Head and neck tumors are some of the most difficult cancers to treat. Often during radiotherapy treatment, the salivary glands are damaged or destroyed. Patients then must live with constant dry mouth with the lack of saliva leading to massive oral problems. But a change in radiotherapy may help preserve vital tissue near tumors in millions of cancer patients all over the country.
By combining three existing technologies into one therapy, known as tomotherapy, Dr. Thomas Mackie, professor of medical physics and human oncology at UW-Madison, has created a new needle for delivering radiation that will hit more cancer cells and avoid healthy tissue. These technologies are the linear accelerator, a radiation therapy machine; helical computed tomography, a CT imaging machine used to get cross-sectional images of the patients; and faster computers.
A linear accelerator is attached to a helical CT scanner that travels 360 degrees around the patient while delivering radiation. Fastened to the linear accelerator is a multileaf collimator, or MLC, that shapes the radiation beam as it moves around the patient. The MLC has several teeth that open and shut, modifying the beam to the shape of the tumor, like an ink-jet printer spitting out ink in the shape of a letter.
Attaching a CT scanner will enable doctors to see the treatment progression and account for body movement during therapy. Imaging the patient once at the beginning of treatment does not mean the person will be the same after seven weeks of treatment, Mackie said.
The more doctors know about where the cancer is in a patient's body, the more likely that radiation will hit cancer cells versus healthy tissue.
\For the first time we can image a patient while they are being treated,"" Mackie said. "" We can pinpoint where the tumor is and guarantee we are going to be able to go back to the same spot and zap it again.""
Getting an image of the tumor throughout treatment is not the only innovation. Detectors have been placed all around the machine that measure the dose of radiation a patient receives.
""Without fast computers, this wouldn't be possible,"" Mackie said. ""My whole career is based on asking what can't we do today that we would like to do? That's where we do research. Because computers will get faster, and by that time we will have written the software and developed the processes.""
Most of the technology used in tomotherapy has already been used separately for treating cancer, so clinical trials were not needed for obtaining FDA approval to market and sell the machine.
Dogs are great models for human cancer. ""Like humans, dogs get spontaneous cancer,"" said Dr. Linda Forrester from the radiation oncology department at the UW-Madison Veterinary School, who is working with Mackie to develop tomotherapy for the animal world.
Scooter, a golden retriever with cancer in the nasal cavity, was the first tomotherapy patient. The treatment of choice for nasal cancer is radiotherapy. The problem in treating nasal cancer is it is so close to sensitive tissue like the eyes, said Forrester. Treatment will often cause blindness.
Scooter's treatment compared a traditional diagnostic CT scan to the CT scan generated by the linear accelerator. Since the linear accelerator uses more energy than the diagnostic scan, the traditional scans do not show as much detail.
""But they were good enough so that we could see the tumor and see the bony destruction,"" Forrester said. ""It was excellent for verification. If we were to treat the dog, we were comfortable to say the dog was in the position we wanted it to be.""
The first tomotherapy unit was installed at UW-Madison in January 2001, and more units are being installed in Canada.
""By the end of the year there will be five or six sites,"" Mackie said. ""In 10 years, I predict this is how radiation will be done for most places.""
The goal in radiotherapy is not only to cure the cancer, but also to improve the quality of life. If doctors are able to treat head and neck cancer without affecting the saliva glands, then a patient's quality of life will improve greatly.
