I'm going to go with Christine on no port for "only radiation" since David's example speak more to reasons for getting a feeding tube. Of course, if you don't get a feeding tube, then a port may be helpful.
This will be my third round of radiation and I have never needed an IV any of those times for anything connected to radiation, only the chemo.
The chemo does require IV to get and that's where a port could be handy. Weight loss is addressed by a feeding tube except for those who need parental infusion thru the veins - very rare so no need for a port there. Dehydration is easy enough with water in the feeding tube or even a nasal tube. Same goes for malnutrition. Nausea may be helped by an IV
Heck even this time around, I'm passing on a port despite getting chemo. My veins have fully recovered. Ports are not problem free and I don't see the potential benefit outweighing the very real routine risks (pain, bruising, or swelling plus infection and bleeding)/ Plus with my luck I would get one of the more serious but very rare Potential complications of a port internal bleeding, nerve damage,collapsed lung, fluid build up around the lungs, blood clot formation, and accidental cutting or puncturing of blood vessels.) Heck I already am in the 5% minority for whom Erbitux does not work and the complication rate is about 10% for ports.