I personally feel that a risk rise from a fraction of a percent to almost 10% isn't "quite low".PROTECTION FROM SPAYING
A female puppy spayed before her first heat cycle can expect never to develop a mammary tumor of any kind. The incidence of tumor development in this group is nearly zero.
If she is allowed to experience one heat cycle before spaying, the incidence rises to 7% (still quite low).
If she is allowed to experience more than one heat cycle, the risk is driven up to one in four.