I agree with David - take the 5 weeks. The typical recovery time formula for radiation is 1 month for every week of treatment, so that would be 7 months. Some have gone back early and did ok. Others mentioned that they went back too early.

The other item to be concerned with, especially because you had chemo, is your immune system. A common cold can give you pneumonia if you are not very careful, so exposure to sick people should be avoided. Make sure that you are practically obsessive compulsive about disinfecting surfaces and items that others touch and wash your hands frequently. Carry waterless hand cleaner with you as well. If you can telecommute, even better