Early data from a German report seems to suggest that the clinical effects of cabazitaxel and abiraterone acetate in routine clinical practice are similar to those observed in Phase III clinical trials.
There is always a concern that when new drugs start to be used in routine clinical practice — as opposed to under the strict controls of clinical trials — there may be new side effects observed or less good outcomes among patients. This is especially the case in drugs approved for later stages of disease, e.g., metastatic, castration-resistant prostate cancer (mCRPC).
Abiraterone acetate and cabazitaxel have both been approved for the treatment of patients with mCRPC who have progressive disease after at least one cycle of docetaxel-based chemotherapy. Heck et al. have now published data from their early experience of using these drugs for their approved indications (under compassionate use initiatives supported by the manufacturers of these two drugs or under normal “on label” use guidelines). All patients were treated at a single institution.
Here is a summary of their findings:
- 15 men were treated with cabazitaxel and 39 with abiraterone acetate.
- Among the patients treated with cabazitaxel
- 7/15 men (46 percent) had PSA reductions of > 50 percent within 3 months.
- 2/15 men (15 percent) had PSA progression.
- Disease was controlled in 83 percent of the patients.
- Grade 3/4 neutropenia was documented in 40 percent of patients.
- Grade 3/4 anemia was documented in 20 percent of patients.
- Febrile neutropenia was observed in 2/15 patients (13 percent).
- Grade 3/4 non-hematologic toxicities included diarrhea (2/15 patients, 13 percent) and polyneuropathy (2/15 patients, 13 percent).
- Among the patients treated with abiraterone acetate
- 14/39 men (35 percent) had PSA reductions of > 50 percent within 3 3 months.
- 18/39 men (46 percent) had PSA progression.
- Disease was controlled rate in 47 percent of patients.
- Grade 3/4 anemia was documented in 5 percent of patients.
- Grade 3/4 thrombocytopenia was documented in 5 percent of patients.
- Grade 3/4 non-hematologic toxicities included fatigue (8/39 patients, 20 percent), sweating (7/39 patients, 18 percent), and constipation (4/39 patients, 10 percent).
The authors conclude that routine clinical use of cabazitaxel and abiraterone acetate is associated with response rates “comparable” to the response rates observed in Phase III clinical trials and with “acceptable” side effects.