Pallitive Radiation treatment for 78 yr old

Hi, last Jan. my 78 yr old mom, who had been doing OK on oxygen therapy (10yrs) for COPD, was diagnosed with lung ca (no symptoms at that time - was found accidently). They couldn't do a biopsy because her sats went too low (below 90) when she was laid flat. They of course couldn't do surgery either. She is too fragile for chemo but the dr did offer pallitive radiation treatments for her when she starts to have trouble breathing. She's had regular follow-ups (every 6 weeks) with X-rays each time to chart the growth of the tumor. She lives in a nursing home, and is fairly weak and fragile - sleeps several hours a day. The last X-ray and check up has come with increased trouble breathing with movement (walking to washroom, getting in and out of bed) - the dr noted there is increased fluid build up and noted it could be drained. He also suggested it would be a good time to consider the radiation treatment. The oncologist has said it would consist of 10 treatments - 5 days a week for 2 wks. The side effects he noted is tiredness, nausea that would last during the 2 wks and probably about 1 wk after treatment. He would prefer that she have her lung drained first.
My brother and I are concerned that she might be too weak for that much radiation treatment - we thought that palliative radiaiton would only be 1 or 2 treatments not 10. The dr doesn't seem too concerned about that and still is recommending it. The other factor is that the treatments would be happening in a city 2hrs outside of where she currently lives (my brother does live in that city) and would likely have to find her a nursing home that would take her on a 2-3 week short stay as she's not capable of staying by herself and they do not hospitalize for this treatment. Even her family dr said to go for it but when I asked him how long it would be he thought it would only be 2-3 treatments - he didn't realize it was 10 treatments either.
What should we consider before we decide if the radiation is the right thing to do? or even the lung draining. Wouldn't the lung draining procedure be difficult for her too? How low before before fluid builds up again?