Cable television giant Comcast Corp. suffered a significant setback last week when a federal judge refused to dismiss a class action antitrust suit that accuses Comcast of setting out to establish monopolies in the Philadelphia and Chicago markets and then increasing prices once it had eliminated all the competition.

The suit could reverberate throughout the cable industry because it alleges that many of the big cable companies cooperated in carving up much of the nation into separate markets where each would be exclusive providers.