How to apply a prefixed boundary in Active Contour Method?

I have two codes fo image segmentation. One is Watershed Method, and the other is Active Contour Method. In the Active Contour Method code, I have to select a boundary using the roiplay function.

%% create a mask for the breast
B=roipoly(img);

However, in the Watershed Method code, a boundary is already created by the method, and the boundary is implemented in this way:

[B,L]=bwboundaries(tumor,'noholes');
for i=1:length(B)
 [rows, columns, numberOfColorChannels] = size(img);
mask = poly2mask(B{i}(:,2),B{i}(:,1), rows, columns);
end

Where the proparties of tumor is alreay defined.

And the output figure is this:

I want to apply the same boundary to Active Contour Method, without using roiplay. My goal is to merge two codes, where I get the boundary from watershed method, and the boundary is applied into active contour. How can I do that?