There is provided a system for tracking events associated with a treatment by personalised medicine, the system comprising a plurality of nodes hosting a blockchain. The plurality of nodes include a plurality of sequence manager nodes, each associated with a respective sequence manager contract on the blockchain, and a hub node associated with a hub contract on the blockchain. A first sequence manager contract of the sequence manager contracts is arranged to receive first event data indicating a first event associated with the treatment, and store the first event data on the blockchain in association with a first event sequence. The hub contract is arranged to store an association between the first event sequence and one or more further event sequences associated with the treatment, on the blockchain.