It has been accepted that Zoledronic acid (ZA)(Zometa) reduces the onset risk of skeletal-related events (SRE) caused by bone metastasis in prostate cancer as well as improving their quality of life (QOL). ZA has become a standard supportive therapy for men with prostate cancer who have bone metastasis.

However, there is an issue which I have written about before as when is the best time to start ZA treatment. In a study presented at the recent ASCO GU Conference the researchers investigated whether combination of ZA could delay PSA relapse of prostate cancer and prevent the development of SREs.

Men were randomly classified in two groups, one receiving combined androgen blockade (CAB) alone and another receiving CAB + ZA treatment.

In the CAB + ZA group, 4 mg ZA was intravenously administered every 4 weeks with the start of treatment. The first end point was a period to PSA relapse, and the secondary end point was SREs rate.

Between 2006 and 2011 thirty one men were treated with CAB alone and 29 were treated with CAB + ZA. There were no significant differences in the baseline characteristics in the both groups, and the mean observation period was 27.4 months and 32.1 months, respectively.

They found that there was no significant difference in progression free survival (PFS) (p=0.073), however, there was a tendency that CAB + ZA showed a better PFS than CAB alone. In a sub analysis using the men with more than Gleason score 7, CAB +ZA group showed significantly longer PFS than the CAB group (p=0.021).

A statistically significant difference was seen in the SRE rate between the two groups (p=0.019) with the ZA tending to delay the occurrence of SRE in prostate cancer patients.

The researchers concluded that the use of ZA at the beginning of hormonal therapy has a preventive effect on the occurrence of SREs as well as a relapse-delaying effect, especially in the men with high Gleason scores and severe bone metastasis.

Men receiving long term ZA treatment must be carefully observed by their doctors since the long-term use of ZA may increase the incidence of adverse effects. They concluded that CAB-ZA treatment may be recommended for the treatment of prostate cancer patients with bone metastasis.

J Clin Oncol 32, 2014 (suppl 4; abstr 207)
Author(s): Satoru Ueno, Atsushi Mizokami, Takashi Fukagai, Naohiro Fujimoto, Hitoshi Ohoka, Yukihiro Kondo, Gaku Arai, Hisamitsu Ide, Mikio Namiki; Kanazawa University Graduate School of Medical Science, Kanazawa, Japan; Showa University School of Medicine, Tokyo, Japan; University of Occupational and Environmental Health, Kitakyusyu, Japan; National Hospital Organization, Kobe Medical Center, Kobe, Japan; Department of Urology, Nippon Medical School, Tokyo, Japan; Dokkyo Medical University Koshigaya Hospital, Saitama, Japan; Teikyo University Hospital, Tokyo, Japan

Joel T Nowak, M.A., M.S.W.