s . ▁Several ▁studies ▁have ▁reported ▁that ▁the ▁presence ▁of ▁these ▁clusters ▁is ▁associated ▁with ▁increased ▁met ast atic ▁risk ▁and ▁poor ▁pro gn osis . ▁For ▁example , ▁one ▁study ▁involving ▁pro state ▁cancer ▁showed ▁an ▁eight - fold ▁longer ▁mean ▁surv ival ▁rate ▁for ▁patients ▁with ▁only ▁single ▁C TC s ▁versus ▁those ▁with ▁C TC ▁clusters , ▁while ▁other ▁studies ▁have ▁shown ▁similar ▁correl ations ▁for ▁colon ▁cancer . ▁In ▁addition , ▁enumer ating ▁C TC ▁clusters ▁can ▁provide ▁useful ▁pro gn ost ic ▁information ▁for ▁patients ▁with ▁already ▁elev ated ▁C TC ▁levels . ▁ ▁However , ▁one ▁study ▁has ▁reported ▁that ▁contrary ▁to ▁existing ▁cons ensus , ▁at ▁least ▁a ▁discrete ▁population ▁of ▁these ▁clusters ▁are ▁non - m align ant , ▁and ▁derive ▁instead ▁from ▁the ▁tum or ▁end oth el ium . ▁These ▁circul ating ▁tum or - end oth el ial ▁clusters ▁also ▁show ▁ep ith el ial - mes en ch ym al ▁markers ▁but ▁do ▁not ▁mirror ▁the ▁gen et ics ▁of ▁the ▁primary ▁tum or . ▁ ▁Pre viously ▁it ▁was ▁assumed ▁that ▁C TC ▁clusters ▁could ▁not ▁pass ▁through ▁narrow ▁vessels , ▁such ▁as ▁cap ill aries , ▁due ▁to ▁their ▁overall ▁size . ▁However , ▁it ▁has ▁been ▁shown ▁that ▁C TC ▁clusters ▁can ▁" un wind " ▁through ▁" select ive ▁cle av age ▁of ▁inter cell ular ▁ad hes ions " ▁to ▁traverse ▁these ▁con str ict ions ▁single - file , ▁then ▁reverse ▁the ▁process ▁once ▁clear