Here are some ways to refer to it, depending on the context:
* If referring to the city in Massachusetts: You can simply use "Worcester" as it is, as English words are often used in French, especially when referring to proper nouns.
* If referring to the city in England: You can use the French spelling of the city's name, which is "Worcestre".
* If referring to Worcestershire sauce: It would be translated directly as "Sauce Worcestershire".
Ultimately, the best way to spell it depends on the context and your desired level of formality.