mine started in the 2nd week of radiation,mostly occurs once but sometimes twice a day and less often any more than that (worst was having 5 before lunchtime) generally i can bring it up ok but 2 or 3 times a week have an eye watering time of it . i mentioned this to my oncology dr last visit and he sent me for precautionary chest xrays then at outpatient 3 month check with surgery dr he said the xrays came back all normal . i've gotten used to them and apart from the stubborn ones creating a gagging sensation they dont worry me to much.