1 Tamoxifen (brand name: Nolvadex) can be used for early-stage cancers that are hormone-receptor-positive, instead of or following radiation treatment after lumpectomy. 2  Tamoxifen pretends to be estrogen and attaches to the receptors on the breast cancer cells, taking the place of real estrogen. Radiation treatment is usually given as daily treatments 5 days per week over 5 to 7 weeks. 2  Treating the whole breast with radiation after lumpectomy remains the standard of care. 3  In cases of DCIS, radiation therapy can reduce the risk of the cancer coming back by about 60%.