How soon after a lumpectomy should therapy start?

Within 6-8 weeks. Therapy can start any time one has healed from the surgery & has all the answers to know the next steps. If the next step is chemorx, most trials require starting rx within 6-8 weeks postop. If the next step is radiation rx, the same arbitrary deadline (although brachytherapy, which requires a catheter placement into the lumpectomy cavity, should be done within 3 weeks, before the cavity shrinks).