Oh how I feel for you right now. My two girls were aged 3 and 5 when I was diagnosed and it does make it just that little bit tougher. I was an emotional wreck - not so much for me but because I was thinking of them. We tried to be as honest as possible with our girls about what was happening to me. We said things such as there was a lump in my boob and the doctor needs to cut it out. Then I needed to have lots of medicine to make sure it doesn't come back. That the medicine is very, very strong and can sometimes make mummy feel tired and not very well but that it's making me better. We kept talking about what we would do when mummy was back to normal. I'm not sure how much a 1.5 year old would understand but I can imagine he will need lots of reassurance that you're ok. They pick up on so much of our emotions that I personally found it important to stay positive, that it's ok, I'm going to be ok - and that ended up having a huge positive impact on my own state of mind too. My older girl picked up on the seriousness of it all a couple of times and we had a little cry together but I also reassured her that I was going to be fine. They didn't visit me in hospital after my surgeries as I didn't want them to see me at my worst but we had some face time via the phone. My husband made a point of focusing on future activities and that worked for us, helped us all through. I hope this helps in some way. Sending you lots of hugs, mumma.
Sherril xo