my cat has been diagnosed as having lung cancer - possible secondaries. he was treated with antibiotics and steriod injection and is now seemingly full of life except for his laboured breathing. he is eating, has put on weight and is in fine purring form. He has been 'snoring' for years but it is only in the last year that his breathing has become more audible. since antibiotics his cough has lessened noticeable. Without any further treatment, how long could i expect him to live? He is 8.