If lung cancer is found early (still a small nodule,) can it be cured, or can it only be treated. Some sites say that lung cancer can not be cured.

It can be cured. New guidelines have urged yearly low level ct scans to be done in smokers and smokers that have quit within the last several years. This will hopefully pick up early cancers that can be surgically cured.
Don't believe. .Everything you read in websites. That's my first advise. Like with any cancer, the earlier you find a lung cancer, the better the chances of a potential cure. Now don't get me wrong, lung cancer stage by stage has a worse prognosis compared to others, let's say breast cancer, and this is complicated by the fact it is seldom found early, so it's best to prevent it. That said, some are cured.