Baseline data from the control arm of the STAMPEDE trial

One of the more interesting sets of data on metastatic prostate cancer to be presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago this year will be some of the very earliest data from the STAMPEDE trial, which we have discussed in some detail in an earlier post.

Between October 2005 and December 2012, the investigators enrolled 3,703 men into STAMPEDE, making it the largest-ever, randomized, controlled trial in the treatment of prostate cancer. Enrollees into this trial must have

  • Either evident metastatic prostate cancer (TxNxM1 disease)
  • Or high-risk, locally advanced prostate cancer (e.g., TxN1M0 disease)
  • And they must be starting androgen deprivation therapy (ADT) for the first time

In the data to be presented at the ASCO meeting, Clarke et al. will offer survival data for newly diagnosed men with M1 disease in the control arm of the study — i.e., men who were treated exclusively with ADT and then, later, when castration-resistant, with docetaxel-based chemotherapy and other newer forms of therapy.

The data from these patients will be the basis for comparison — in the future — for the potential benefits of other forms of add-on therapy at the time of initial treatment.

Patients were eligible for inclusion in this analysis if they were

  • Newly diagnosed with M1 disease
  • Randomized to the trial’s control arm (i.e., ADT alone for at least 2 years)
  • Diagnosed no more than 6 months prior to randomization

Here are the core data to be reported in more detail by Clarke et al. at the ASCO meeting:

  • The total study cohort comprised 630 eligible patients with newly-diagnosed M1 disease.
    • 393/630 patients (62 percent) had metastasis to bone alone.
    • 78/630 patients (13 percent) had metastasis to soft tissues alone.
    • 159/630 patients (25 percent) had metastasis to bone and to soft tissues.
    • Metastases to soft tissues were predominantly to the lymph nodes.
  • The average (median) age of patients at randomization was 66 years.
  • The median PSA level of the patients at randomization was 105 ng/ml
  • The median time from diagnosis to randomization was 69 days (max. 180 days).
  • The median duration of ADT prior to randomization was 46 days (max. 105 days).
  • 129/630 patients (20 percent) had died at the time of the current analysis.
  • 111/630 patients (18 percent) had died of prostate cancer.
  • Median overall survival (OS) from randomization is 42 months.
  • Two-year OS  = 74 percent in this cohort and
    • Among the men with bone-only metastasis, the 2-year OS = 77 percent.
    • Among the men with soft tissue-only metastasis, the 2-year OS = 85 percent.
    • Among the men with bone and soft tissue metastasis, the 2-year OS = 57 percent.
  • Median failure-free survival (FFS), as defined by a rising PSA, is 12 months.
  • Two-year FFS = 22 months in this cohort.

Clarke et al. conclude that:

Survival, and particularly FFS, remains relatively poor for men presenting with M1 disease starting long-term [ADT], despite potential access when castration-resistant (CRPC) to docetaxel and other newer therapies.

The median overall survival of 42 months for patients newly diagnosed with metastatic disease is an improvement over what we used to see 20 years ago (when it used to be estimated that men so diagnosed had a life expectancy of about 36 months). However, as Clarke et al. note, “Better first line therapy [for men diagnosed with M1 disease] is required.” Future data to be reported from the STAMPEDE trial will be compared to the baseline data reported here. Hopefully it will help us to establish a significantly better standard of first-line care for men initially diagnosed with M1 prostate cancer.

However, based on the current data, as Clarke and his colleagues note, men with M1 disease will spend most of their remaining life with CRPC as opposed to hormone-sensitive disease, and this has important implications for the patients, for their clinicians, and for the conduct of future clinical trials.

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