Lower Lobe Removal

In July, 2014 I had my lower left lobe removed when a suspicious spot, too small to biopsy, was removed and determined to be Stage 1A Cancer. Since that time, I find that I get out of breath much earlier than before and have attributed this to my decreased lung capacity. I have had all of my medical procedures and surgery done at the VA because my cancer was determined to be service connected. The doctors at VA tell me that the decreased lung size should have nothing to do with the fact that I easily get out of breath. Is this correct? PS: I get scanned twice a year and so far I am cancer free!