PORTLAND — Newly inaugurated Mayor Michael Brennan, who underwent surgery to remove a cancerous tumor on Christmas Eve, hopes to return to a light work schedule this week at City Hall, and a full-time schedule in the not-too-distant future, he said.

Brennan, 58, who is often seen running along Portland’s streets and trails, was caught by surprise by the cancer diagnosis last month.

“I was shocked and devastated,” Brennan said. “I’ve never smoked, never drank, I exercise, I eat relatively well. I tried to go through every potential cause, and they weren’t there.”

Brennan began experiencing painful stomach cramps the week of his Dec. 5 inauguration.

Maybe it’s nerves, Brennan thought. Maybe it’s excitement.

But on Dec. 15, with Brennan still feeling the cramps, his wife convinced him to see a doctor. The doctor delivered bad news: Brennan, the city’s first popularly elected mayor since 1923, had cancer.

The following day, Brennan underwent a CT scan with inconclusive results. Doctors still couldn’t determine what type of cancer he had.

On Dec. 23, he had a colonoscopy, which located the tumor in his small intestine. But seven days after the diagnosis, Brennan still didn’t know anything about his short- and long-term fate.

On Dec. 24, Brennan had surgery at Maine Medical Center to remove the tumor. After studying a tissue sample, doctors determined his tumor was carcinoid, an extremely slow-moving and treatable form of cancer, he said.

The diagnosis brought relief. As long as Brennan gets monthly shots, his doctors said, the cancer likely won’t spread. It won’t be eradicated either — chemotherapy and radiation have little effect on carcinoid tumors — but he should be able to live with the cancer without any symptoms.

“Sometimes, people live with carcinoid tumors for 10, 15 years and don’t even know it,” Brennan said. “It’s one of the best types of cancer you can get, if you’re going to get cancer.”

The initial diagnosis caught his friends, family and colleagues off-guard. But all expressed optimism. His wife, Joan, said Brennan was only in bad spirits because he couldn’t do his typical 4-mile run.

Brennan feels side effects, he said, but mostly from the surgery, not the cancer. He gained 10 pounds in the hospital from fluids and rapidly lost it again, which has affected his energy.

The tumor and surgery also sapped his appetite.

He’s gone on 1-mile walks with his wife, and hopes to resume his 4-mile runs next month.

He said his personal tale appears to have a happy ending, but shows the need for all Mainers to have access to affordable health insurance like he does.

“I was able to see a general practitioner, an oncologist and have surgery in less than two weeks,” he said. “Not everybody would be so lucky. That’s a major concern for me.”

Jason Singer can be contacted at 791-6437 or at:

jsinger@pressherald.com