Hi. Thanks for the query.. As per your complain mouth dryness along with blood in sputum with a history of radiation therapy and repeated linear therapy seems to be due to damage to the salivary glands caused by radiation leading to reduced function of salivary gland and also causing dry mouth.. Blood in saliva can be due to inflammation inside the mouth along with inflamed gums that is one of the most common casuse for blood in sputum.. However blood can also be coming from throat or upper G.I tract and you need to get a thorough clinical examination done to rule out the cause for blood in sputum.. As of now for dry mouth you can start chewing sugar free chewing gums, suck tart candies and drink plenty of water.. You can use specialised mouthwash like Biotene that contains methyl cellulose and is suitable for dry mouth patients.. You can also instil artificial saliva drops.. Do warm saline gargles.. Chew a Vitamin C pellet daily as it aids in immunity.. Hope this helps.. Regards.