Clinical trials of NDV have been done but have not proven that NDV is effective as a cancer treatment. Some of the trials reported positive results and some did not. Most of the studies enrolled only small numbers of patients who also received standard treatments. None of the trials published in English were randomized and few were controlled. Randomized clinical trials give the highest level of evidence. In randomized trials, volunteers are assigned randomly (by chance) to one of 2 or more groups that compare different factors related to the treatment. In a controlled clinical trial, one group (called the control group) does not receive the new treatment being studied. The control group is then compared to the groups that receive the new treatment, to see if the new treatment works. Randomized controlled trials, enrolling larger numbers of people, are needed to confirm the results of studies done so far on the use of NDV to treat cancer.
Clinical trials studying the use of NDV as a cancer treatment have been done in the United States, Germany, and Hungary. Below are brief descriptions of these studies.
Studies Using Oncolysate Vaccines
Four clinical trials in the United States studied the use of NDV oncolysates in patients with metastatic melanoma. Three of these studies, a phase I clinical trial and 2 phase II clinical trials, were by the same group of researchers. Some positive results were found in these studies. The fourth trial was led by different researchers and showed no benefit. The same type of NDV was used to make the vaccines in all 4 studies, but the 2 groups of researchers used different methods to make them. Results from these studies need to be confirmed by randomized controlled trials that enroll larger numbers of people.
Two other phase II trials of NDV oncolysates were done in Germany. One of the studies showed that people in the trial had longer disease-free survival when compared with published information on similar patients who were treated with surgery alone. Because these studies were not controlled and the patients received other treatments, it is not clear if it was the treatment with NDV oncolysates that caused the responses reported.
Studies Using Whole-cell Vaccines
All published clinical studies of whole-cell vaccines with NDV have been done in Germany. Most of these studies involved patients with colorectal cancer, breast cancer, ovarian cancer, or renal cell (kidney) cancer. The same type of NDV was used to make the vaccines in all of the studies.
Some of these studies found improved disease-free survival or improved overall survival in patients treated with whole-cell vaccines. The lack of control groups and other weaknesses in study design and reporting made it unclear if benefits were caused by the whole-cell vaccine or by something else. Overall, the results showed that these vaccines may help the immune system kill more cancer cells during the vaccination program but may not provide long-term cancer immunity.
Studies Involving Infection with NDV (Including MTH-68)
Most research on the treatment of cancer by infecting patients with NDV has been done in Hungary, using the NDV strain MTH-68. The published findings include the following types of studies:
- An anecdotal report (incomplete descriptions of the medical and treatment history of one or more patients).
- A case report (a detailed report of the diagnosis, treatment, and follow-up of an individual patient).
- A small case series (a group of case reports involving patients who were given similar treatment).
- A phase II clinical trial.
According to the researchers, the MTH-68 treatment was helpful for most of the patients in these studies. The number of patients in the studies was small, however, and the patients in the clinical trial were not randomly assigned. The patients also received other treatments. For these reasons, it is not known if the patients were helped by the MTH-68 or by something else.
In the United States, a phase I clinical trial tested PV701, another type of NDV. In this trial, 79 patients with advanced cancers that were not helped by conventional therapy were given PV701 by injection into a vein. Some patients had partial responses to the treatment, while others did not have any change in their condition. More studies are planned.
One major concern is that repeated injections of NDV may cause a person's immune system to form antibodies against the virus. These antibodies would prevent NDV from infecting and killing cancer cells. More research is needed to study this.