I agree with Dr Pandey to some extent. It is possible to cultivate some type of cancer cells without serum, as per my experience. Try to culture them for not more than 48 hrs otherwise fibroblast will be stressed and can loose their normal functionality.
You can cultivate the different cell lines under very low serum (5 or 10%) environment, however, you have to check the cell line stability and cellular morphology as per the ATCC Cell Line Authentication Test Recommendations. If you find fibroblast cells in good shape under the desired experimental conditions, you are good to go.
Please find the below link for your ready reference regarding guidelines.