Backbone fetch onto node.js / MongoDB not filtering results

I have backbone function that get data via a node.js server with MongoDB. I am doing a fetch and getting all the data back fine, but it does note seem to filter it based on the data request in the fetch statement:

    getItems: function (listId)
    {
        this.list = new List({_id: listId});
        this.list.fetch();  
        console.log(listId);
        console.log(this.list);
        this.itemCollection = new ItemCollection();
        this.itemView = new ItemView({model: this.itemCollection},this.list);
        this.itemCollection.fetch({data: { list: listId }, processData:true});  // << THIS IS PROBLEM LINE          
        console.log(this.itemCollection);

        return this.itemView;
    },   

My item collection is:

define(['jquery', 'underscore', 'backbone', 'model/ItemModel'
], function($, _, Backbone, Item){

var ItemCollection = Backbone.Collection.extend({
    model: Item,
    url: "/api/items"
});

return ItemCollection;

});

My Item Model is: define([ 'jquery', 'underscore', 'backbone' ], function($, _, Backbone){

var Item = Backbone.Model.extend({
    urlRoot: "/api/items",
    defaults: {
            name: "",
            done: false
    },
    idAttribute: "_id"          
});

return Item;

});

My Node API is:

app.get('/api/items', function (req, res) {
return ItemModel.find(function (err, item) {
    if (!err){
        return res.send(item);
    } else {
        return console.log(err);
    }
});
});

Hope that's enough info to give you and idea of what I'm trying to do. At the moment I am getting every item back from the database, not just the items with the correct listId.

Thanks for any help.