In cancer follow-up, in addition to the evaluation of survival probabilities, there is a fundamental need of assessing recurrence dynamics for optimal disease management. In breast cancer, although the time-dependent effect of the oestrogen receptor (ER) status of the tumour has already been described, so far no factor has proven to disentangle the multi-peak behaviour observed for metastatic recurrences. We proposed frailty models in the tumor dormancy framework, in order to account for possible unobservable dependence mechanisms in cancer studies where a non-negligible proportion of cancer patients relapses years or decades after surgical removal of the primary tumor.