ASTRO 2015
Can SBRT be of use for early, operable non-small cell lung cancer?
Dr Joe Chang – University of Texas MD Anderson Cancer Center, Houston, USA
Can you give us an overview of Stereotactic Radiation Therapy?
Stereotactic radiation therapy is a new technology which focuses on lung cancer so we have many, many radiation beams focussed to the target which is a cancer and it delivers a very high biological dose, typically higher than 100Gy, to the target. In the meantime we use imaging guidance to avoid the surrounding critical structure therefore the dose to the surrounding tissues is lower. So, instead of delivering thirty treatments for the whole treatment course we only need five, less than five, or ten fractions of radiation therapy. So we deliver in a much shorter period of time but a much higher biological dose. What it does is it can improve the local control rate up to 95% above but with minimal toxicity.
How new is this form of radiation therapy?
It’s not brand new, we already treated, for example, for stereotactic radiation therapy for lung cancer for a decade but it was not there at the time when I was a resident. So it’s the past decade treatment but the outcomes are so promising that it’s considered as a milestone for lung cancer treatment using stereotactic radiation therapy.
How is SBRT currently used and how are you using it in your research?
Currently it’s being used for medically inoperable early stage lung cancer, that has been the standard treatment for lung cancer now in the United States and also in most of the world. Currently a research project is working on whether we can extend the indication from medical inoperable to medical operable which means conventionally that is surgical resection but now we are talking about whether we can do stereotactic radiation therapy for those patients who are operable.
Could SBRT replace surgery in some patients with early NSCLC?
Obviously at this moment we just published a randomised study in Lancet Oncology this year that shows, in fact, the survival is better; stereotactic radiation therapy is better than surgical resection although the patient numbers are still low so we need a bigger randomised study. So at this moment I would not say it should replace surgery but I would say it’s an option for patients who are willing to consider it, particularly for people who have other comorbidities or who is very aging in terms of their age. As you know, lung cancer the median age is 70 years old at their time of diagnosis and most of them are smokers and most of them are male. For males in the United States the life expectancy is 76 years old so we have a six year window to do it. So surgical resection is a big challenge for most of these patients.
What are some of the key points of the talk you are giving at ASTRO 2015?
The key point I want to make is that stereotactic radiation therapy should be considered as an option for patients who are operable for early stage lung cancer, that’s one message. The second message is that the indication of stereotactic radiation therapy now is extended from stage 1 to stage 4 for patients with oligometastatic disease. For this group of people, some of them may potentially be curable or with more durable local control with prolonged survival with local treatment. So we’ll talk about oligomets treated with stereotactic radiation therapy; we’re going to talk about quality of life, because this group of people will survive for many, many years so the quality of life will be important. And we can talk about if they recur where they recur, why, how and when? So in that case to help us to guide for the future. In addition, for the future of the research combining stereotactic radiation therapy with immunotherapy like PDL-1 antibodies or CTLA-4 antibodies, that is a new research direction because what we believe is that the high dose radiation therapy delivered in a very short period of time kills the cancer cell, the cancer has died but the cancer is inside your body. Radiation therapy changes antigens on the surface of the cancer and presented to the dendritic cell and presented to the T-cell it can stimulate an immune response. So the cancer killed inside the body stays inside the body may function as a vaccine inside the body or a vaccine in situ. So that way we can provide another unique way to add immunotherapy using the current PD-1 antibody or CTLA-4 antibody added to this. That may further improve clinical outcomes for patients with early stage lung cancer or even for stage 4 lung cancer.
What research are you doing in this area?
The next step is we can get to the patient with early stage lung cancer and then treat it with stereotactic radiation therapy, that is the standard control arm, another arm will be added immunotherapy. So we will see whether the recurrence, local recurrence, regional recurrence, distant recurrence, whether we can further reduce recurrence or even death. So that’s the future. And also for patients who are treated with oligomets currently treated with stereotactic radiation therapy the next step will be stereotactic radiation therapy for oligomeets plus/minus immunotherapy. That will be the future research direction.
Any final highlights?
Stereotactic radiation therapy started with lung cancer but doesn’t need to be limited to lung cancer only. Several other cancers can be used to use stereotactic radiation therapy, for example hepatocellular carcinoma is a localised disease, for early stage hepatocellular carcinoma; pancreatic cancer it can be used and also other recurrent or spine cancer, recurrent cancer, is an indication for stereotactic radiation therapy is getting more and more wider than before. So they’re excited about this.
