Hi, I am a 31 year survivor of stage 4+  NPC. I was 15 at the time.
Back then it was very rare. I was the 5th in UK to have it, and I know of 3 ladies in USA who had it around the same time and have survived.
Nowadays it is not so rare sadly, ,(around 240 per year in UK alone),  but there have been huge improvements in treatments, ( so he won't have many  long term side effects, as people like me who had very high dose of radiotherapy blasted at us have) and survival rates.  There is 80-90% survival rates nowadays and at least 50% of no recurrence within 5 years. There are lots of us in facebook support groups who can answer your questions and give reassurance, but feel free to message me too.
I know it is daft to tell a mum not to worry, but please take it one day at a time .

Thank you so much for taking the time to reply, and you were so young, you were very brave but have obviously lived long after the cancer but worse the treatment to make you better. Yes, my son has assured me the radiotherapy treatment has come on leaps and bounds, even in the last couple of years. He’s started chemo for 9 weeks first before he has chemoradiotherapy and is being very positive as are we all. He’s on his own but his sister is going for Xmas and I’ll be going soon too. I think it’s the shock as he’s a very healthy young man who looks after himself. I’ll have a look on Facebook and update on here how he’s getting on. Thanks again for your reassurance message. 

Thank you so much for taking the time to reply, and you were so young, you were very brave but have obviously lived long after the cancer but worse the treatment to make you better. Yes, my son has assured me the radiotherapy treatment has come on leaps and bounds, even in the last couple of years. He’s started chemo for 9 weeks first before he has chemoradiotherapy and is being very positive as are we all. He’s on his own but his sister is going for Xmas and I’ll be going soon too. I think it’s the shock as he’s a very healthy young man who looks after himself. I’ll have a look on Facebook and update on here how he’s getting on. Thanks again for your reassurance message.