Hi! My dad has stage 4 colon cancer diagnosed in oct 2010. He has been on chemo. every 2 weeks since Nov. 2010. He has noticed shortness of breath after his treatments. Initally he was on FOLFOX(oxcaliplatin) and 5FU as well as Avastin. All of the drugs have shortness of breath as their side effects. His oxygen saturation was measured several times with each of his complaints and it was 100% each time. They don't say anything much about it. Another reason may be if his RBC's are low. RBC's carry oxygen..so if his level is low that may be another reason. Unfortunatly that is a common side effect..he should mention that to his MD to make sure there is no other underlying cause. When this happened to my dad initally, I think because it was such a scary thing, he was less tolerant of it and it bothered him more. Now that he knows to expect it..he handles it better. I hope i was of some help to you..GOD bless and best wishes!