It's possible that this film is:
* An obscure film: It may be a low-budget film with limited distribution or a regional production.
* A different title: The title "Sedici anni" might be a translation or an alternate title.
To find the cast, you could try:
* Searching for alternative titles: See if the film is listed under a different name in Italian or English.
* Using specialized databases: Explore specialized databases for Italian cinema or independent films.
* Checking film archives: Contact film archives in Italy for information about the film.
* Searching for film festivals: The film may have been screened at a film festival, and you might find information about the cast on the festival's website.
Let me know if you have more information about the film, such as the director or genre, and I can try to help you find the cast.