It was announced today that preliminary results from the Phase II STAND trial demonstrates continued and what is described as a robust immune response with Provenge (sipuleucel-T) that continues two years after completing treatment in men with biochemically-recurrent prostate cancer (BRPC). This finding, along with data from the ongoing Phase IV registry PROCEED trial, are being presented at the 2015 Genitourinary Cancers Symposium (ASCO GU) conference.
The STAND study is a randomized, Phase II trial that consisted of two patient study groups designed to eventually allow the possible expansion of the FDA approval for Provenge to men who are still hormone responsive. One study group completed Provenge two weeks before initiation of androgen deprivation therapy (ADT) and the second received Provenge three months after the start of ADT.
As mentioned earlier, Provenge is not currently approved for men with BRPC until they become castrate resistant. This trial looked at this unapproved cohort of men and found that an immune responses was observed in both study arms. It also suggests there may be a greater cellular immune response in patients who received Provenge prior to ADT compared with those who received it following three months of ADT.
This brings me to two comments about Provenge and this data.
1- The measurement of an immune response in these trials is by way of a surrogate marker, one that is generally accepted, but not validated as a marker for prostate cancer survival. This means there is always the potential that the immune response being measured is not predictable of a longer survival time for men with prostate cancer.
2- Given that the immune response seems stronger in ADT naive men we need to wonder if Provenge were given earlier, while men were still either still hormone responsive or even prior to starting ADT, would the actual survival advantage provided by Provenge have been even longer than shown by the trial used to secure FDA approval?
On the negative Provenge was just rejected by National Institute for Health Care Excellence (NICE) which is the equivalent to the United State’s FDA for the UK and Whales.
The question now is will Provenge be around long enough for these questions to be answered? Dendreon’s bankruptcy and now the NICE rejection seem to be building one hurdle after another for the potential of the long term survival of Provenge.
Joel T. Nowak, M.A., M.S.W.