Article 2(27) of the CTR defines early termination as
"the premature end of a clinical trial due to any reason before the conditions specified in the protocol are complied with".
However, when the protocol specifies circumstances that would determine an early termination of the clinical trial, the sponsor needs to report also an early termination of the clinical trial in case such prespecified circumstances occur.
Early termination of a clinical trial for reasons not affecting the benefit-risk balance should be reported in CTIS within 15 days. Early termination for reasons of subject safety should be reported in CTIS without undue delay but not later than in 15 days. In both cases the report shall include the reasons for such action and specify follow-up measures for the subjects.
See also Question 10.10 and 10.11 of the Q&A CTR.