A radioconjugate containing the acetate salt of eribulin, labeled with the beta particle-emitting radioisotope carbon C 14 , with radioisotopic and potential antineoplastic activities. Upon administration, eribulin binds to the vinca domain of tubulin and inhibits the polymerization of tubulin and the assembly of microtubules, resulting in inhibition of mitotic spindle assembly, induction of cell cycle arrest at G2/M phase, and, potentially, tumor regression. The radioisotope moiety of this agent acts as a radioactive tracer.