The study aimed to determine whether adjuvant radiation therapy (RT) after breast-conserving surgery and tamoxifen provides additional benefit in women aged 70 years or older with early-stage breast cancer. Between July 1994 and February 1999, 636 women (age ≥ 70 years) with clinical stage I, estrogen receptor (ER)-positive breast carcinoma were randomly assigned to receive tamoxifen plus RT (TamRT) or tamoxifen alone (Tam). The primary endpoints were time to local or regional recurrence, frequency of mastectomy, breast cancer-specific survival, time to distant metastasis, and overall survival (OS). After a median follow-up of 12.6 years, the results showed that at 10 years, 98% of patients receiving TamRT compared to 90% of those receiving Tam were free from local and regional recurrences. However, there were no significant differences in time to mastectomy, time to distant metastasis, breast cancer-specific survival, or OS between the two groups. The 10-year OS was 67% for both groups. The study concluded that while the addition of RT provides a small improvement in locoregional recurrence, it does not translate into an advantage in OS, distant disease-free survival, or breast preservation. Therefore, tamoxifen remains a reasonable option for women aged 70 years or older with ER-positive early-stage breast cancer, depending on the value placed on local recurrence.The study aimed to determine whether adjuvant radiation therapy (RT) after breast-conserving surgery and tamoxifen provides additional benefit in women aged 70 years or older with early-stage breast cancer. Between July 1994 and February 1999, 636 women (age ≥ 70 years) with clinical stage I, estrogen receptor (ER)-positive breast carcinoma were randomly assigned to receive tamoxifen plus RT (TamRT) or tamoxifen alone (Tam). The primary endpoints were time to local or regional recurrence, frequency of mastectomy, breast cancer-specific survival, time to distant metastasis, and overall survival (OS). After a median follow-up of 12.6 years, the results showed that at 10 years, 98% of patients receiving TamRT compared to 90% of those receiving Tam were free from local and regional recurrences. However, there were no significant differences in time to mastectomy, time to distant metastasis, breast cancer-specific survival, or OS between the two groups. The 10-year OS was 67% for both groups. The study concluded that while the addition of RT provides a small improvement in locoregional recurrence, it does not translate into an advantage in OS, distant disease-free survival, or breast preservation. Therefore, tamoxifen remains a reasonable option for women aged 70 years or older with ER-positive early-stage breast cancer, depending on the value placed on local recurrence.