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In cognitive radio (CR) networks, upon the request of a primary user (PU) to utilize the licensed spectrum, all the secondary users (SUs) using the same licensed spectrum must terminate the spectrum usage immediately and switch their data transmissions to unoccupied spectra to avoid interference with the PU. The spectrum switching may lead to severe throughput degradation in SU networks. To mitigate the impact of spectrum usage termination and switching, Minimum Interference Robust Topology Construction (MIRTC) is a critical problem. In this paper, we formulate the problem as an integer programming problem and propose a genetic-algorithm-based channel assignment (GACA) scheme to construct a robust CR topology while minimizing interference. Our proposed formulation maintains the connectivity of each source-destination pair under the interruption of any single channel. A Bisearch algorithm is further proposed to approach the optimal solution of the problem. Simulation results demonstrate that the proposed scheme can reduce network interference and enhance network throughput efficiently.