Scientists say they have made a discovery that may help explain the racial gap in cancer survival, providing clues to why white patients often outlive blacks even when they have what appear to be the same cancers. The insights come from research at the University of Maryland into throat cancer and squamous-cell cancers of the head and neck, which have been increasing sharply in recent years, apparently because of the human papillomavirus — the same sexually transmitted virus that causes cervical cancer and is the target of a vaccine for girls. The virus can also be spread through oral sex,...