Is it possible to update my system Cache

When my site starts up I put my "entities" [users, biz units etc] into  cache.

System.Web.HttpContext.Current.Cache[InnEnum.CacheName.EntityCache.ToString()] = e;

There are two fields in each row that can be modified by the user from the site.  I currently hit the DB to do the update but, I want to also update the cache without reloading the entire thing.  Is there a way to update the item[row] in the cache that pertains to the user record?

What is the best approach?

running SQL server 2008/10, .NET 4.0

thanks tons.