The ethics committee of the Japan Society of Clinical Oncology has compiled a proposal saying it is "too early" to approve of the freezing of female cancer patients' ova, society officials said Monday.

The committee expressed wariness toward the idea of freezing the ova so that the women -- whose ova are at risk of being damaged due to their cancer treatment -- may have children in the future, saying the technology and safety of such a step have yet to be established.

The society is expected to put its official recommendation forward by the end of next year.