Just saw a study which says lab dogs get cancers more than other breeds. The report supported that the genetics of labs is what causes them to get more cancers. That takes a really smart person to come up with that. NOT!
 I have thought for years that all dogs are more prone to getting cancers because of the flea/tick chemicals we put on them. Nothing to do with their genetics. SO, I will say I have been treating four dogs without chemicals, to keep the fleas and ticks off them. It was dumb luck I discovered that yogurt keeps fleas/ticks off dogs. I really was treating my dogs for dry skins and scratching. The yogurt really took care of the skin issues. But then I realized my dogs were not getting fleas and ticks. My neighbors dogs have fleas/ticks. So, I would suggest you take off all chemicals from the dogs' neck. Your dog is relying on you to take care of it.