First, let me say that there are two different issues that you (and Dr Chodak - who is not an RO) are conflating. The two questions are:
(1) Is brachy boost therapy better than EBRT alone for high risk patients
(2) Is brachy boost therapy better than surgery ± adjuvant RT for high risk patients.
There are two aspects to the word "better" - oncological control and toxicity.
(1) The first question is easy. That has Level 1 (meaning 4 large scale prospective randomized clinical trials) high grade evidence (the studies were well done) to support that oncological control is significantly better with a brachy boost. And it's not just a little better - it's a LOT better. In the ASCENDE-RT study (
at this link:
•The hazard ratio was 2.3 (i.e., those getting EBRT only were 2.3 times as likely to relapse compared to those getting the brachytherapy boost)
• Among those with high-risk prostate cancer, 9-year bPFS was
83% for the brachy boost cohort vs.
62% for EBRT-only.
• Among those with intermediate-risk prostate cancer, 9-year bPFS was 94% for the brachy boost cohort vs. 70% for EBRT-only.
• Among those who did not relapse, the median nadir PSA was 0.01 ng/ml (54% undetectable) for the brachy boost cohort vs. 0.25 for EBRT-only (8% undetectable).
These are not just "some improvement," as you state, those getting EBRT only were over twice as likely to suffer relapse after treatment.
As for toxicity, urinary toxicity was worse with the boost therapy:
• Late term Grade 3 GU toxicity reached 19% for the brachy-boost group vs. 5% for the EBRT-only group.
• Late term gastrointestinal (GI) toxicity was similarly mild for both groups.
So there is absolutely a trade-off. However, careful patient selection and use of IMRT rather than 3D-CRT (which was largely used in ASCENDE-RT) can greatly reduce that toxicity.
(2) The proof against surgery is less robust, and this is what Dr Chodak is addressing in the Kishan study. The Kishan study is a retrospective database review of over a thousand patients treated at several of the top cancer hospitals in America. It is discussed at this link:
/pcnrv.blogspot.com/2017/02/for-very-high-risk-patients-ebrt-bt-is.html. Now, just focusing on the surgery/brachy boost comparison, they found that:
• The 10-year rates of distant metastases were
39.9% for RP
19.7% for EBRT + BT
•The 10-year rates of prostate cancer-specific mortality (PCSM) were
20.3% for RP
14.1% for EBRT + BT
As anyone can readily see, those who received brachy boost rather than surgery did about
twice as well in terms of metastases, and the 10-year death rate was 43% higher with surgery. These are enormous differences.
Now, this is considered to be Level IIA evidence, which is not as reliable as the Level I evidence proving brachy boost is superior to EBRT alone. It should be noted that the problem with Level II evidence is selection bias - that the group that got therapy A is different from the group that got therapy B. In this case, the selection bias worked the other way -- it was
in favor of surgery. Surgery patients were about
10 years younger and had less advanced disease at the time of diagnosis. If it were a randomized study, we would expect the outcomes to favor brachy boost therapy even more.
While Dr Chodak (and as I also pointed out in my article) is right that Level 1 evidence is absolute proof, we will
never have a randomized trial of this in the US. We have to make the decision based on available evidence.