Sipuleucel-T for metastatic castrate-resistant prostate cancer (mCRPC) offers a novel immunotherapy treatment option for a subset of patients, but the drug could be helping far more men than actually receive it, according to a speaker at the 37th Annual Congress of the Oncology Nursing Society.
Sipuleucel-T, which activates T cells to stimulate an immune response to prostate cancer, is a first-line treatment option for men with symptomatic or minimally symptomatic mCRPC. “It is the only category 1 recommendation by the National Comprehensive Cancer Network for this group,” said Allison Tyler, RN, BSN, OCN, CCRP, clinical research nurse at the Cleveland Clinic, Cleveland, Ohio.
In the pivotal IMPACT trial, men treated with the drug survived a median of 4 months longer than the control arm. Median overall survival was 25.8 versus 21.7 months, respectively, for a 22.5% reduction in risk (P=.032).1
Tyler noted that two-thirds of men treated with surgery or radiation are not cured of prostate cancer and will have a subsequent rise in the prostate-specific antigen (PSA) as an indicator of progression. Even after responding to androgen deprivation therapy, nearly all men will develop CRPC; 80% will then develop metastatic disease, almost half of them within 2 years.
“These patients often go undiagnosed,” she said. In an analysis of a population (N=2516) screened for possible inclusion in a recent clinical trial, 30% of men thought to have nonmetastatic CRPC were found to have metastatic disease on imaging.2
“It is commonly said, ‘We don’t have patients fitting the profile for sipuleucel-T,’ but we know the patient population is out there, and we are not finding them early enough,” Tyler suggested, emphasizing that the presence of advanced symptoms eliminates sipuleucel-T as a treatment option.
In a review of over 1167 patient charts at 70 oncology practices, 61% of men with mCRPC had no symptoms or only minimal symptoms at diagnosis of metastatic disease. There was no pain or pain controlled by nonnarcotic medication.3
Identifying the Population “Regular monitoring can help identify disease progression in CRPC while patients are still asymptomatic or minimally symptomatic, but there are no definite guidelines for doing so,” she said.
MRI effectively demonstrates extracapsular extension or seminal vesicle invasion. A CT scan is good for staging, however, early disease may be missed, and there is broad variation in sensitivity and specificity. Bone scans identify bone metastases, although negative results do not rule out disease. PET/CT scanning identifies tumors effectively and has high specificity for bone metastases.
Once patients are being treated with immunotherapy, they need to understand that they may not manifest a clear-cut “response” to the drug, which acts in a manner much different from that of chemotherapy. “The main goal of the clinical study was not to lower PSA levels, but to prolong survival, which was shown in the trial,” she said.
“The PSA may not plummet, as it did on earlier treatments, and patients may feel anxious about this,” she said. “They need to know that even if their PSA level does not decline, sipuleucel-T may help them live longer.”
Tyler acknowledged that the treatment, which is completed in 1 month, is expensive but maintained that it is covered by most health plans, and most patients have minimal out-of-pocket costs. “For the majority of patients, this drug is a reasonably priced treatment option,” she said.
References
- Kantoff PW, Higano CS, Shore ND, et al. Sipuleucel-T immunotherapy for castration-resistant prostate cancer. N Engl J Med. 2010;363:411-422.
- Yu EY, Nathan E, Higano CS. Detection of metastatic disease as a leading cause of screening failure in a phase III trial of zibotentan versus placebo in patients with nonmetastatic castration-resistant prostate cancer (CRPC). J Clin Oncol. 2011;29(suppl). Abstract 4655.
- Data on file. Dendreon Corporation.