Good points HouseBeauty, you're very right and I might have misunderstood the original post.
I completely agree that cancer isn't something to be scared of. I'm not qualified to do lymph drainage massage on a damaged lymph system, but I will massage anyone at any stage of their cancer journey. This is because I trained though, I don't think anyone should "have a go" on a client on the basis of gut instinct, intuition and best intentions. Training empowers you with the knowledge you need to realise how safe it is to massage people living with cancer.
In the UK, cancer isn't covered by standard training and you do need to train in order to be insured. If you start doing treatments which your insurers would refuse to cover, you might actually void your entire policy, not just the clients you take outside your insurance cover. (Insurance is slightly off topic, so I won't go into this).
I wasn't aware that Hospices would train you from scratch. I trained first. There are lots of excellent cancer training courses and even brands that specialise in cancer treatments. Most families are affected by cancer so if you are in business for long enough, all of your clients will need support from you at some point. It makes commercial sense to train in cancer and it's emotionally very rewarding.