Health & Fitness

Targeted therapies cut side effects, minimize harm to surrounding tissue

Miami Herald Staff

On Dec. 12, 2011, Javier Areas Jr. was diagnosed with T-cell acute lymphoblastic leukemia.

Like many parents of children with cancer, Javier Areas took to Google to confirm what doctors told him: His son, diagnosed when he was 8, had an estimated survival rate in the low 30 percent range.

But after going through chemotherapy and taking imatinib, a prescription drug used to treat certain types of leukemia, Javier has been in full remission since his diagnosis more than three years ago.

Dr. Ziad Khatib, director of neuro-oncology at Nicklaus Children’s Hospital, formerly Miami Children’s Hospital, said Javier’s treatment falls under new territory, that is, targeted therapy to hone in on cancer cells rather than scattershot chemo. He ended his other treatments last year but is still taking imatinib, marketed as Gleevec, daily.

“We had the dilemma of when should we stop the medication,” he said. In July, doctors will determine whether to change his dosage or stop it altogether.

The goal of targeted therapies is to improve a patient’s prognosis, reducing the side effects and chances of the cancer returning. The basic premise: Harm cancer cells instead of the surrounding tissue.

A genetic mutation, Khatib said, can be turned off like a light switch with targeted therapies.

“Every day, our cells are dividing and mistakes are made, but sometimes the mistakes don’t matter,” said Dr. Pasquale Benedetto, an oncologist at the University of Miami’s Sylvester Comprehensive Cancer Center.

Sometimes, though, the mistakes can turn into cancer, and targeted therapy can turn off the switch.

“Medications aren’t killing the cancer, just making it dormant,” Benedetto said. “They can be lifelong treatments if they work.”

Dr. Steven Olszewski, radiation oncologist at Baptist Health South Florida’s South Miami Hospital, uses tomotherapy, a type of radiation therapy, to lock on to the shape and size of a tumor and attack it with precisely delivered radiation from all angles.

When Baptist Health’s new $400 million Miami Cancer Institute opens in 2016, it will include South Florida’s first proton therapy center. Proton therapy, an advanced form of radiation therapy, is used especially in pediatric cancers, and brain, head and neck tumors. It uses high-energy protons, sub-atomic particles that produce a positive charge, to blast a tumor.

“It has the potential to have significant cost savings because we’re not treating side effects,” Olszewski said.

The three-room center will include one cyclone that generates the proton beam. Large magnets will spin the beam and deliver it to patients using pencil beam scanning, according to John Kerstiens, director of operations for the Miami Cancer Institute Proton-Photon Therapy.

“Protons actually have weight, unlike conventional radiation, so we can control when they stop,” Kerstiens said. “It’s like watching a bottle rocket.”

Kenneth Kent, 88, underwent radiosurgery at Cleveland Clinic Florida three weeks ago for tumors in his liver and lung. His treatment, which has a 70 percent success rate, included five days of targeted radiation. Radiosurgery does not use a knife, but rather high doses of targeted radiation.

Kent was first diagnosed with cancer in 2012 and has been on different treatments on and off since then. While on chemotherapy, he experienced hair loss, fatigue and an upset stomach. With radiosurgery, he hasn’t experienced any side effects.

Dr. John Greskovich, radiation oncologist at Cleveland Clinic, used the Varian Edge radiosurgery system on Kent. Varian Edge, a complex linear accelerator, improves the accuracy of treatment. With a linear accelerator, paths of electrons travel in straight lines to the patient’s tumor. The machine accelerates electrons to create high-energy X-rays, he said.

“The faster the treatment, the less chance of having a geographic miss,” Greskovich said. “And, the rotational correction enables us to rotate the patient to most precisely aim the beam.”

A patient is immobilized in a cast or body mold. Patients with moving tumors — in the liver or lung, for example — hold their breath while doctors deliver the beam.

“We show patients [how to hold their] breath at the right point in the cycle to hit the tumor while it’s frozen, which protects the healthy tissue surrounding it,” he said.

The method is used to treat cancers of the lung, liver, brain and spine. Success rates are as high as 90 percent for patients with lung cancer, according to Greskovich. Varian Edge is used without chemotherapy.

New clinical trials, medications and treatments provide hope for people who have been living with cancer for years.

Laura Mitchell was 29 when she was diagnosed with a rare type of cancer found mostly in young children: neuroblastoma. The first time her cancer came back, it took nine years. The next? Four and a half. After that, one and a half years.

Now, at 47, Mitchell is experiencing her fifth recurrence of this type of cancer.

“I’ve had everything. I’ve done chemotherapy. I’ve done radiation. I’ve done surgery. I’m running low on options,” she said.

After her mother, diagnosed with breast cancer, had genetic testing done, she did, as well. The results showed that she had neuroblastomas with the anaplastic lymphoma kinase (ALK) mutation.

Mitchell started taking crizotinib, marketed as Xalkori, less than a month ago to shut the mutation down. After two months, doctors will rescan.

“I would take whatever side effects there are,” Mitchell said. “This is much more palatable than the chemotherapy I did 18 years ago. The longer I live, the more possibilities are open, which is exciting.”

A glossary of terms

Targeted treatment: Treatment that uses drugs or other therapies to identify and attack specific types of cancer cells with less harm to normal cells. Some targeted therapies block certain enzymes, proteins or other molecules involved cancer cell growth. Other targeted therapies help the immune system kill cancer cells or deliver toxic substances directly to cancer cells. Targeted therapy may have fewer side effects than other types of cancer treatment.

Inhibitors: Drugs that block the growth of cancer cells.

Tomotherapy: A type of radiation aimed at a tumor from many different directions. The patient lies on a table and is moved through a doughnut-shaped machine. The radiation in the machine rotates around the patient in a spiral pattern. Before radiation, a 3D image of the tumor is taken.

Radiosurgery: Newer technology where surgery is performed without a knife. Delivers high doses of radiation precisely to tumors. Varian Edge falls under this.

Proton therapy: Proton therapy is a type of radiation therapy — a treatment that uses high-energy beams to treat tumors.

Sources: Cancer.gov and Mayo Clinic

Related stories from Miami Herald

  Comments