Is whole body PET scan required to check the spread of tongue cancer?

Hi doctor,

My father is 65 years old and in excellent health. He is a diabetic and also has BP. But, his sugar levels and BP are very much in control. He is taking oral medication for both diabetes and BP. He is taking Telvas 20 mg for BP, Gluconorm for diabetes and taking thyroid medication for hypothyroidism (25 mg). He has been diagnosed with initial stage squamous cell carcinoma of the tongue. We first noticed symptoms around two months back, because of a blister on my father's tongue which did not heal despite of vitamin B complex medication and antibiotics. The medical oncologist we were referred to examined my father and said that it is in the very initial stage and it is highly unlikely to spread. Even if it has, at the maximum it would be in the lymph nodes near the tongue. We opted for a PET CT scan to be sure and the doctor prescribed only a head and neck scan. The scan results mentioned an SUV level of 5.3, suggesting malignancy on the tongue and an SUV level of 3.1 in level I, II and III lymph nodes, which the radiologist mentioned were non-specific. I would like to add that my father had a minor cold when the scan was done.

Based on the scan results our doctor has suggested surgery to remove the cancerous portion of the tongue and the lymph nodes, though it is not clear whether they are affected or not. He also mentioned that after removal again the lymph nodes would be tested for malignancy. He underwent PET CT scan, serum creatinine, CBC and blood tests. My question is should we have to go for a full body scan instead of just the head and neck? With respect to the lymph nodes, is the SUV number suggestive of cancer? Or could it be higher because of the cold my father had? Thank you very much for your response in advance.