Waiting to start salvage radiation therapy safe, according to study

September 20, 2013

Outcomes following salvage radiation therapy after recurrent prostate cancer in a racially mixed cohort are no better when it’s started at a PSA level

Durham, NC-Outcomes following salvage radiation therapy after recurrent prostate cancer in a racially mixed cohort are no better when it’s started at a PSA level <0.5 ng/mL compared with a level <1.0 ng/mL.

The data suggest that waiting a short time to start salvage radiation, as long as the PSA level is <1.0 ng/mL, does not lead to worse outcomes compared with starting “super early,” said lead investigator Stephen J. Freedland, MD, who presented the data at the AUA annual meeting in San Diego.

The AUA recommends that a PSA level of 0.2 ng/mL be used to determine recurrence of prostate cancer. Other groups use a PSA value of 0.4 ng/mL.

“The implication is that once you recur, you should undergo radiation. Our data seem to indicate that it’s OK to wait a little bit, follow the PSA, determine the PSA doubling time, and better assess whether the patient needs radiation or not,” said Dr. Freedland, associate professor of surgery and associate professor in pathology at Duke University, Durham, NC, and staff physician at the Durham VA Medical Center.

Studies have demonstrated that a PSA doubling time <9 months is associated with a higher risk of prostate cancer death, he said.

The Shared Equal Access Regional Cancer Hospital (SEARCH) database was used to identify men with recurrent prostate cancer who started salvage radiation at least 6 months after radical prostatectomy and received no concurrent hormonal therapy. The PSA level prior to salvage radiation was analyzed in four groups: 0.2 to 0.5 ng/mL, 0.51 to 1.0 ng/mL, 1.01 to 1.5 ng/mL, and >1.5 ng/mL. Radiation failure was defined as PSA >0.2 ng/mL above the post-salvage radiation nadir.

Log-rank test and Cox models adjusted by the pre-radical prostatectomy PSA level, Gleason score, margin status, seminal vesicle invasion, and race were used to test whether pre-salvage radiation PSA was associated with salvage radiation therapy failure.

Of 286 men, 145 (50.7%) were Caucasian, 130 (45.5%) were African-American, and 11 (3.8%) were from other races.

PSA <1.0 ng/mL key to success

With a median follow-up of 49 months, 76 men (26.6%) had salvage radiation failure. In univariate analysis, the PSA level prior to salvage radiation was associated with salvage radiation failure (p<.0001). Men with PSA <1.0 ng/mL had less failure than others. Race was not related to failure.

In adjusted analysis, the risk of salvage radiation failure was similar between PSA groups of 0.2 to 0.5 ng/mL and 0.51 to 1.0 ng/mL (p=.82), but increased by more than twofold for groups with PSA levels of 1.01 to 1.5 ng/mL (hazard ratio [HR]: 2.5; p=.019) and >1.5 ng/mL (HR: 2.6; p=.006) versus the group with the lowest PSA levels.

“As long as you’re below 1.0 ng/mL, super early was not better than just early. Many men might be able to be spared radiation. Even for the patients who need it, by waiting a short amount of time, our data suggest that you haven’t harmed them,” Dr. Freedland said.

“It’s a modest-sized study that needs validation. It’s consistent with what other people have shown, although they didn’t highlight that aspect of their study.”UT

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