This news release describes five-year outcomes for 309 men with early-stage prostate cancer who received stereotactic body radiation therapy (SBRT), which delivers targeted doses of radiation cheaper and faster than the prevailing radiation therapy treatment for prostate cancer. The study measured the rates of severe injury to surrounding tissues and disease-free survival.
The news release said it’s the first large, multi-institutional study of this technology in prostate cancer with long-term follow-up, involving patients at 21 community, regional, and academic hospitals across the U.S. The release does a good job of quantifying the evidence but could have helped readers better understand the implications of the data by giving cost and safety comparisons with other radiation treatment, and by discussing limitations related to using a historical control group (rather than a contemporaneous control group) which introduces potential for bias.
The release is based on a study presented at the American Society for Radiation Oncology (ASTRO) annual conference. The study abstract can be found on page 4 of this document.
Prostate cancer is a commonly diagnosed condition in men that is associated with aging. Many patients don’t realize that prostate cancer is not a uniformly fatal disease. For men with low risk disease, active surveillance without treatment is a viable option. Even for men with higher risk disease where treatment is warranted, one needs to follow patients for 10-15 years to identify a survival benefit from treatment. This is useful context to keep in mind when examining this new study of patients with low and intermediate risk prostate cancer. The results present a rosy picture of SBRT, in terms of both benefits and harms. However, without a contemporaneous control group, such as those receiving intensity-modulated radiation therapy (IMRT) or even active surveillance, one cannot be sure that these favorable results are due to the treatment itself or the patients who were selected for treatment. Comparing results of individuals who are likely to live a long time with their disease to those treated at some point in the past is rife with problems and such studies, called case series, are deemed to be low on the ladder of scientific rigor. Even the low rate of complications, while very reassuring, still would benefit from a comparison to patients treated with other forms of radiation at the same time period.
The news release quotes lead researcher Robert Meier, MD, saying previous studies have shown SBRT to be “a cost-effective and faster alternative to IMRT” but does not provide any detail as to the specific costs of either procedure. In fact, the difference is substantial. A 2014 study in the Journal of Clinical Oncology examined Medicare claims data showed a mean treatment cost of $13,645 for SBRT versus $21,023 for IMRT. And a 2012 study in the Journal of Oncology Practice concluded that SRBT has “great potential cost savings” for the health care system, with an average cost of $22,152 versus $35,431 for IMRT.
One could also consider the cost of side effects as well as need for future treatments.
The news release gives a lot of data. It states that 97 percent of patients were free from prostate cancer progression after five years, exceeding a historical control of 93 percent. It also says that fewer than 2 percent of patients experienced severe toxicities in their gastrointestinal, reproductive, and urinary systems, and no patients reported life-threatening or fatal toxicity. However, the news release does not attempt to say how these rates compare with other treatment options, which would help readers put the data in perspective. There are important caveats left out in the description of findings that are discussed under the evidence criterion.
The news release states that between half and two-thirds of patients experienced low, “usually temporary” rates of toxicities. It also notes that “fewer than 2 percent of patients experienced severe toxicities in their gastrointestinal, reproductive, and urinary systems, and no patients reported life-threatening or fatal toxicity.” A few more details here would be helpful. For example, how many patients experienced a decline in urinary or sexual function, and for what period of time? And what are other potential risks of radiation therapy? The real question is how do these harms compare to other treatments? That was not assessed in this study.
The news release gives some details to help readers understand how the study was conducted. However, it neglects to include several key points. First, the patients enrolled are from a very low risk population in terms of measuring benefit. The statement that these results compare favorably to historical controls at 5 years misses the point that the risk of death for this patient population isn’t seen until 10-15 years at the earliest. Second, without a contemporaneous comparison group, it should be stated that these results are subject to misinterpretation — both in terms of benefits, which are likely to be equally good with almost any other treatment (and some would argue active surveillance without treatment), and harms. Finally, it isn’t clear who this population represents. If these are younger men in their 50s and 60s, side effects are important but the long-term efficacy (beyond 5 years) is critical. If the men are over 70, one can argue whether they needed to treat the low risk group at all. In summary, this is a case series with no contemporaneous comparison group among a population with low risk prostate cancer where 5 year follow-up is inadequate to say that the treatment was successful in preventing progressive disease.
The release could have included some cautions that the lead researcher discussed in a published paper in 2015. For example, he states that more radiation effects on adjacent organs might be observed after longer follow-up, and “firm conclusions about the efficacy and toxicity of SBRT relative to more conventional approaches await scrutiny by prospective randomized trials.”
The news release does not commit mongering. However, as noted above, the patients enrolled in the trial were a very low risk population and one could argue that some of these patients may not have needed treatment at all.
The news release does not say how the study was funded or whether any of the investigators have conflicts of interest. In papers on the topic published in 2015, the researchers declared no conflicts of interest.
Some of the men in the study had a low-risk form of prostate cancer, which might have made them eligible for active surveillance rather than surgery. That option is not discussed in the news release. As mentioned in the quantifying benefits section, the news release does mention that this type of radiotherapy was compared with standard radiotherapy, although it was not directly studied.
The news release states that patients in the trial were treated at 21 academic, regional, and community medical centers, which suggests that SRBT is widely available.
The release claims novelty with this statement: “Our study is the first to contribute multi-center data that support the use of SBRT as front-line therapy for men with prostate cancer.” But it also states that SRBT for prostate cancer has been studied at other institutions, and that the procedure has become a standard of care for some lung cancer cases. It does not claim that this is a novel procedure.
The news release does not contain any unjustifiable or sensational language. But as noted above, the favorable results in terms of benefit are not surprising and attributing them to the treatment could be viewed as unjustified.