Table 1.

Summary of trials on radiotherapy for oligometastases in breast cancer

First author, year	N	FU (months)	Study design	Number of metastases	Subtype of OMD	Sites	Previous systemic therapy	Fractions/doses	Toxicity	–	OS	PFS	LC
Tsai et al., 2021 [15]	44	–	Prospective, randomized	1: 25 % > 2: 75 %	Oligoprogression	–	100 %	SBRT (no further information available)	≥ Grade 2: 26.7 %	–	–	4.5 months (SBRT) vs. 4.3 months	–
David et al., 2020 [16]	15 (19 met)	24	Prospective, single arm	1: 73 % 2: 27 %	Synchronous OMD 13 % Metachronous OMD 87 %	Bone 100 %	87 % (endocrine)	1 fx/20 Gy	Grade 1: 67 % Grade 2: 27 % No grade ≥ 3	2‑year	100 %	65 %	100 %
Milano et al., 2019 [10]	48 (102 met)	52.8	Prospective, single arm	1: 39.6 % 2: 31.3 % 3: 14.6 % 4: 6.2 % 5: 8.3 %	Synchronous OMD (17 %) Metachronous OMD (83 %)	Bone 25 % Lung, lymph nodes, liver, adrenal 75 %	91 % (56.2 % endocrine)	5–10 fx (10 fx in 56.3 %; 1 patient < 5 fx)/ 3–17 Gy per fraction (in all but 2 patients)	n/a	5‑year 10-year	5‑year: 31 % (excluding bone) vs. 83 % bone only 10-year: 31 % (excluding bone) vs. 83 % bone only	n/a	10-year: 73 % (excluding bone) vs. 100 % bone only
Trovo et al., 2018 [19]	54 (92 met)	30	Prospective, single arm	1: 50 % 2: 35.1 % 3: 11.1 % 4: 1.9 % 5: 1.9 %	Synchronous OMD 74 % Induced OMD 26 %	Bone 65.2 % Lymph nodes 25 % Lung/liver 9.8 %	89 % (17 % endocrine)	3 fx/30–45 Gy (n = 44) or 25 fx/60 Gy (n = 10)	No grade ≥ 3	1‑year 2‑year	97 % 95 %	75 % 53 %	97 % 95 %
Scorsetti et al., 2016 [17]	33 (47 met)	24	Observational, single arm	1: 63.6 % 2: 30.3 % 3: 6.1 %	n/a	Liver, lung 100 %	90.9 %	3 fx/56.25–75 Gy (for liver met); 4 fx/48 Gy (n = 13) or 3 fx/60 Gy (lung met)	Grade 3: 18 % No grade ≥ 3	Median 1‑year 2‑year	48 months 93 % 66 %	11 months 48 % 27 %	n/a 98 % 90 %
Lemoine P et al., 2021 [18]	44	40.8	Retrospective, single arm	1–5	n/a	Bone 44.4 % Liver 40.7 % Lung 11.1 %	52.8 % (29.5 % endocrine)	3–10 fx (median 3)/15–54 Gy (median 40)	Grade 1: 25 %, grade 2: 7 %, no grade ≥ 3	Median 1‑year 2‑year 3‑year	n/a 93 % 87 % 81 %	31.2 months 81 % 58 % 45 %	n/a 100 % 100 %
Tan et al., 2021 [21]	120 (193 met)	15.3	Retrospective, single arm	1–5	OMD 55 % Oligoprogression 30 % OMD with intention of local control of dominant tumor 15 %	Bone 59.20 % Liver 20 % Lung 17.5 %	91.7 % (84 % endocrine)	4–5 fx/48–52 Gy 3–5 fx/30–60 Gy 5 fx/30–40 Gy 2 fx/24 Gy 4–5 fx/30–35 Gy (regimen depending on organ affected)	Grade 3: 4.2 % (3 radiation pneumonitis, 2 vertebral fractures)	Median 1‑year 2‑year	53.16 months 83.5 % 70 %	11 months 45 % 32 %	n/a 89 % 86.6 %
Wijtunga et al., 2021 [31]	79 (103 met)	50	Retrospective, single arm	1: 80 % > 1: 20 %	Metachronous OMD (44 %) Oligoprogression 47 % Oligopersistence 9 %	Bone 93 % Lymph nodes 4 % Lung 2 % Skin 1 %	n/a	1 fx/18–24 Gy 3 fx/24–30 Gy 4 fx /40–48 Gy 5 fx/25–35 Gy 8 fx/40 Gy	No grading given Toxicity/symptoms: At baseline: 66 % Acute (up to 2 weeks post RT): 49 % Subacute: 73 % Late (after 6 months): 29 %	Median 2‑year 4‑year	86 months 91 % n/a	33 months 57 % n/a	n/a n/a 70 %
Weykamp et al., 2020 [20]	46 (58 met)	21	Retrospective, single arm	1: 80.4 % 2: 17.4 % 3: 1.7 % (> 3 met in total, but 1 progressive oligoprogression: 30 %)	Metachronous OMD 70 % Oligoprogression 30 %	Bone only 56.3 % Liver 25 % Brain 6.3 % More than 1 site 12.6 %	71.7 % (58.7 % endocrine)	1–10 fx/5–30 Gy per fraction	Grade 1: 16 % Grade 2: 2 % No grade ≥ 3	1‑year 2‑year	85.4 % 62.1 %	54.3 % 17 %	92.2 % 89 %
Onal et al. 2018 [32]	22 (26 met)	–	Retrospective, single arm	1: 86.4 % 2: 9.1 % 3: 4.5 %	Metachronous OMD 14 % Oligoprogression 86 %	Liver 100 % (31.8 % liver-only)	100 % chemotherapy (4 neoadjuvant, 18 postop)	3 fx/54 Gy	Grade 3: 9.1 % (1 rib fracture, 1 duodenal ulcer) No grade 4	Median 1‑year 2‑year	n/a 85 % 57 %	7.4 moths 38 % 8 %	n/a 100 % 88 %

OMD oligometastatic disease, OS overall survival, PFS progression-free survival, LC local control, RT radiotherapy, fx fractions, met metastases