@Karl *****
, If you apply for a new extension before the normal window of application for a new 1-year extension, yes, you do.
But when you are in the window of the standard period of your next 1-year extension, from 30 days (or 45 days depending on the IO) before and until the due date of the current extension, you can just apply for a new 1-year extension based on marriage. <- this is the 'changing reason for an extension'. You don't have to apply for cancellation officially for this.