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Abstract
Aim: Patients with locoregionally uncontrolled breast tumors are frequently referred for breast palliative radiotherapy (PRT) to mitigate symptoms. We analyzed the outcomes following breast PRT to optimize PRT according to risk groups.

Methods: We reviewed 133 patients who underwent breast PRT. A median total dose of 45 Gy was prescribed with an equivalent dose in 2 Gy fractions (EQD2, α/β = 3.5) of 53 Gy. The Cox proportional hazards model was used to analyze the prognostic factors of local control (LC).

Results: Most (90.2%) had polymetastatic disease (> 5 lesions), and 48.9% had bone metastasis. With a median follow-up of 17.2 months, the 2-year LC and overall survival (OS) rates were 49.4%, and 48.3%, respectively. Multivariable analyses demonstrated progressive or mixed responses outside the breast and > 2 lines of previous therapy as adverse features for clinical outcomes. Group 1 (0 risk factors) showed favorable 2-year LC and OS of 63.9%, and 72.8%, respectively, whereas group 3 (2 risk factors) showed the worst outcomes of 0%, and 6.8%, respectively. Breast PRT with EQD2 ≥ 63 Gy showed a significant benefit in LC for group 1 and marginal benefit (p = 0.055) for group 2, but no improvement for group 3 (p = 0.300).

Conclusion: Breast PRT showed favorable LC outcomes in patients with stable disease outside the breast and treated with ≤ 2 lines of systemic treatment. Our findings warrant future clinical trials investigating the role of higher than palliative dose and early intervention of PRT in stage IV patients.

Affiliations

Nalee Kim 1, Haeyoung Kim 2, Won Park 1, Won Kyung Cho 1, Tae Gyu Kim 3, Young-Hyuck Im 4, Jin Seok Ahn 4, Yeon Hee Park 4, Ji-Yeon Kim 4
1Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 06351, Republic of Korea.
2Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 06351, Republic of Korea. haeyoung0131.kim@samsung.com.
3Department of Radiation Oncology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea.
4Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.