Cancer is evil. Even dogs with the same type will present differently. Sirocco's os first appeared as a limp. A month later, a huge lump suddenly appeared on his shoulder and a month after that, he was gone. His xrays always looked good. Nikki's os didn't present until she stepped off the deck and her leg shattered. Never a lump, never a limp and never a whine.
I was never negligent with their health care. My motto has always been "when in doubt, check it out". But, cancer is evil and evades all our good intentions. If we don't xray we could be missing something but if we do we could be exposing our dogs to too much radiation. All we can do is try our best and be there for each other.