Yes, there were two endings. The theatrical ending featured surviving heroine Cynthia kneeling to pet a dog, which then shoots a leech out of its mouth.
The original ending, though, featured Det. Cameron walking around, burnt to a crisp; he collapses and a bunch of leeches burst out of him, scamper off to a cemetery and then a space ship is shown hovering over the cemetery in search of the leeches. I'm not sure why this ending was dumped in favor of the dog ending for the theatrical release but it is the ending featured on the Director's Cut DVD.
Oddly enough, the first time I saw the film on cable in the '80s, it showed the Det. Cameron ending (back then, cable didn't have access to director's cuts and what-not, so I have no idea how they managed to secure it). A few years later I caught it on late night TV, and it featured the theatrical "dog" ending.