A bit worried about weight loss

I just finished 35 radiation treatments 10 days ago or so. I lost my ability to swallow about 4 weeks ago and have been feeding on Boost 530 kcal drinks through a feeding tube. I’ve mostly been consuming 5 Boosts a day. Even at 2650 kcal per day and not having radiation for 10 days I’m still losing weight. I am 62M 6’1” regularly 185 lbs. I dropped probably 8 - 10 lbs before treatment. I just weighed myself at 153.5 lbs! Why!?