More on the value of HDR brachytherapy added to EBRT


A few days ago we reported on a study which concluded that the addition of high-dose-rate (HDR) brachytherapy to intensity-modulated radiation therapy (IMRT) had limited short-term clinical benefit in the treatment of localized prostate cancer compared to IMRT alone. Newly published Australian data is arguably supportive of this viewpoint.

Zwahlen et al. have carried out a single-institution retrospective analysis of the  long-term outcomes after treatment for prostate cancer using dose escalation with HDR brachytherapy and 3-dimensional conformal external beam radiotherapy (3D-CRT), and compared them with outcomes for treatment of prostate cancer with 3D-CRT alone at the same institution.

At their institution, between 1998 and 2003, 587 patients were treated for clinically localized prostate cancer. Patients received either 3D-CRT (median, 46 Gy) with a single HDR brachytherapy implant delivering a fractionated dose of 18 Gy or 3D-CRT alone (median, 70 Gy). The study database could be broken down as follows:

  • 196 patients (33.4 percent) received combination radiotherapy.
  • 387 patients (65.9 percent) received 3D-CRT alone.
  • 246 patients (41.9 percent) were classified as intermediate risk.
  • 250 patients (42.6 percent) were classified as high risk.
  • 441 patients (75.1 percent) received neoadjuvant androgen deprivation therapy (ADT).
  • 116 patients (19.8 percent) received adjuvant ADT.

The authors defined biochemical failure using the American Society of Radiation Oncology (ASTRO) Phoenix definition (an increase in the PSA level to the nadir level + 2 ng/ml).

Study results are reported as follows:

  • The median patient follow-up was 5.5 years.
  • 5- and 7-year rates of biochemical progression-free survival were 82.5 and 80.3 percent, respectively, for the combined group and 81.3 and 71.0 percent, respectively, for 3D-CRT alone.
  • Overall survival rates at 5 and 7 years were 91.9 and 89.5 percent, respectively, for the combined group vs. 88.7 and 86.2 percent, respectively, for 3D-CRT alone.
  • Prostate cancer-specific survival rates at 5 and 7 years were 96.9 and 96.1 percent, respectively, for the combined group vs. 97.6 and 96.2 percent, respectively, for 3D-CRT alone.
  • Low Gleason grade, HDR brachytherapy combined with 3D-CRT, and the use of adjuvant androgen deprivation therapy were significant in predicting biochemical progression-free survival.
  • Late urinary and rectal morbidity rates were 7.1 and 0.0 percent for the combined and the 3D-CRT alone groups, respectively.

The authors conclude that “HDR brachytherapy combined with 3D-CRT was associated with improved [biochemical progression-free survival] and minimal toxicity in patients with unfavorable prostate cancer compared with conventional 3D-CRT.”

The “New” Prostate Cancer InfoLink would at least suggest that it is possible to come to a different conclusion, which is that while HDR brachytherapy added to 3D-CRT does indeed add a small degree of benefit in terms of biochemical progression-free survival (most particularly in the high-risk patients) compared to 3D-CRT alone, this benefit is not evident in either overall or prostate cancer-specific survival rates at 5 or at 7 years, and comes at a relatively significant increase in risk for late urinary and rectal morbidity that is not as evident in patients treated with 3D-CRT alone.

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