targeted radiation for stage IV NSC lung cancer

Hi all - trying to help my mother-in-law. She was diagnosed with non-small cell adenocarcimona lung cancer in June 2010 with 2.7 cm nodule in one lung and 1.4 cm nodule in other lung and 6 of 9 lymph nodes positive. No cancer anywhere else. She did 6 rounds of cisplatin and avastin. Latest PET scan and CT scan shows rt lung nodule is dark while left side still active along with new lymph node. No cancer anywhere else.

Radiation oncologist says to wait for radiaiton until she needs it as they can only do it once. Does that make sense? She would rather have radiation now so she has more quality time rather than wait until she's really bad. I think that makes sense.

For those of you going through this, what are your thoughts? Thanks, Traci