To which I’d say yes both seem helpful to an organization that helps people in need.
But cash is much more universal and allows the cancer research organization to get exactly what they need rather then whatever needles people feel like donating. It's the same thing with food pantries. You can donate 10 cans of vegetable soup, but if the food bank doesn't need that at the time, you've just wasted your money on vegetable soup when you could have just donated cash.
I mean I guess a food bank would have food already as well... They are both one time use consumable supplies so, whether they have them or not, they are going to have to resupply at some point.