My mum is having a PET scan at the end of July. Her last scan was a CT scan in mid May which showed that the tumour had shrunk by half. The doctor said that it was "excellent" news. My mum started immunotherapy (durvalumab) in June. I'm worried that there won't be any progress or the cancer will have progressed or God forbid spread. My mum finished chemo (cisplatin) and radiotherapy in April. My mum's doctor said to her not to worry about the scan. I think I'm more worried than my mum. I know that they have to do scans as it's the only way to check on things and I know everyone goes through it. I've also heard about pseudo regression from chemotherapy. How common is this? By the way my mum was diagnosed in Feb with 3B non-small cell, squamous cell lung cancer. Also do doctors change the staging for example if the cancer shrinks i.e. can the doctor say it's gone from 3B to say 2B or is it always referred to by the original stage which it was first diagnosed regardless of improvement?