ABC News’ Matthew Jaffe reports: UPDATE: A Wyden spokesman says he will vote this weekend if there is a vote on a repealing the military's policy toward gays serving openly in the military. The senator already has us working on a DADT speech for him tomorrow. If the vote is this weekend, he is determined not to miss it," she said. Our earlier post: Sen. Ron Wyden, D-OR, announced today that he will undergo surgery on Monday for prostate cancer and will not return to the Senate until January, an absence that could complicate Democratic efforts to pass an array of key issues. Wyden said he was diagnosed with early-stage prostate cancer in late November after his annual physical. The surgery will be performed on Monday at Johns Hopkins Hospital by Dr. Alan Partin, Wyden said. “Thanks to routine screening, this was diagnosed early and I expect a full and speedy recovery,” Wyden said in a statement. “I scheduled the surgery for the Monday before Christmas anticipating that the Senate would have recessed by that time and that there would be no disruption to my work in Oregon or Washington. However, it now appears that I will be missing votes tomorrow and possibly next week while I prepare and undergo this procedure. I expect to be back to work full-time when the Senate reconvenes in January.” “If anything is taken from my experience, I hope it is the importance of getting routine physicals,” he said. “One in six men will be diagnosed with prostate cancer during their lifetimes. Early detection is critical to catching this disease when treatment is most effective.” In a strictly – and callously – political sense, Wyden’s absence from the Senate for the remainder of this year could prove problematic for Democrats, who are set to take up a slew of high-profile measures where every vote will likely be crucial. In the Senate – where partisan rhetoric has escalated in recent days as the end of the lame-duck session approaches – Democrats are expected to need every vote they can get on the START treaty, the omnibus spending bill, the Don’t Ask Don’t Tell repeal, and more.