Sen. Arlen Specter has been diagnosed with a recurrence of Hodgkin's disease, a cancer of the lymph system for which he was treated three years ago.

In a statement released yesterday, Pennsylvania's senior U.S. senator said the recurrence was detected during a routine scan of his chest and abdomen. A biopsy confirmed that the cancer had returned in a chest lymph node.

Just last month, Specter talked about beating the disease as he promoted his new book, Never Give In: Battling Cancer in the Senate.

In yesterday's statement, Specter said he was surprised by the relapse because he'd had no symptoms - unlike in 2005, when crushing fatigue and other symptoms led to the diagnosis of stage IVB Hodgkin's disease.

This time, his stage is considered IIIA, which is "significantly less advanced," according to the statement from Specter's office.

His family received the news with the same stoic resolve that the senator has shown in the past, his son, Shanin, wrote in an e-mail last night.

"He simply views this as a hurdle to jump over. . . . As for the rest of us, we've been through this with him before, and we've fortunately inherited his resolve and that of my mother."

His father, Shanin Specter wrote, "has literally written the book on how to deal with cancer, so he is well-prepared for the experience." The senator is to start outpatient chemotherapy treatment next week, according to his son.

The indefatigable senator was in Philadelphia over the weekend but didn't stay long.

"I was with him Sunday in Philadelphia and have talked to him as recently as late this afternoon by phone," his son wrote. "He's in Washington, working - what do [you] expect?"

University of Pennsylvania oncologist John H. Glick, who treated Specter in 2005, said in the statement that the senator "has an excellent chance of again achieving a complete remission."

The five-year survival rate for patients like him is 60 percent. Glick also noted that at 78, Specter is in excellent physical condition, plays squash regularly, and follows a careful diet.

Specter is to undergo a 12-week chemotherapy regimen developed at Stanford University. Seven drugs are administered over a shorter period, but more frequently, than standard chemotherapy regimens.

He said he expected to continue working during treatment, as he did the first time around.

"I look forward to continuing our joint efforts across a wide variety of issues in the Senate," Sen. Bob Casey, a Democrat, said in a statement released yesterday.

"I have no doubt that Arlen will confront his health challenge with the same courage and determination that has marked his previous battles," Casey said. "My thoughts and prayers are with Arlen and his family."

Specter underwent surgery to remove a benign brain tumor in 1993; it recurred in 1996 and was successfully treated. He also had coronary bypass surgery in 1998.

"I consider this just another bump on the road to a successful recovery from Hodgkin's, from which I've been symptom-free for three years," Specter said in the statement. "I've beaten some tough medical problems and tough political opponents and I expect to beat this, too."