Do we understand the early dynamics of cancer? Do the hallmarks need to appear more or less at the same time by chance, or can the cancer cells acquire them sequentially, which would then induce a local microevolution process?

>>> generally, an organism with a malignant tumor is less likely to reproduce.

Huh?

What is meant by this? Like if you have cancer, you are less likely to want to reproduce? Or, less likely to reproduce due to the illness?