- More than half of men treated had long-term, durable disease control after salvage radiotherapy
- Pre-radiotherapy PSA velocity and PSA doubling time did not influence the interval to disease progression
- Disease progression was least likely when the pre-radiotherapy PSA level was £0.3 ng/mL
Multiple professional societies recommend salvage radiotherapy (SRT) as a curative treatment for men with prostate cancer who have isolated local recurrence or an increase in prostate-specific antigen (PSA) after radical prostatectomy. The optimal PSA level at which to initiate treatment is debated though, partly because most of the previous research was conducted before modern tests became available that can detect PSA <0.5 ng/mL.
By reviewing a cohort of patients who were treated in 2000 and beyond, researchers from the Department of Urology and Cancer Center at Massachusetts General Hospital have added to the data supporting early SRT—and the lower the PSA, the better, they say. Director of Research Adam S. Feldman, MD, MPH, Chief of Urologic Oncology, Douglas M. Dahl, MD, Urologist Francis J. McGovern, MD, and Director of the Genitourinary Service Jason A. Efstathiou, MD, DPhil, report their findings in Clinical Genitourinary Cancer.
The researchers examined the records of 307 patients at Mass General between 2000 and 2013 who underwent radical prostatectomy and postoperative SRT, without prior or concurrent androgen deprivation therapy. The median interval from surgery to the start of SRT was 2.7 years. At a median of 4.9 years after SRT completion, 134 patients' (44%) disease had progressed.
The primary endpoint of the study was interval to disease progression after SRT. Progression was defined as a PSA value ≥0.2 ng/mL greater than the post-SRT nadir, followed by a higher value; a continued increase in the serum PSA level despite SRT; initiation of systemic therapy after SRT completion; or the development of local recurrence, nodal failure or distant metastases.
The median interval to prostate cancer progression was 6.03 years, the researchers found. The likelihood of progression was lowest for patients who had a pre-SRT PSA level £0.3 ng/mL.
The risk of cancer progression increased as the pre-SRT PSA level increased. Patients undergoing late SRT (pre-SRT PSA >1.0 ng/mL) were 3.5 times more likely than those with values £0.3 ng/mL to experience treatment failure (P = .002).
Confirming previous research, the Mass General team found that a higher Gleason score, higher pathologic T stage and negative surgical margins were other predictors of disease progression.
Secondarily, the researchers investigated the effect of PSA velocity and PSA doubling time, which studies have identified as potential predictors of prostate cancer progression after SRT. However, pre-SRT values of PSA kinetics did not influence the rate of progression.
The researchers conclude that their findings may help guide decisions about the timing of SRT for recurrent prostate cancer after radical prostatectomy. They may also help identify patients who would benefit from escalated systemic treatment, such as androgen deprivation therapy.
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