit.

The DM rate is high and the natural history is typically indolent, so treating...