I am 6 yrs, as of 23 March 2017, out from HPV p16 H&N cancer from an unknown site. But they thought it was under-my tongue and gave 35 radiation treatments that focused on that area. They found the cancer cells in 2 of 41 removed lymph nodes BUT apparently no cancer cells got out of those 2 nodes. Hence, I have no experience with the movement of cancer cells to other parts of my body as of my last checkup. I go in every 6 months. My response is regarding your question on whether scar tissue can have an affect on your swallowing? The answer is YES! I just had a swallow test and it was determined that the scar tissue caused by the intense radiation treatment affected the valve that opens and closes when I eat anything. It prevents food from going down the wrong hole to the lungs. Thus, eating is task but must done or use a feeding tube. I did that for 4 months but won't do again, unless needed. Sorry to say, you will need to learn how to swallow again with this permanent issue. Once you do that, life gets easier. God Bless!