Welcome dhav. Sorry for your girlfriend's diagnosis, and surgery. The good thing, T1 has a very high cure rate, so plan on. It's not that PET scans can't detect T1 tumors, but ones that are less than 1cm in size. T1 are less than 2cm. You are correct there are no tests to detect sccc cancer, but there are gene, protein expressions, and other indicators for possible cancer. Oral cancer is more easily detected being more in view than the oropharynx, so any changes, suspicions that lasts more than 2 weeks, should be seen by a doctor, and regular follow-ups should be made with your doctors. Oral cancer is mostly caused by smoking, but see in the signature your GF is a non smoker. The other causes are alcohol, viruses, and other suspected causes, exposure to carcinogens, and sometimes some have no risk factors. HPV is in the oropharynx 90 percent of the tim, but can be elsewhere in the oral area, and a few others. I assume the doctors checked the oropharynx, esphogus during surgery with an esphoscopy, triple scope?

As mentioned, the links on OCF are bery helpful, and can explain everything better, but hope I answered some of your questions.