Date of most definitive surgical resection of the primary site performed as part of the first course of treatment. See Data Descriptor Table for date format. Use RX DATE MST DEFN SRG FLAG [3171] if there is no appropriate or known date for this item.
 
Formerly RX Date--Most Defin Surg.

This item is used to measure lag time between diagnosis and the most definitive surgery of the primary site or survival following the procedure. It also is used in conjunction with RX Date Surg Disch [3180] to calculate the duration of hospitalization following the most definitive primary site surgical procedure to evaluate treatment efficacy.