LOS ANGELES - Weekday mornings, Mona Rosenberg joins a dozen technicians and fellow oncologists in the back room of her clinic to prepare for the day's cancer patients.

They open the patients' files and fire off questions and suggestions about treatment. It's the kind of meeting that could happen in any clinic, but with an important difference: The patients at Rosenberg's Veterinary Cancer Group have four legs.

Mainly dogs and cats come their way, but the practice sees the occasional rabbit or horse at its two Southern California offices.

"We have Moose," Rosenberg said during a recent gathering. "He's a 41/2-year-old chocolate-brown Labrador retriever, and he had a mast [cell] tumor on his scrotum."

Rosenberg, and many others, didn't think this now-routine meeting would have been possible 17 years ago when she opened her practice. But treating animal cancer has become a multimillion-dollar business, and Veterinary Cancer Group has grown with it.

"In the old days it was 'My pet is sick, so let's put it to sleep,' " she said. " . . . [I]f you would have asked me then if it would grow into what it is today, I would have said, 'No way.' "

Veterinary Cancer Group now includes nine oncologists, an acupuncturist, two offices, and resources to perform X-rays, blood tests, surgeries, radiation, chemotherapy, cryotherapy, and immunotherapy on animals. One clinic runs an animal-oncology residency program for veterinarians looking to break in to the specialty.

"Nobody works in isolation here," Rosenberg said. "We get together every morning, all the doctors, all the nurses, the desk person, and we go through every patient we're going to see that day and we give recommendations on what the best thing to do with each patient is."

Treatment methods are similar to those for humans, said Jarred Lyons, a Veterinary Cancer Group radiation oncologist: "We use exactly the same machinery; we use the same procedures. Sometimes that's a surprise to people."

Treatment costs vary from a few hundred to a few thousand dollars, he said, depending on how widespread the cancer is and how long treatment lasts.

A large part of what oncologists do is education-based, Lyons said, to explain treatment options. But pet owners aren't alone in needing education on animal oncology; it's only within the last decade that the subject has become a mandatory part of veterinary school, Lyons said.

"This field is still small and catching on," he said. "I'm one of 65 vet radiation oncologists in the world. But . . . pet owners are smarter and taking better care of their animals, so the demand for us is growing."

Also, pets are living longer as owners take them to the vet more today than they did 20 years ago, Lyons said. Cancer is the leading cause of death among cats and dogs older than 10 years, he said.

"With us it's really about the quality of the life," he said. "A lot of what we do is geared toward not making the animal sick. We don't want to make the treatment worse than the disease itself, and it's what you're willing to put your pet through."

Often, treating pet cancer doesn't mean curing it but extending how much time a dog or cat has left, Lyons said.

"We have that option of letting our animals go, and sometimes that's the best thing to let them go. But we can almost always let them live longer and with dignity and comfort so they don't even realize they are sick.

"On a human level, that's not really an option," he said. "We don't want to let people go, so we put ourselves through a lot more pain because there is a difference in the way we view our lives and the way a pet's life is viewed."

Challenging preconceived notions of cancer treatment also is part of the job. When Jim and Faith Pickett brought Moose to the clinic after his tumor was removed, the couple had many questions. But they were sure of one thing.

"We always said we wouldn't do chemo with Moose," Faith Pickett said. "We don't want to put our dog through all that pain."

Rosenberg told the Picketts that dogs' and cats' reactions to cancer treatments often are very different from people's. Humans often become sick and lose weight during chemo, whereas only 15 percent of dogs and 10 percent of cats suffer such side effects.

"Psychologically, animals aren't dealing with the same baggage that we deal with when we go through cancer treatment," Rosenberg said. "They start in a much better space than we do, and nobody's telling them that they're going to get horribly sick so they don't talk themselves into some of the things we do."

After a battery of tests, the clinic found no signs of cancer. But Rosenberg warned that free-floating cancer cells could be loose in Moose's body, advising chemotherapy as a way to eliminate whatever might be left. After going back to their primary-care vet for a second opinion, the Picketts took Rosenberg's advice. Moose recently began a six-month chemotherapy treatment, Faith Pickett said, with no side effects so far.

"Our dogs - they're family and we have to do the best we can to make sure they have the best lives possible," she said. "So we decided that it's worth the risk."