A new paper by Armstrong et al. has analyzed data from the original TAX327 clinical trial in an attempt to define specific patient “risk groups” based on the participants in that trial and how they responded to docetaxel-based chemotherapy.
To date, there have been no well-defined criteria than allowed us to predict how patients with metastatic, castration-resistant prostate cancer (mCRPC) might respond to chemotherapy.
In the TAX327 clinical trial, which was one of the two clinical trials that led to the original approval of docetaxel + prednisone as a treatment for men with mCRPC, 1,006 patients were randomized to receive docetaxel (on one or other of two schedules) or mitoxantrone, each in combination with prednisone. Of these 1,006 patients, 989 provided data on PSA decline within 3 months. Armstrong and his colleagues used these data to develop predictive factors for a 30 percent decrease in the patients’ PSA levels (30%PSAD).
Their study showed that four independent risk factors predicted a 30%PSAD: pain, visceral metastases, anaemia, and bone scan progression. Using this information, they divided patients into three risk groups, as follows:
A “good” risk group, which included patients having 0-1 of the four risk factors identified above, who had a median overall survival (OS) of 25.7 months, a 30%PSAD in 78 percent of the group members, and a measurable disease response in 19 percent
An “intermediate” risk group (2 factors), in which patients had a median OS of 18.7 months, a 30%PSAD in 66 percent of the group, and a measurable disease response in 9 percent
A “poor” risk group (3-4 factors), in which patients had a median OS of 12.8 months, a 30% PSAD in 58 percent of the group, and a measurable disease response in 5 percent
The validation cohort demonstrated a similar predictive ability for 30%PSAD, for tumor response, and for median OS.
The authors conclude that these risk groups “may facilitate evaluation of new systemic regimens warranting definitive testing in comparison with docetaxel and prednisone” and that “Prospective validation of this classification system is needed.”
The “New” Prostate Cancer InfoLink thinks that these risk groups may be helpful for physicians and their patients in coming to decisions about whether or not to go ahead with docetaxel-based chemotherapy, given the potential adverse effects of this therapy compared to the relatively limited patients in a significant proportion of all those treated. However, it would certainly be helpful to see prospective and independent validation of these risk groups if this is possible.