Can I have an office in my basement without egress?
You'll have to contact your local building department to be sure, but it's very likely that they'll require a second means of egress. They might also have localized information, on ways others in your area have dealt with the problem. It's not likely that you're the only person in your area that's wanted to add living space to their basement.

International Residential Code 2012
Chapter 3 Building Planning
Section 310 Emergency Escape and Rescue Openings
R310.1 Emergency escape and rescue required.
Basements, habitable attics and every sleeping room shall have at least one operable emergency escape and rescue opening. Where basements contain one or more sleeping rooms, emergency egress and rescue openings shall be required in each sleeping room...
...Emergency escape and rescue openings shall open directly into a public way, or to a yard or court that opens to a public way.
Exception: Basements used only to house mechanical equipment and not exceeding total floor area of 200 square feet (18.58 m2).

Based on this code, as soon as a basement is used for more than housing mechanical equipment, egress is required. Though I think most places allow storage and such, and only get picky when a habitable space is added to the basement.
According to the IRC, habitable spaces include any space used for living, sleeping, eating, or cooking.  Non-habitable spaces include bathrooms, toilet rooms, closets, halls, storage and utility spaces, and any similar spaces.
According to Mass.gov, Massachusetts follows International Residential Code 2009 with some amendments. Though it doesn't appear that there are any amendments to the section quoted above.