Hello, My Dad Had Kidney Cancer And We Discovered It

Hello, My dad had kidney cancer and we discovered it 4 months ago. Cancer was in his kidney (primary) and some doctors assumed it had moved to the liver (secondary) but scans showed the liver clear and my dad performed an operation and removed his left kidney. My dad, however, was suggested to do thyroid gland scans which he did. We got the results today and it was 1000 while the doctors said it should be around 4. Some doctors suggested it might be becaue of the anti cancer medication he takes but they're not sure. Can you please help me know if it's because of the medicine and can it do any harm?