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Are bacteria useful as cancer ‘weapons,’ or far too early to know? Key context missing from HealthDay story


2 Star



Doctors Use Bacteria as Weapon Against Cancer

Our Review Summary

This story reports about a safety trial involving 24 cancer patients in which a weakened form of the bacterium clostridium novyi was injected into tumors. The results were presented at the International Cancer Immunotherapy Conference.

The story provides appropriately cautions about potential harms. But it explained the results of the study in a way that may cause confusion, among other issues.


Why This Matters

Harnessing bacteria to attack cancer tumors isn’t a new idea, but it’s been gaining interest due to technology that can develop bacterial strains that have fewer side effects and greater therapeutic potential.

Yet news stories about early trials like this one should be careful not to provide false hope. In this story, the message that the bacterium “appears to target malignant cells and could provide a new means of fighting cancer” is overly optimistic, given that this is a study that was designed to establish a safe dosage level, not show whether there’s a meaningful clinical benefit.


Does the story adequately discuss the costs of the intervention?

Not Satisfactory

There was no discussion of the potential cost of this therapy. Although it is probably too early in the process to discuss precise numbers, it would have been helpful if the story had discussed the big picture. While bacterial therapies may be cheap to develop, the cost of clinical trials and bringing a new product to market tend to be very high. Also, an ongoing trial pairs this therapy with immunotherapy drug pembrolizumab, which can cost about $13,500 per month, according to published reports.


Not Satisfactory

The story did provide some specific numbers on the scope of the benefit, but we found the wording confusing and unclear:

The bacteria germinated in the cancers of 11 out of the 24 patients, with tumor cells dying off as a result.

Tumor shrinkage of greater than 10 percent was observed in 23 percent of patients. However, Janku said this could be an underestimate since the infection causes surrounding tissue to become inflamed, making the lesion appear larger than it actually is.

Following bacterial therapy, cancer stabilized in 21 patients. When both injected and uninjected lesions were included, the stable disease rate was 86 percent, the researchers reported.

Did the tumor shrinkage occur in 23% of the 24 patients in trial, or the 11 patients in which the bacteria “germinated?” It appears to be the latter, meaning it’s an even tinier subset of patients who had tumor shrinkage greater than 10 percent–just about 3 patients. (The story also could have explained why researchers picked 10 percent as a measuring point for tumor shrinkage. It did explain that the therapy could have caused inflammation that made the tumors harder to measure.)

Based on the next sentence–that 21 out of 24 patients had unchanged cancer–the story would have been more clear had it simply explained that most tumors neither significantly grew nor significantly shrunk after the therapy. Also, it’s not clear when these measurements were taken–if this was after a year, it seems notable that the majority had stable tumors. But if they measured tumors after just one week, it’s not very surprising.

Context is also lacking–we don’t know the cancer stage, what is considered a “clinically important” tumor shrinkage, and how the observed shrinkage compares with current treatments. Lastly, all of this needs to be taken into consideration with the fact that there was no control group to compare these results against.



The story mentioned that two patients in the trial who received the highest doses fell ill with sepsis and gangrene. It also mentioned a need to “keep an eye on potential side effects” in future trials.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

We like that the the story called this “a small, preliminary study” in the second paragraph, and cautioned at the end: “Research presented at meetings should be considered preliminary until published in a peer-reviewed journal.”

But the story also should have spelled out for readers that the “clinically meaningful activity” in terms of tumor shrinkage, cited by a researcher, does not necessarily translate to curing or even stalling cancer. Also, the intent of this trial was to demonstrate safety; it could not prove that the therapy has a benefit. And, importantly, there was no control group.

Does the story commit disease-mongering?


The story does not engage in disease-mongering. It would have been helpful to discuss how many people have sarcomas, the type of cancer most patients in the trial had. According to the Sarcoma Alliance, there are about 15,000 new cases diagnosed annually in the U.S. There are also over 90,000 new cases of melanoma diagnosed annually.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

The story quoted two researchers who were involved in the trial, with no independent sources. It did not say that the trial was sponsored by a company called BioMed Valley Discoveries.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

The story mentioned “classic immunotherapy” as not seeming to work for most sarcomas, which are cancers that arise in connective tissue such as fat, muscle, and bone. However, it did not mention other treatment options such as radiation, surgery, or chemotherapy.

As a side note, most immunotherapies are very new–with still-emerging side effects and unknown long-term benefits–so we take issue with framing immunotherapy as “classic.” Standard is perhaps a more accurate word.



The story makes it clear that researchers are still studying this approach, implying it’s not available widely.

Does the story establish the true novelty of the approach?

Not Satisfactory

The story does not establish the novelty of the research. The abstract describes this as a “first-in-man” trial of weakened clostridium novyi spores in cancer patients.

In general, though, bacterial therapies for cancer tumors have been studied for decades, although only recently have safer forms been available.



The story does not appear to rely solely on a news release.

Total Score: 4 of 10 Satisfactory

