Friday, February 20, 2009

Adjuvant RT for prostate cancer (SWOG update Journal Club)

AC presents today on the recent SWOG adjuvant RT for prostate cancer update.

Approximately 1/3 of patients undergo prostatectomy for prostate cancer, and of those 1/3 have some form of biochemical recurrence.

There is some debate about the definitions of salvage vs adjuvant RT.  We define adjuvant RT as treatment postoperatively without a detectable PSA, however some institutions will include any treatment within six months of surgery as adjuvant.

30-60% of those undergoing RP have either ECE or Posititive margins.  Additional factors associated with failure include SVI, high GS, and pretreatment PSA.

Randomized Data
EORTC 22911 (Bolla, Lancet 2005) 1005 pts with pT3 or positive margins, randomized to 60Gy vs wait and see.  Results: improved cPFS, LRF, no difference in OS.  See prior post on this trial.  Approximately 2/3 of the wait and see group recieved salvage RT.  Additionally only 10% had detectable PSA.

ARO 96-02 (Wiegel, ASCO 2005) 385 with pT3N0 randomized to 60Gy vs wait and see.  In the randomization, all had an undetectable PSA. 20% had detectable PSA in this trial and were all treated with 66Gy.  in all groups biochemical control improved HR 0.79 p=0.08.  In the adjuvant group only, biochemical control improvement HR 0.49 p=0.001.  See also prior post for link.

SWOG 8794.  pT3 or positive margins, n=425.  Randomized to 60-64Gy vs observation.  Primary endpoint Metastasis Free Survival.  Accrual goal was 558.  Power 0.8, alpha 0.05, HR for MFS would be 0.66.  The accrual goal was revised when a lower event rate was seeing in the control group in 1996.  Longer follow up assumed, and accrual revised to 408.  Also revised to a two-sided test.

10% in intervention arm didn't receive treatment.  ~1/3 of patients in control arm recieved RT.  Also 1/3 had a detectable PSA.

Initial report in JAMA 2006 failed to meet MFS endpoint, though this was borderline p=0.07.  bRFS was improved.

Update with 12.6 years f/u.  DM free survival improved with RT (HR 0.71; 95% CI 0.54, 0.94; p = 0.016), and OS improved with RT (HR 0.72; 95% CI 0.55, 0.96; p = 0.023). NNT was 12 for DM free survival, and for OS NNT was 9.

No subgroup seemed to benefit more from RT.

Moinpour JCO 26:112, 2008: QOL data from this trial.  After year 2 bowel movement QOL was similar between RT vs obs.  In urinary QOL, RT had a consistent reduciton in QOL.  Global QOL seemed to be initially worse in the RT arm, but curves crossed at 2 years, and RT became superior at longer followup.

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