Could Stop Smoking Shot be related to Salivary Gland Cancer?

My husband was diagnosed with a salivary gland cancer, went through treatment and he is doing fine now. About 8 months before diagnosis he had the stop smoking shot which is an injection right around the saliva gland followed up with a patch that has to be worn for about 3 days behind the ear. It has been about 2 years since- but it has always stuck in my mind that this could have contributed if not caused the cancer. The doctors all have said that his particular cancer was not related to smoking. They don't really have much to say about the shot. How can I find out if there are others out there that this has happened to?

By the way the shot worked for a short time about 3 months. What made him quit for good was the cancer. Cold Turkey

Also, for any of you out there with swollen saliva glands get it checked out don't wait. They thought he had a blocked duct. We found out during treatment that this happens to many people. The only way for them to find out if a persistant swollen gland is cancer is for them to do an asperation.