Clinical trials require endpoints. Endpoints are predetermined events that signal an individual subject’s goal for completing the trial. The FDA is interested in survival, it is the most important clinical trial endpoint, but to measure survival we must have deaths.
On one hand we are fortunate that prostate cancer does often progress slowly, the normal course of the disease can end in death, but it can take many years to have enough men in a trial to die to be able to having meaningful statistics comparing the numbers of deaths (or the survival rate) for one group, the investigational group, against the control group (the group just receiving the standard of care along with a placebo).
We are in a constant hunt for good endpoints, often referred to as biomarkers that can reliably predict death without having to actually wait for death.
At the recent ASCO meeting there were two studies presented that have the potential to establish new, earlier endpoints, which would stand in for death, for clinical trial outcomes.
Abstract 5006 described a computational method of quantifying bone scan results called the "automated bone scan index." Automated bone scan index values were found to be associated directly with overall survival, radiographic progression-free survival, and skeletal events to a higher degree than our usual clinical measures. The next step will be to evaluate if this endpoint would remain valid after treatment and then continue correlate with outcomes.
In another abstract, Abstract 5007 circulating tumor cells (CTCs) were found to correlate with survival outcomes.
The best correlates with overall survival were seen in CTC conversion from a level of > 5 to < 5 and going from CTCs being present to a "CTC 0" state. This method is made difficult because as many as 50% of the men in a clinical trial will not have the requisite numbers of CTCs, or may indeed not have any CTCs at all.
Things are looking up. The continued development and validation of alternative endpoints is vital. Developing them will save research dollars and allow good drugs to reach the market, and extend our life more quickly than our waiting for men to die.
Joel T. Nowak, MA, MSW wrote this Post. Joel is the CEO/Executive Director of Cancer ABCs. He is a Cancer Thriver diagnosed with 5 primary cancers - Thyroid, Metastatic Prostate, Renal, Melanoma and a rare cancer, Appendiceal Cancer.
