That is a symptom that warrants you getting in touch with your team without much delay. Could be anything from a trapped nerve in your back, to the chemo.

I'm assuming it's your leg only? Not in your saddle area (like your buttocks, pelvis etc)? Your bowels and bladder habits are ok?

There's a condition called cauda equina syndrome that happens due to severely compressed nerves in your back and you need to rule that out as a matter of urgency. Doesn't sound like it is, but it can present like this.

Hello and thank you for your post,

Yes, as ProfBaw has said please do let your chemotherapy team, on the number they have given you, know about this. I am afraid I can't tell you what is the matter so to be on the safe side get checked out. Do also let the team know about any other symptoms you may have.

Please get back to us if you need any more information or support. 

Your sincerely,

Caroline