The researchers who conducted this study concluded that the results demonstrated improved disease-free survival for the study subjects in comparison with survival data published in the scientific literature for similar patients who were treated with surgery alone.[8,12] Because this study was uncontrolled, however, it is not clear whether the improvement in disease-free survival was due to chance alone, to oncolysate therapy alone, to cytokine therapy alone, or to the combination of oncolysate therapy and cytokine therapy.
The same research group conducted a parallel investigation in which immune system responses to combination oncolysate and cytokine therapy were measured in 38 patients who had advanced renal cell carcinoma. In this parallel study, responses to NDV antigens (i.e., the production of anti-NDV antibodies) and transient increases in blood levels of the cytokines interferon-alpha, interferon-gamma, and tumor necrosis factor (TNF)-alpha were found, but responses thought to be important to effective antitumor immunity (i.e., the production of antibodies against tumor-specific antigens, increases in natural killer (NK) cell activity, and increases in blood levels of helper T cells [i.e., CD4 antigen–positive cells] and cytotoxic T cells [i.e., CD8 antigen–positive cells]) were not.
The phase II study of NDV oncolysates in patients with metastatic breast or metastatic ovarian cancer was described by its investigators as a study of autologous, whole cell vaccines.[5,7] The lytic strain Italien, however, was used in this study, so it is likely that immune system responses in the treated patients were stimulated by cellular fragments rather than by intact cancer cells.
In the study, 22 patients were vaccinated by intradermal injection at least 3 times during a 6- to 8-week period that began 2 weeks after surgery to remove malignant cells (either primary tumor cells or metastatic tumor cells). The patients also received intravenous injections of cyclophosphamide, high-dose recombinant interleukin-2, and autologous lymphocytes that had been simulated in vitro by treatment with interleukin-2. The cyclophosphamide was administered to block the activity of a class of T cells (i.e., suppressor T cells) that might weaken the desired immune responses. On average, the patients were followed for a period of 23 months from the time of surgery. Nine patients were reported to have either a complete response or a partial response after vaccine therapy. Five patients had stable disease, and eight had progressive disease. The average duration of response was 5 months, after which disease progression was again observed. Blood samples taken from the patients during therapy showed increases in the numbers of NK cells and increases in serum concentrations of the cytokines interferon-alpha and TNF-alpha, but these changes did not persist. No other immune system responses were detected. Because this was an uncontrolled study, it is unclear whether any of the observed clinical and/or immune system responses can be attributed to treatment with NDV oncolysates. Furthermore, because the lytic strain Italien was used in the study, the possibility that the observed tumor regressions were due, in part, to oncolysis cannot be ruled out.