Steven H. Lin, MD, PhD
Technological advancements in the radiation therapy field, including intensity-modulated radiation therapy (IMRT) and proton therapy, have become a novel and more concentrated approach to delivering radiation doses as well as spare patients from life-threatening toxicities. This direction differs from 3D conformal radiation therapy, which remains the current standard of care for radiation therapy delivery, even with its long-term morbidity and mortality risks.
In an interview with OncLive
, Steven H. Lin, MD, PhD, associate professor of radiation oncology, The University of Texas MD Anderson Cancer Center, discussed why IMRT should be adopted as the new standard approach. He also hones in on the benefits of these advanced radiation technologies, specifically for patients with esophageal cancer.
OncLive: Can you give an overview of your talk on advances in radiation therapy?
: In esophageal cancer management, the most important thing in terms of treatment modality is radiation, along with surgery and chemotherapy. Surgery is still reserved for early-stage cancers; however, for locally advanced diseases, pre-operative chemoradiation followed by surgery is now the current standard of care in patients who are surgical candidates.
For patients who are not surgical candidates, chemoradiation definitively is the standard of care. Radiation is a very important modality for the management of esophageal cancer, however, because of the usual location of esophageal tumors—which is in the chest, surrounded by the heart and lungs—when we deliver the radiation, it’s very important to try and spare the doses to these vital organs as much as possible.
The current standard of care in the community for the delivery of radiation is 3-D conformal radiation therapy, which is simple beam arrangements that deliver higher doses relatively to the heart and lungs. While it delivers cytodoses to the tumor, it unfortunately can potentially have long-term morbidity, as well as mortality, to patients. Not only in the patients who survive long enough from their cancer and then they develop these long-term complications, but also immediately after surgery. More radiation to these structures can potentially increase these post-operative complications.
What advanced technology tries to do is spare the doses as much as possible to these surrounding structures through various ways of delivering the dose, and it modulates the dose so that most of it is concentrated in the tumor, and then relatively low doses go to the heart and lung. IMRT is one way to do it, and certainly for x-ray therapy, it is the most advanced way of delivering x-ray radiation.
Proton therapy is the next most advanced, because it’s not actually x-rays, it’s charged particles, the protons are hydrogen ions that are accelerated and delivered into the patient. By the physical property of charged particles and its interaction with matter, it delivers energy at a very specific point and not beyond that point. Because of the physical nature of protons, it completely spares the surrounding structures while delivering the high dose to the tumor, and relatively no doses are delivered to parts of the heart and lung compared to even IMRT.
What data was looked at in the analysis you performed?
We looked at our experience and compared our complications after surgery and long-term outcomes of patients who were treated between 3-D conformal and IMRT. We found that the use of IMRT does seem to improve and reduce toxicities that patients experience in the immediate surgical period in terms of the incidence of pulmonary complications and gastrointestinal complications, but also long-term outcomes, including cardiac mortality, seem to be spared with the use of IMRT.
We also decided to look in the population data, so we looked at 2,500 or so patients in the database, where a subset of patients got IMRT and the larger group got 3-D conformal.
What we know is the adoption of IMRT was fairly rapid, so we looked at the time period between 2002 and 2009, and we found that at the beginning of 2002, only about 2% of clinicians were using IMRT, and 98% of patients were treated with 3-D. Over time, up to 2009, 30% of patients were being treated with IMRT. That kind of technology is going out to the community and clinicians are believing there is a benefit, of course with not much evidence, but they believe there is a benefit to patients, therefore there is a rapid adoption of that technology.