How to update options after sync in Javascript?

Hi,

we have a multiselect with some deprecated values. The deprecated values should be removed if not in saved values. This is what I tried in the module record..js:

    _filterLocations: function()
    {
          var location_c = this.model.get('location_c'), skipList = ['dus6.2'], i = 0;

          if (typeof location_c != 'undefined') {
              var list = app.lang.getAppListStrings('data_center_list');
             Object.keys(list).forEach(function(key) {
                  for (i in skipList) {
                       if (key == skipList[i] && ! location_c.includes(key)) {
                            delete list[key]
                       }
                  }
             })
             this.model.fields['location_c'].options = list    
          }
    }

The function is called by sync: this.model.once('sync', this._filterLocations, this)

With console.log(list) is 'dus6.2' removed, but not in the page view.

How can I update / re-render the select values?

We are using SugarCRM 7.9

Regards

Harald