If you are told your cancer free and have taken chemo pills why would you need radiation

Past experience: "cancer-free" is a poor choice of words when you are still receiving therapy. We never know when the last cancer cell is gone. A better term would be "no evidence of cancer". With many cancers, we know from experience that without radiation the risk of cancer returning is higher, even when there is no evidence of cancer after chemo. Hence the recommendation for radiation.

Microscopic disease: Depending on the type of cancer, any combination of surgery, chemotherapy and radiation therapy may be needed to give the best chance of cure. Radiation therapy helps with local control of either macroscopic (for example, you see it by imaging or the surgeon couldn't safely remove it all) or microscopic disease (its there, but can't detect it).