I'm no medical expert, but did work in a dental set up for a good few years.

1) There are pre cancerous conditions, but these tend to be treated by topical methods (steroids, gels etc) rather than toxins like chemo

2) Oral cancers tend to be aggressive in nature, so a wait and watch approach is usually applied to pre cancerous conditions. The reason they're aggressive, is because cells in the oral cavity are fast-growing by their very nature, so the cancers tend to follow suit.

3) Not all pre cancerous conditions evolve into cancers

4) As mentioned above, chemo usually has an accumulative effect, so the main text book symptoms may only appear around the 3rd dose. They may never appear.

5) not everyone loses their hair or lose weight. My wife didn't. In fact, my wife put weight on due to the steroids.

6) Cancers can and do become resistant to chemos, so chemo is usually left until there is no other choice (not sure if that's the case in all cases). The more they can treat actual cancer using non chemo treatments, the better it is for the patient further down the road should things progress. So pre cancer chemo seems a bit off.

What makes you think he's lying? What reasons do you think he has to make this up? Did he ever have any sort of emotional quirks prior to this breakup? Has he ever used emotional blackmail on you before? For some bizarre reason, some people do go to these lengths and either threaten to kill themselves or conjure up some serious illness as to trap others emotionally. They place all the emotional fault/onus at the feet of their ex partner.

As it doesn't seem to be a serious, serious relationship, if you have doubts about his trustworthiness, now is the time to confront them and cut ties. You aren't responsible for his health or emotions, only he is, so if you think he's duping you, it's not the foundation upon which to build a long-term relationship on.

There's one way to find out for sure, ask to attend one of his appointments. Even if it means you are waiting outside the chemo building or go to one of his oncologist appointments. Most folk also get other drugs to go along with the chemo, anti sick meds, steroids etc. So ask to also see these other meds.If he doesn't agree to any of these or makes excuses, then your gut feeling is probably correct. If you turn up to his place, and he comes out with his chemo appointment or medical appointment is cancelled, it will also confirm he's at it. It's a well trodden method to say things have been cancelled at the last minute. He will also have these chemo and oncologist appointments in writing. My wife has a bag full of them. Ask to see his letters or emails regarding the hospital stuff.

Being 2022, tell him your doubts and get him to send a copy of a hospital letter via your mobile that will leave you in no doubt. Someone faking it, won't have those letters/email.