Salvage radiation therapy for PSA recurrence following radical prostatectomy

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Mar 23 2006

Salvage radiation therapy to the prostatic fossa is often employed in patients with rising PSA after radical prostatectomy (RP). Interestingly, only 25% of men with rising PSA after RP have a positive prostatic fossa biopsy, yet 70% of men with a negative biopsy will have their PSA decline to undetectable levels following salvage external beam radiotherapy.

In this study, Pazona and colleagues look at the results of external beam radiotherapy for PSA recurrence in a single surgeon series (William Catalona), examining both 10 year outcome estimates as well as factors that predict response.

Over a 20 year period, 3478 patients underwent RP for clinically localized prostate cancer by Dr. Catalona. Of these, 631 (18%) had evidence of cancer progression after surgery. Of these, 307 patients received local radiation therapy (median dose 63Gy) to the prostatic fossa. Of these, 223 patients had sufficient follow-up data available for analysis. The authors then examined clinical and pathological factors that predicted response to radiation therapy.

The median time from time from RP to PSA recurrence was 23 months (range 1-129). There were 162 (73%) responders to radiation therapy defined as PSA < 0.3 ng/ml after therapy. There was no difference noted with regards to clinical or pathological stage, age at surgery, margin status, or interval between RRP and radiation therapy between responders and non-responders. Gleason 8-10 was more common in non-responders (28% vs. 13%) and the median PSA at start of radiation was higher in non-responders (1.2 ng/ml vs. 0.7 ng/ml, p<0.01). There was a trend towards a shorter PSA doubling time (PSADT) in non-responders which was not significant (59% had PSADT < 10 months, vs. 39% with PSADT <10 months in responders, p=0.06). Non-responders were more likely to have a preoperative PSA > 20 ng/ml (67% vs. 47% in responders). The presence of seminal vesicle invasion or lymph node involvement significantly correlated with a worsened outcome following radiation (p=0.002).

The 5 and 10 year progression free survival for the entire cohort was 40% and 25%, respectively. The 5 and 10 year progression free survival for the patients who responded to radiation therapy was 55% and 35%, respectively. Men with a PSA < 1.3 ng/ml at the start of radiation therapy had a significantly better outcome (p=0.027). In multivariate analysis, only the presence of seminal vesicle invasion was associated with progression free survival after radiation therapy for PSA recurrence (p=0.003)

This study demonstrates that while initial response to radiation therapy to the prostatic fossa with PSA recurrence after RRP is good (73%), a durable response out to 10 years from salvage radiation is only maintained in 25%. Patients who do have an initial response to radiation therapy have the best outcome, with 35% progression free at 10 years. Further maturation of this data will determine the affect of salvage radiation therapy on patient cancer specific survival.

By Christoper G. Wood, MD

Reference:

J Urol 174:1282-1286, October, 2005.