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Metronomic-dose IL-2 combined with radiation, PSA vaccine, stimulated immunologic response
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The results of a recent study showed that a metronomic dose of interleukin-2, when combined with radiation and PSA vaccine, produced similar results to low-dose interleukin-2 with fewer toxicities.
Researchers at the NCI and the FDA enrolled 18 men with localized prostate cancer into a single-arm trial.
The men were assigned to vaccination once every four weeks, with granulocyte-macrophage colony–stimulating factor given on days one to four, and 0.6 mIU/m2 of IL-2 assigned on days eight to 21 after each vaccination. The men were assigned to definitive external beam radiation therapy after the third vaccination cycle. Researchers compared toxicity and immunologic activity with a previously reported regimen that contained a higher dose of IL-2.
The researchers said 17 patients received all eight planned cycles of the vaccine and IL-2. Five of eight patients who were HLA-A2+ evidenced at least a threefold increase in PSA-specific T cells.
The researchers found toxicities were “generally mild;” only seven of 140 cycles led to grade-3 toxicities. – by Jason Harris
Clin Cancer Res. 2008;14:5284-5291.
The researchers reported the results of a carefully conducted trial that indicated that specific immune response against prostate antigens may be induced in men receiving definitive external beam irradiation by combining irradiation, low-dose IL-2 and PSA–based vaccine. The regimen was safe and well tolerated. This is an important first step in evaluating this approach. It is critical to consider the endgame to the approach immediately. A substantial phase-2, or preferably a randomized phase-3 trial, is needed for this approach, perhaps as the next step. Demonstrating apparent safety and immune response is a good start, but there are many steps to go. Consideration of trial design combining new approaches with definitive, curative therapy is a challenging endeavor. In small numbers of patients, agents which are believed to be helpful may abrogate or reduce curative outcome, and such abrogation will be very hard to detect. That is why it is critical to analyze robust, clinically important outcome measures as quickly as possible in these types of trials.
– Donald L. Trump, MD, FACP
HemOnc Today Editorial Board member