Sen. John McCain returned to the U.S. Senate on Tuesday, 10 days after recovering from surgery to remove a malignant brain tumor. The Republican senator from Arizona is back in Washington to work on health care reform after undergoing minimally invasive surgery for an aggressive glioblastoma, a quick return after spending the past week outdoors and hiking with his daughter Meghan and friends. McCain was in the Senate on Tuesday afternoon, in time for a critical vote on health care. But is the 80-year-old senator risking his health by getting on a plane or returning to work too soon? "It is possible to fly cross country safely, but it needs to be done carefully," said NBC News medical correspondent Dr. John Torres. "Having a trained flight crew and medical team that fully understands how flying can stress the body and worsen the medical condition is key." Sen. John McCain, R-Ariz., and Joe Harper sit on a rock at Zebra Falls in Oak Creek, Arizona in a photo shared on Twitter on July 23, 2017. John McCain / via Twitter McCain is still in the "honeymoon" phase of his medical care, meaning he’s in the pre-chemotherapy and pre-radiation stages of care when fatigue and side effects are more likely to happen. But he is at higher risk of developing a deep vein thrombosis during the flight, according to Dr. Steven Kalkanis, chairman of the department of neurosurgery at the Henry Ford Health System, one of the most respected cancer centers in the U.S. Cancer, which often causes a person's blood to clot more easily, places patients at high risk for developing clots in the legs where blood flow is more stagnant. If the clot dislodges and travels to the lungs, causing a pulmonary embolus or the blocking of air and blood flow in the lungs, the results could be deadly. "Cramped quarters, lack of movement, dehydration, and the hypercoagulability of brain tumor patients definitely increases the risks of these complications occurring, but they can be mitigated by moving about the cabin and staying hydrated,” said Dr. Lynne Taylor, neuro-oncologist and co-director of the Alvord Brain Tumor Center at University of Washington. "Still, the risk of DVT in brain tumor patients is high