Table 7. Oligometastatic colorectal cancer.

1st Author, Year [Ref]	Strength of evidence- based on study design / endpoint	Prospective (P) / Retrospective (R)	Sample size	Definition- Oligo metastases	Therapy	Endpoint	Conclusion
Engels, 2012 [104]	2 /A	P	24	≤ 5 mets	Resected primary tumor, and inoperable mets treated with helical tomotherapy	1yr OS- 78%	Helical tomotherapy is an attractive for consolidation of inoperable OM disease after effective chemo
Dellas, 2012 [110]	2/ D	P	9	1–3 mets or local recurrence plus max. 2 mets	CT + 3D-CRT to all met lesions	3/9 pats survived 3.5–4.4 yrs; DLT not documented	3D-CRT to mets feasible in addition to standard CT
Van den Begin, 2014 [113]	3ii/A	R	47	Resected primary + ≤5 mets, liver, lung, LNs	SBRT	1yr OS- 53%	Nature + location of local recurrences demonstrated need for breathing management and dose >75Gy.
Filippi, 2014 [114]	3ii/A	R	40	Resected primary + 1–5 lung mets, max diameter <5cm	3D conformational RT or image guided volumetric modulated arc therapy	5yr OS- 39%	Suggests stereotactic ablative RT is safe + efficacious in CRC with lung oligometastases
Kang, 2010 [117]	3iii /A	R	59	1–4 met lesions confined to 1 organ, largest <7cm, progressive after CT	Met lesions progressed after chemo, then treated SBRT	5yr OS- 29%	Patients generally fare well after SBRT
Salah, 2012 [112]	3iii /A	R	927	Underwent lung metastasectomy	Lung metastasectomy	5yr OS- 54.3%. Prognostic risk groups good-, intermediate-, and high-, had 5yr OS- 68%, 46%, 26%	More studies need to investigate if surgery offers advantage over CT in the poor-risk group
Bae, 2012 [116]	3iii/A	R	41	Met lesions confined to 1 organ	3 fractions SBRT	5yr OS- 38%	SBRT results comparable with Surgery
Salah, 2013 [115]	3iii /A	R	148	Repeat resection of pulmonary mets	Repeat resection of lung met	5yr OS- 52% for 1 lung met resection, 58% 2 lung met resection. >2 lung mets + ≥3 cm risk factors for decreased survival	In selected patients, repeated pulmonary resection offers good survival outcome
Comito, 2014 [111]	3iii/A	P	82	1–3 inoperable mets in 1 organ (Liver or lung)	SBRT	3yr OS- 43%	SBRT safe + feasible treatment for mets not amenable to resection

Abbreviations: Met(s) = metastasis(es); OS = overall survival; CT = chemotherapy; CRT = chemoradiation therapy; DLT = dose-limiting toxicity; SBRT = stereotactic body radiation therapy; LNs = lymph nodes; RT = radiation therapy; CRC = colorectal cancer