I'm sorry you've joined the breast cancer club, OP. Best of luck with your treatment. It's tough, but it is doable.
As far as cooking goes, obviously your DH should do most of this. I would echo what others have suggested - e.g. bung stuff in a roasting tin - I do sausage (meat or veggie) tray bakes with onion, peppers, potato wedges, tin of tomatoes, garlic, chilli if you like. Takes 2 mins prep. Stir-fry - bag of stir-fry veg plus noodles. Pasta - with peas, pesto and parmesan. Pasta e cechi - I make a store cupboard version, fry garlic, add half a tube of Tom purée, lots of black pepper, then add pasta, tin of rinsed chickpeas, boiling water and a Knorr veggie stockpot (or bouillon)cook and have with parmesan. Baked potatoes or wedges with easy fillings or sides.
Roast veggies with couscous, crumble feta over the top, add rocket leaves and harissa.
Stock up the freezer with casseroles, chilli, lasagnas, some ready meals, oven chips, veggie burgers etc.
Takeaways.