Primary bone cancer and secondary lung cancer

My father (78 years old) has been diagnosed with both bone cancer and bilateral lung cancer, he has lost a signifanct amount of weight and has been told that there will be no surgical intervention possible radiotherapy to shrink the mass on his back and relieve symptoms .  The consultant said he has months but I want to know how many and whether radiotherapy will give him more time.  He has sarcoma which is aggressive I believe.