The ASCENDE-RT randomized clinical trial demonstrated that the combination of external beam radiation therapy with a brachytherapy boost (EBRT + BT) significantly reduced biochemical progression-free survival. A new data analysis suggests that this benefit may extend to prostate cancer survival as well.
>Xiang and Nguyen searched the SEER database to identify 52,535 high- and intermediate-risk patients who were treated with EBRT + BT or EBRT alone between 2004 and 2011. Of that total, 20 percent received EBRT + BT, and one-third were high risk. They matched patients for risk factors, and adjusted for other variables that affect survival.
By 8 years after treatment, the adjusted prostate cancer-specific mortality (PCSM) rates were:
- 8 percent for EBRT + BT
- 7 percent for EBRT alone
- 4 percent for EBRT + BT among high-risk patients
- 6 percent for EBRT alone among high-risk patients
- Mortality was not significantly reduced among intermediate-risk patients
The authors conclude:
BT boost was associated with a moderate reduction to PCSM in men with localized unfavorable-risk prostate cancer. Those most likely to benefit are younger patients with high-risk disease.
Of course, this was a database analysis and not a randomized clinical trial, so the findings are provisional until better data are available. The mortality numbers are also small, reflecting the long natural history of prostate cancer progression even among high-risk patients, and the fact that, at modern dose levels, both the monotherapy and the combined modality may cure or delay progression for a long time.
As we’ve seen, the combined modality approach does increase the side effects of treatment. The fact that there is so far no discernable survival benefit for intermediate-risk patients should dissuade those with “favorable” intermediate risk prostate cancer from pursuing boost therapy. Each “unfavorable” intermediate-risk and high-risk patient will have to assess for himself whether the added toxicity is worthwhile.
Editorial note: This commentary was written for The “New” Prostate Cancer InfoLink by Allen Edel.