By Edward Li, PharmD, BCOP, Drugs and Biologics Editor
There have been relatively few advances in recent years for the treatment of castration-recurrent (i.e., hormone refractory) metastatic prostate cancer. In the 1990s, systemic therapy for this particular setting was palliative in nature, utilizing chemotherapy with mitoxantrone plus prednisone . Then, around 2004, docetaxel-containing regimens were shown to increase survival and quality of life when compared to mitoxantrone/prednisone . Based on this information, docetaxel-containing regimens gained popularity for treating patients who developed castration-recurrent metastatic prostate cancer.
Recently, the FDA approved a novel treatment, sipuleucel-T, for the treatment of asymptomatic or minimally symptomatic castration-recurrent metastatic prostate cancer. Sipuleucel-T is a cancer vaccine that utilizes the patient’s peripheral blood mononuclear cells and antigen presenting cells (APC), which are collected via leukapheresis and primed to target prostatic acid phosphatase (PAP), which is found in most prostate cancer cells. The subsequent infusion of the autologous cells causes an immune response towards prostate cancer cells. Recent clinical trials showed that sipuleucel-T increased median survival by approximately four months when compared to placebo in patients with asymptomatic or minimally symptomatic castration-recurrent metastatic prostate cancer . However, time to progression was not statistically significant in one clinical trial.
A recent NCCN Trends™ Survey asked health care practitioners how likely they are to utilize sipuleucel-T when treating asymptomatic or minimally symptomatic patients with prostate cancer. The survey was conducted in May 2010 with 931 respondents, the majority of whom identified themselves as practicing physicians specializing in oncology (74%), followed by advanced practitioners or nurses (11%), and oncology pharmacists (6%). The remainder consisted of other types of clinicians or clinicians not currently in practice.
Survey participants were asked to consider various clinical scenarios: metastatic castration-recurrent disease, post-chemotherapy; metastatic castration-recurrent disease, chemotherapy-naïve; PSA rising, castration-recurrent, no other evidence of metastases; metastatic disease, before androgen deprivation therapy; and early stage disease as primary therapy. Unsurprisingly, respondents reported that they were most likely to include therapy with sipuleucel-T for clinical situations that fell within the scope of the FDA-approved label. The percentage of respondents stating they were “very likely” or “likely” to use sipuleucel-T in patients with metastatic, castration-recurrent disease, post-chemotherapy or chemotherapy-naïve was 56% and 40%, respectively. For clinical situations that did not reflect the FDA-approved label (PSA rising, castration-recurrent, no other evidence of metastases; metastatic disease, before androgen deprivation therapy; and early stage disease as primary therapy), respondents were less likely to utilize the therapy. The percentage of respondents stating they were “very unlikely” or “unlikely” to use sipuleucel-T was 71%, 85%, and 87%, respectively.
Additionally, the survey asked participants their opinion about the price for a complete course of sipuleucel-T. About half of the respondents answered that a reasonable sales price would be less than $25,000 for the complete course of sipuleucel-T. In actuality, a complete course of the therapy is expected to be about $90,000 .
The NCCN Clinical Practice Guidelines (NCCN Guidelines™) for Prostate Cancer recently added sipuleucel-T to the list of treatment options for patients with metastatic, castration-recurrent prostate cancer as a Category 1 indication. According to the NCCN Guidelines™, “Sipuleucel-T is appropriate for asymptomatic or minimally symptomatic patients with ECOG performance status 0-1. It is not recommended for patients with visceral disease and a life expectancy less than six months.”
The treatment landscape for metastatic prostate cancer is expanding. In addition to sipuleucel-T, cabazitaxel (in combination with prednisone) was recently approved by the FDA to treat patients with castration-recurrent metastatic prostate cancer who have previously been treated with a docetaxel-containing regimen. After years devoid of novel therapies, patients living with prostate cancer now have additional options when faced with castration-recurrent, metastatic disease.
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