It's important to distinguish weight loss between explained and unexplained, though; explained weight loss would mean that it stems from a known and identified cause. This would usually be a lower intake of calories or increased activity - or both. Those are the usual causes of weight loss in dementia - espescially if patients forget to eat, or refuse to. Or they may suddenly start pacing/wandering a lot.
Unexplained weight loss means that it can't be obviously accounted for. It will ring alarm bells in any doctor as it can indicate some underlying problem. Cancer is of course the most well known of these although there are many others.
Unexplained weight loss in conjunction with other symptoms would certainly raise red flags because together they may indicate a serious problem. People very rarely "just lose weight".
It would be most unusual for any doctor who had the least suspiscion of cancer to not make a referral.
As said, night sweats have many benign causes, but they also have serious ones.
Of course, it should be kept in mind at all times that cancer is in fact rare and very often even suspiscious symptoms turn out to not be cancer.
