Table 3. Definitions of Oligometastasis.

Terms	Definition	Reference
Oligometastasis	“…metastases (from tumors early in the chain of progression) limited in number and location because the facility for metastatic growth has not been fully developed and the site for growth is restricted…”	[46]
Oligometastatic disease	Solitary or few detectable metastatic lesions that are usually confined to a single organ	[50]
Oligometastases	Due to limited metastatic competence and does not occur following otherwise successful systemic treatment. New metastases in this situation, albeit even limited, is likely to have more extensive malignant capabilities that were somehow spared from eradication by therapeutic means, or from the development of resistant clones	[15]
Induced oligometastases	Occurs when widespread micrometastatic disease is mostly eradicated by systemic chemotherapy but drug resistant clones are left behind, or tumor foci is located in a site not accessed by chemotherapy	[4]
Oligorecurrence	Limited metastases in the presence of a controlled primary lesion	[195]
Sync-oligometastases	≤5 metastatic or recurrent lesions in the presence of active primary lesions	[196]
Synchronous oligometastasis	Oligometastatic disease is detected at the time of diagnosis of the primary tumor, therefore there is an active primary tumor	[196]
Metachronous oligometastasis	Development of oligometastatic disease after treatment of the primary tumor; interval for classification of metachronous versus synchronous is not standardized; between Controlled primary lesion except for concomitant primary and distant recurrence	[196]
Oligoprogression	Progression of a limited number of metastatic deposits, while remaining metastases are controlled with systemic therapy	[197]
Oligometastasis (specific to prostate cancer)	Rising PSA following primary therapy, with oligometastasis on imaging, in whom local treatment (surgical metastasectomy (usually LN dissection), or SBRT for bony mets or LN recurrence) is required to defer initiation of ADT	[54]
Oligometastasis (specific to prostate cancer)	Castrate resistant prostate cancer with a rising PSA and oligometastasis on imaging, in whom local treatment (surgical metastasectomy (usually LN dissection), or SBRT for bony mets or LN recurrence) may allow deferral of ADT	[54]

Abbreviations: LN = lymph node; SBRT = stereotactic body radiation therapy; mets = metastases; ADT = androgen deprivation therapy; PSA = prostate-specific antigen