CT + ADT vs. 3D-CRT + ADT for first-line treatment of “high-risk” prostate cancer

A South Korean research team has just published data from a small, prospective, case-matched study comparing outcomes after cryotherapy + androgen deprivation therapy (CT + ADT) to outcomes after three-dimensional conformal radiation therapy + androgen deprivation (3D-CRT + ADT) in patients with high-risk prostate cancer.

Ko et al. enrolled 33 patients with high-risk prostate cancer into this prospective study. These 33 patients were all treated with CT + ADT. The ADT was started 3 months prior to cryotherapy and continued for 24 months post-CT.  The outcomes of these patients were then compared with outcomes of 33 other carefully matched patients who had received 3D-CRT with the same protocol for ADT. Biochemical recurrence was assessed on the basis of three different criteria: the American Society for Therapeutic Radiation Oncology (ASTRO) criteria, the Phoenix criteria, and a simple PSA cutoff value of 0.5 ng/ml.

The results of this study are reported as follows:

  • Median follow-up was 61.0 ± 11.9 months for the CT + ADT group and 86.0 ± 15.8 months for the 3D-CRT + ADT group.
  • Biochemical recurrence in the CT + ADT group as compared to the 3D-CRT +ADT group was:
    • 57.0 vs.  54.5 percent based on the ASTRO criteria
    • 21.2 vs 21.2 percent based on the Phoenix criteria
    • 54.5 vs. 54.5 percent based on the PSA cutoff of 0.5 ng/ml.
  • Biochemical recurrence-free survival times in the CT + ADT group compared to the 3D-CRT + ADT group were:
    • 54 ± 10 vs. 68 ± 12 months based on the ASTRO criteria
    • 65 ± 5 vs. 93 ± 19 months based on the Phoenix criteria
    • 51 ± 4 vs. 70 ± 18 months based on the PSA cutoff or 0.5 ng/ml.
  • The differences between the biochemical recurrence-free survival times for each group itemized above were not statistically significant.
  • No major complications (including rectourethral fistula and incontinence) were noted among the patients treated with CT + ADT.

Ko et al. conclude, based on this pilot study, that first-line CT + ADT offers a comparable outcome to 3D-CRT + ADT in high-risk prostate cancer.

Unfortunately (based on the data in the abstract, because we do not have access to the entire published paper), The “New” Prostate Cancer InfoLink feels we need some additional information before we can draw such a conclusion.

In the first place, there is no clear definition of “high-risk” prostate cancer. Are these patients high risk according to the D’Amico criteria or on the basis of some other categorization? Second, even if the differences between the biochemical recurrence-free survival times are not statistically significant, there certainly seems to be a trend toward longer biochemical recurrence-free survival among the patients treated with 3D-CRT + ADT. And third, we don’t know what the dose of 3D-CRT was or whether it was directed exclusively to the prostate or also to the surrounding tissues. 3D-CRT is no longer the standard of care for radiation therapy in the US today. In the US, these patients would be getting targeted IMRT or IGRT, potentially with at least some wide-field radiation (depending on how “high risk” prostate cancer had been defined).

Data from this trial need to be considered in light of the results of the Calgary trial first reported in 2009 by Donnelly et al., which showed that cryotherapy was non-inferior to external beam radiation therapy as a first-line treatment for localized prostate cancer. Quality of life data from that trial were later reported by Robinson et al.

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