Cancer Cells in Healers’ Sights

“Inoperable lung cancer” is a devastating diagnosis for a patient to hear, but a new treatment called proton beam radiotherapy is beginning to make it less of a death sentence, according to researchers at Loma Linda University Medical Center.

Unlike conventional radiation therapy with X-rays, which causes heavy damage to healthy tissue surrounding the tumor, proton beam therapy delivers virtually all of its energy to the cancer cells themselves, increasing the likelihood of a cure and sharply reducing side effects.

“I think it’s remarkable when I see patients . . . who are incredibly ill [with emphysema] and we can give them something that doesn’t make it worse,” said Dr. David Bush, head investigator of the study. “Many times, the surgeon has told them they can’t do anything, and we’ve got a treatment here that may work. They are obviously pretty happy about it.”

According to the American Cancer Society, almost 157,000 people will die of lung cancer this year--about 28% of all cancer deaths. Most cases are caused by cigarette smoking.

Surgery is the most effective treatment of lung tumors that have not spread outside the chest. Smoking-related illnesses such as coronary artery disease and emphysema, however, often make surgery too risky or even impossible. As many as 20% of lung cancer patients can fall into this category, and they are usually treated with radiation.

Potential side effects of radiation include permanent lung damage, which can leave a patient with a cough or difficulty breathing, as well as heart, esophagus and spinal cord damage. Reducing the occurrence of side effects while increasing the dose of radiation to fight the cancer became a goal of Bush and his colleagues at Loma Linda’s Proton Treatment Center.

“The results [of regular treatment] were not very good because of lung damage and recurrence. That’s what led us to do the trial. This newer type of [proton] treatment could limit the amount of lung damage and also give higher doses to get rid of tumors,” Bush said.

The study, conducted from 1994 to 1998, focused on 37 patients, averaging 72 years of age, with early-stage inoperable lung cancer. Two years after they received proton beam therapy, 63% of the patients were disease-free; among the 27 patients with the smallest tumors, 86% were disease-free. The rate of cancer recurrence after proton therapy was 13%, compared with a rate of 40% to 50% seen with conventional radiation treatment. In most cases, the tumor stopped growing, shrank or disappeared entirely.

Proton therapy differs from conventional radiotherapy primarily in that protons can be controlled to release their DNA-damaging energy exclusively in the area of the tumor. Protons deposit nearly all of their energy at the end of their programmed path, to within one millimeter. Cathy McFarland, a case manager at Loma Linda, calls protons “medical smart bombs” because they hit their target without damaging tissue in front of or behind the tumor.

Higher Doses, Fewer Problems

Perhaps the most promising result of the study is the potential for giving much higher doses of radiation with far fewer side effects and less treatment time. Nineteen study participants had emphysema or smoking-damaged lungs. They received 10 high-dose treatments over a two-week period, instead of weeks of potentially harmful X-ray radiation. After treatment, they showed practically no decrease in lung function.

Higher, more effective doses and less treatment time may be prove to be the payoff in proton therapy.

“By pure physics, it’s better,” said Dr. Les Yanemoto, a radiation oncologist at Loma Linda.

The Proton Treatment Center at Loma Linda is the only facility of its kind in the U.S. Opened in 1990, the center has treated more than 5,000 proton therapy patients. With three whole-body treatment rooms and a fixed-beam source in a fourth room for dealing with tumors of the head, neck and eye, the center can treat more than 100 patients per day.

Proton therapy can successfully treat a variety of other cancers, including prostate and brain tumors. It is also used to treat vascular malformations and macular degeneration, which is the leading cause of blindness for which there is no known cure.

Tumor treatment begins with the use of a CT scan to develop a 3-D computer model of the patient’s tumor and surrounding organs. Then, a particle accelerator is programmed to target the proton beam at the three-dimensional space of the tumor.

Delivered by a “Ferris wheel with a nozzle” that rotates around the patient, the beam can be positioned to send protons anywhere in the body. The painless treatment allows outpatients to be seen in sessions of 20 to 45 minutes.

At least two other cancer centers are building proton treatment facilities. Massachusetts General Hospital hopes to have its facility operating in five or six months. Patients have been getting treatment at a nearby Harvard physics lab.

The hospital’s Dr. Noah Choi found the Loma Linda results “quite encouraging. We are very glad Loma Linda has been able to produce this data.”

The University of Florida Health Science Center also plans to build a treatment center. Like Loma Linda’s, it will be designed by Optivus Technology Inc. of San Bernardino, which has pioneered development of the technology.

Why aren’t more hospitals developing facilities? Sticker shock. To build a treatment center like the one in Loma Linda costs between $50 million and $80 million, said Dennis Valencia, vice president of sales and business development at Optivus.

Though that may seem an unattainable goal for some hospitals, Valencia said it is only a fraction of the estimated $107 billion spent on cancer-related health care each year.

Because proton therapy apparently causes fewer side effects and requires fewer treatments, it has the potential to reduce the cost of cancer treatment worldwide.

Dr. Yanemoto agreed: “The least expensive way to handle cancer is to cure it the first time.”

Medicare and many other insurance plans already cover proton therapy.