Detection of local prostate cancer recurrence after EBRT

Data from a small study at the University of California at San Francisco suggest that magnetic resonance (MR) spectroscopic imaging is better than  T2-weighted MR imaging alone for the detection of locally recurrent prostate cancer after definitive external beam radiation therapy (EBRT) as first-line therapy.

Westphalen et al. carried out a retrospective analysis of data from 64 patients who received endorectal MR imaging, MR spectroscopic imaging, and transrectal ultrasonographically guided biopsy for suspected local recurrence of prostate cancer after definitive EBRT. (The abstract of this paper does not state the precise reason for suspicion of recurrence, but we should probably assume that the patients had a rising PSA that exceeded either the ASTRO or the Phoenix criteria for disease progression.) About half of the patients (33/64) had also received adjuvant androgen deprivation therapy (ADT) .

The analysis showed that:

  • Recurrent prostate cancer was identifiable on biopsy in 37/64 patients (58 percent).
  • The recurrence was evident in just lobe lobe of the prostate in 28 patients but was evident in both lobes in 9 patients (total of 46 affected prostate sides).
  • Use of combined T2-weighted MR imaging and MR spectroscopic imaging, as compared with T2-weighted MR imaging alone, significantly improved the ability to detect local recurrence (P = 0.001).

The authors conclude that addition of MR spectroscopic imaging to T2-weighted MR imaging “significantly improves the diagnostic accuracy of endorectal MR imaging” in the detection of locally recurrent prostate cancer after definitive EBRT.

Now it has to be said that although there was a statistically significant improvement, the relative improvement was not huge. In other words, it may not be enough to offer a compelling reason to give every patient with recurrence after first-line EBRT a comination of MR spectroscopic with T2-weighted MR imaging. It also doesn’t give us much help with knowing how best to treat these patients. Salvage surgery for such patients is a difficult operation with a relatively high risk for side effects; HIFU and cryotherapy may be appropriate options. In some patients it may also be possible to use brachtherapy (depending on the total dose of radiation already received). However, for many such patients the only real option is hormone therapy — and then the question becomes “when?” to initiate the hormone therapy.

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