James Van Der Beek has cancelled his appearance at a Dawson's Creek reunion event. The actor shared on Instagram that he won't be at Monday's event, a reunion featuring Katie Holmes, Joshua Jackson and Michelle Williams staged to raise cash for F Cancer in light of Van Der Beek's stage 3 colorectal cancer diagnosis. "This is the evening I'd been looking forward to MOST since my angel Michelle Williams said she was putting it together, way back in January," he began his post. "So you can imagine how gutted I was when two stomach viruses conspired to knock me out of commission and keep me grounded at the worst possible moment. "Despite every effort, I won't get to be there. I won't get to stand on that stage and thank every soul in the theatre for showing up for me, and against cancer, when I needed it most." He shared that the role of Dawson will instead be played by Lin-Manuel Miranda. Ending his post on an upbeat note, Van Der Beek wrote, "Everyone please enjoy all the love in that room. Shine some on my family. I will be beaming and receiving from afar in a bed in Austin." The show will go on at New York City's Richard Rogers Theatre.