Database Table Sizes Extremely Large (opigno_answer_revision__field_xapidata and opigno_answer__field_xapidata)

Our database tables are getting extremely large. opigno_answer_revision__field_xapidata and opigno_answer__field_xapidata are both over 15 GB in size and are making backing up and working with the database extremely difficult. Are these tables required? They seem excessively large. Can we safely truncate them and still have all student answers available to us? If we can't just truncate, what is the process for reducing these table sizes?