The paraphrased RadOnc said...
that they still felt there was not enough of a history for them to advocate for it.
This raises a point I ponder a lot that has to do with decision making under conditions of uncertainty. I may have missed some studies, but the longest follow-up studies I have seen for each primary therapy treatment type are as follows:
HDR brachy monotherapy - 10 years (CET/Demanes)
HDR brachy+EBRT - 15 years (Kiel, Germany)
IMRT - 10 years (MSKCC)
LDR brachy monotherapy - 15 years (Seattle)
LDR brachy+EBRT - 25 years (RCOG)
Protons- 10 years (Loma Linda)
SBRT - 9 years (Katz)
Robotic RP - 10 years (Henry Ford Hospital, Detroit)
Laparoscopic RP - 10 years (Heilbronn, Germany)
open RP - 30 years (Johns Hopkins)
Active Surveillance - 20 years (Toronto)
Now, I was treated at the age of 57 and had an average life expectancy of 24 years, possibly more because I have no comorbidities. So unless I was willing to undergo
open prostatectomy, there was no data that could help me predict my likelihood of cause-specific survival and QOL out to the end of my reasonably expected days.
What's more, the therapies with the longest follow up (
open RP, brachy boost) also have the highest rates of serious SEs. With my low risk cancer, there seemed little need to take that risk with my quality of life.
While we may be tempted to wait for longer follow up, (1) we don't always have that luxury, and (2) there very likely will not
be any longer follow up. Not only is follow up expensive, there is also the problem of non-response, drop outs, and death from other causes. The 10-yr Demanes study, for example, started with 448 patients, but there were only 75 patients with 10 years of follow up. After the sample size gets this small, there is little statistical validity in tracking further changes.
An even bigger problem is what I call
irrelevance. Technological change and medical science learning continue at so brisk a pace that the treatment techniques 10 years from now are not likely to resemble anything currently available (another argument for active surveillance, if that's an option). Dose escalation, hypofractionation, IGRT technology, intra-operative planning, VMAT, variable multi-leaf collimators, cone-beam CT, and high precision linacs - all innovations that have mostly become available in the last 15 years have dramatically changed the outcomes of every kind of radiation therapy, and made them totally incomparable to the earlier versions. It's like comparing the new MacBook to the clamshell iBook I had in 2000. By the time we get the long term results, they are irrelevant to the decision now at hand.
I could also go off on a tangent about
surrogate endpoints.
So when do we have enough data to make a decision? That comfort level will vary among individuals. I was comfortable with 3-year data, and many brave souls (thank God for them!) are comfortable with clinical trials of innovative therapies. However, I will note that, in general, 5-year outcomes do not differ markedly from 10-year outcomes, both in biochemical recurrence-free survival and late-term toxicity. Most (but not all) recurrences - for both surgery and radiation - if they are going to occur, will occur within the first few years. Most late-term side effects of treatment - for both surgery and radiation - if they are going to occur, will have occurred within the first couple of years. So statistically, 5-year data affords a sound basis for making treatment decisions.