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Observational study can’t prove surgery better than more conservative prostate cancer treatment

Thomas Jefferson University

Combo therapy of prostatectomy plus radiotherapy may improve survival in prostate cancer

Our Review Summary

This news release describes an observational study that compared two common “combination” therapies for locally advanced prostate cancer — that is, cancer that is growing but has not spread to other parts of the body. The findings were published in the journal Cancer.

The study showed that a more aggressive treatment option, which involves radiation and surgery to remove the prostate, was linked with a higher survival rate than treatment that consisted of radiation and hormone-blocking therapy without surgery. The news release provided clear data on the scope of the survival differences in the two groups of patients. It also pointed out the serious harms of incontinence and erectile dysfunction associated with prostate surgery.

However, these strengths were offset by a significant omission: the release did not mention a major limitation of the study that prevents us from concluding that more aggressive treatment “may improve survival” as the headline suggests. It also did not address the costs of any of these procedures.


Why This Matters

Questions linger about how to best treat men with high-risk forms of prostate cancer. However, observational data from studies like this one cannot answer the question of which course of treatment is most effective. The problem is that patients and doctors didn’t randomly choose between the different treatment options examined in this study. And there are important factors that may bias these results to favor the surgery group in ways that have nothing to do with the treatment itself. The key thing that this study cannot adequately address is that patients and doctors are more likely to favor surgery in those who can tolerate such an invasive procedure. Irrespective of the cancer, if the patient has other health issues that make surgery more risky, they may choose the more conservative approach. The net effect is the same factors that may lead someone to choose surgery may also mean that they are in better overall health and will simply live longer because of this.

The authors tried to control for these factors by adjusting for reported health issues, but we know that such methods are often insufficient. Only at the end of the release is there mention of other studies that are still to be reported. Those studies are likely randomized trials where the choice of treatment was determined by a flip of the coin. If they show a big difference in survival, THAT will be important. As for the current study, it may suggest a benefit, but it in no way proves that it is due the differences in the treatment itself.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

There was no discussion of the cost of any of these treatments. One survey from 2014 found uninsured patients were charged an average of $34,720 for prostate removal surgery, plus an average of $8,280 for physician costs. Some hospitals provided discounts for prompt payment.

Any comparison between these options could consider not only the costs of the initial treatment but also any subsequent costs associated with side effects or progressive disease.

It’s also worth noting that Jefferson Health offers robotic surgery, which is substantially more expensive.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?


The news release stated the survival difference in clear, absolute terms: “They found that 10 years after treatment, 89 percent of the prostate removal plus radiation group was still alive. That compared with the 74 percent survival at ten years in the group that received only radiation plus hormone therapy, amounting to a 15 percent survival advantage in the group that was treated with prostate removal.”

Does the news release adequately explain/quantify the harms of the intervention?


This was a strength. The release stated: “Men who received the combination of surgery and radiotherapy had higher rates of erectile dysfunction (28 percent vs 20 percent) and higher rates of urinary incontinence (49 percent vs 19 percent).”

The news release also stated: “The risks of prostate removal, or prostatectomy, are well known and include higher chance of developing incontinence and erectile dysfunction. There are some risks associated with radiation treatment and hormone therapy, but they are less common, and are typically thought to have a lower impact on quality of life.”

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

Generally, observational studies — which draw inferences by looking back to see what’s happened in a sample population —  are considered a weaker form of evidence than a randomized clinical trial. That’s because they are more commonly subject to forms of bias such as confounding variables, which can distort the true relationship of the variables under study and make it seem as if there’s a cause-and-effect relationship. (We discussed one of those key variables above in the Why This Matters section.)

As result, the main finding touted in this news release — that patients live longer if treated with the combination of prostate removal and radiation therapy — is not something that can be proved in an observational study.

But this news release did not mention such weaknesses. Instead, it interpreted the result as a definitive finding and put a positive spin on observational data by quoting a researcher who says it “reveals what happens in the real world, rather than the carefully controlled context of a clinical trial.” Only at the end does it mention that future studies may provide additional information, but this cautionary note was inadequate.

Does the news release commit disease-mongering?


The news release did not exaggerate the prevalence of prostate cancer, but it also did not provide data on how common prostate cancer is. In addition, readers may not realize that this finding applies only to some patients with prostate cancer — those with more aggressive appearing disease that falls short of metastatic disease. Most prostate cancer is lower risk. Stating this and providing some context would have helped, but we’ll give the benefit of the doubt here.

Does the news release identify funding sources & disclose conflicts of interest?


The release stated that the study was funded by the New Jersey Health Foundation, the National Cancer Institute, and the Rutgers Cancer Institute of New Jersey Biometrics Shared Resource.

Does the news release compare the new approach with existing alternatives?


The point of the study was to compare two common treatment options, and both are adequately described in the release.

Does the news release establish the availability of the treatment/test/product/procedure?


It’s evident these treatment options are widely available. However, the news release said researchers found many men aren’t getting treatment that’s recommended in medical guidelines.

Does the news release establish the true novelty of the approach?


The news release stated: “For the first time, researchers have shown that more patients live longer if treated with the combination of prostate removal plus radiation therapy.”

It also called this “the largest population-based retrospective study to date” and mentioned that “several large clinical trials” on the topic are nearing completion.

While some of these descriptions tend to inflate the importance of the study, those concerns have been addressed elsewhere.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?


The news release refrains from unjustifiable language except by overselling the findings in the lead, saying researchers “have shown that more patients live longer if treated with the combination of prostate removal plus radiation therapy.” That language implies that those treatments caused patients to live longer even though the study was not capable of showing a cause-and-effect relationship. But since we’ve already addressed that issue elsewhere in the review, we’ll award a satisfactory rating here to avoid docking points twice for the same concern.

Better language was contained in this quote from the researchers: “Our study suggests that removing the prostate followed by adjuvant radiotherapy is associated with greater overall survival in men with prostate cancer.”

Total Score: 8 of 10 Satisfactory

Comments (1)

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Gerald Filardi

October 1, 2018 at 9:52 am

i would hope that most urologists reading this story would not fall into the trap of believing “news releases” and then using that as the basis for further therapy. too many variables to consider when deciding what therapy to choose. Why can’t the media wait until the definitive studies are completed and then report the information???