The May 2022 CTR Coding Break titled First Course vs Subsequent Treatment discusses first course and second course treatment standard setter definitions, the differences between the two courses as well as a few case examples. First course treatment is the initial plan of treatment, includes any modality of treatment and may last a year or more. First course treatment has an ending point with different scenarios of disease progression, recurrence or treatment failure. Second course treatment is described as any treatment given after the 1st course of treatment is completed, stopped or changed. Once the patient starts 2nd course treatment/subsequent treatment, the patient can no longer be administered any 1st course treatment. Prostate cancer is unique and has active surveillance as a first course of treatment option depending on staging. Any prostate treatment given after active surveillance is subsequent treatment. Per SEER Program Coding and Staging Manual, treatment given as first course for an unknown primary remains first course even if the correct primary is later identified.