IMRT probably no better than 3D-CRT after radical prostatectomy

In another relatively unsurprising finding, a paper in JAMA Internal Medicine has suggested that– from a clinical point of view — there is little difference in the outcomes of men treated with older rather than newer forms of radiation therapy after first-line surgery for localized prostate cancer.

There are three basic reasons why a man may have radiation therapy after he has already received first-line radical surgery for localized prostate cancer:

  • His PSA doesn’t drop down to an undetectable level (i.e., < 0.1 ng/ml) within 3-6 months after surgery, suggesting the need for immediate additional treatment.
  • His PSA does drop to an undetectable level after surgery, but then either it starts to rise again much too quickly or it is rising more slowly but exceeds the standard level defining biochemical failure (0.2 ng/ml), and the patient needs “salvage” radiation.
  • Pathological features identified at the time of surgery suggest that “immediate” adjuvant radiation therapy would be wise.

In all such cases, the patient’s prostate has already been removed, and so radiation therapy will be administered to the prostate bed and to some amount of surrounding pelvic tissue. (The precise area to be radiated may depend on whether any good data are available to suggest where cancer may still be found.)

What this means is that the benefits of new “high-tech” forms of highly targeted radiation therapy, which are highly applicable to the use of radiation as a first-line treatment, become much less important because one has to radiate a wider area of some type beyond the prostate.

Goldin et al. set out to use data from the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database to compare outcomes associated with the use of intensity-modulated radiation therapy (IMRT) to outcomes from the use of the older conformal type of radiation therapy (3D-CRT) in the post-prostatectomy setting, and to look very specifically at disease control and morbidity outcomes of these two different types of treatment.

Specifically, the authors identified and compared data from just over 1,000 patients, all of whom received second-line radiation therapy within 3 years of a first-line radical prostatectomy between 2002 and 2007 and whose claims data could be followed through 2009.

Here are the key study findings:

  • 457/1,014 patients (45 percent) were treated with IMRT.
  • 557/1,014 patients (55 percent) were treated with 3D-CRT.
  • Use of IMRT increased from 0 percent of cases in 2000 to 82.1 percent in 2009.
  • Men treated with IMRT as opposed to 3D-CRT exhibited no significant differences in rates of
    • Long-term gastrointestinal morbidity (adjusted incidence rate ratio [RR] = 0.95)
    • Urinary non-incontinent morbidity (RR = 0.93)
    • Urinary incontinence (RR = 0.98)
    • Erectile dysfunction (RR = 0.85)
  • Men treated with IMRT as opposed to 3D-CRT also exhibited no significant difference in subsequent treatment for recurrent disease (RR = 1.31).

In other words, there was minimal evidence of any real improvement in the rates of morbidity or cancer control when patients were given IMRT as opposed to 3D-CRT as second-line radiation therapy. To quote the authors, “The potential clinical benefit of IMRT in this setting is unclear.”

On the other hand, of course, the cost of using IMRT as opposed to the older 3D-CRT in this setting is very definitely significant.

The “New” Prostate Cancer InfoLink would emphasize that this study does have limitations, and it is quite certainly the case that:

  • Some patients probably do benefit from the use of IMRT as opposed to 3D-CRT as second-line radiation therapy after radical prostatectomy (especially in those cases when the area to be radiated is small and highly targetable).
  • The facility cost of having 3D-CRT and IMRT equipment available for daily use at any radiation therapy center is considerable (especially if 3D-CRT is being used relatively rarely). Few facilities could afford to maintain both types of equipment for long.
  • This type of cost-effectiveness study based on retrospective analysis of Medicare billing data is always fraught with problems because of what the researchers don’t know.

Having said that, this study does raise the very valid question (yet again) of how we are going to manage the rapidly exploding costs of health care delivery if we insist on always using “over-qualified” technology to do things that older systems (with lowers costs) did equally well!

2 Responses

  1. I’ve been told I need adjuvant radiation after a positive margin measuring 4 mm (Gleason 7) was found in pathology after open RP for gleason 9 cancer in 2/6 biopsy samples preop. Seminal vesicles were involved but all 10 lymph nodes dissected were clear.

    What Gy level is indicated, how many sessions, and can radiation be limited to just the prostate bed since lymph nodes were not involved?

  2. Dear Robert:

    Those are questions you really need to ask your radiation oncologist because the answers all depend on precisely what type of equipment s/he intends to use and other factors that we don’t have information about.

    In theory, I can’t see why the radiation shouldn’t be limited to the prostate bed, but the number of sessions would depend on where in the prostate bed the positive margin is thought to have occurred and other factors.

    It also should be noted that if you originally had Gleason 9 disease (and this was confirmed by the post-surgical pathology), then you started out with a highly aggressiove form of prostate cancer. As a consequence, it may well be wise to see the radiation therapy as a necessary part of your overall treatment (to include the pelvis and the lymph nodes even though there was no sign of positive lymph nodes at the time of surgery). What you do not want to do is to have radiation limioted to the prostate bed only to see your PSA rising again 6 months later if itr can be avoided.

    And that reminds me … How low did your PSA go after surgery? That is another key factor tyhat is relevant to all of this.

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