Tuesday, August 30, 2016

Better cancer control with radiation vs. surgery in high-risk patients

Researchers at the University of Alabama at Birmingham assigned high-risk patients to receive either external beam radiation therapy with androgen deprivation therapy (RT+ADT) or to receive surgery (RP) with or without adjuvant/salvage radiation. RT+ADT was the clear winner. It’s not a randomized trial, and it is small and retrospective, but it’s worthy of note nonetheless.

Baker et al. reported on 121 patients treated between 2001 and 2014 who were diagnosed with Gleason scores ≥8 (on either biopsy or pathology). 71 patients received RT+ADT according to the following protocol:
  • ·      75-77 Gy in 40-42 fractions or 70 Gy in 28 fractions
  • ·      All received pelvic lymph node radiation
  • ·      Almost all (96%) received ADT for 24 months
  • ·      1 patient received adjuvant docetaxel

50 patients who had life expectancies ≥ 10 years, no serious comorbidities, and whose prostate were considered resectable, were offered radical prostatectomy instead of radiation. All patients were seen by both a urologist and a radiation oncologist. Of the 50 RP patients:
  • ·      76% also had pelvic lymph node dissection
  • o   8±6 lymph nodes were sampled
  • o   18% had positive lymph nodes
  • ·      88% had adverse pathology: positive margins, seminal vesicle invasion, or extraprostatic extension
  • ·      74% were stage T3 at pathology (vs. 4% pre-RP)
  • ·      84% were GS≥8 at pathology (vs. 63% pre-RP)
  • ·      44% received adjuvant radiation
  • ·      24% received salvage radiation
  • ·      Those with positive lymph nodes received salvage pelvic radiation
  • ·      1 patient received adjuvant docetaxel

After average followup of 74 months for those who originally received RT+ADT and 60 months for those who originally received RP, the 5-year biochemical failure rate was:
  • ·      7% for those originally receiving RT+ADT
  • ·      42% for those originally receiving RP

The 5-year detection of distant metastases was:
  • ·      2% for those originally receiving RT+ADT
  • ·      8% for those originally receiving RP

The 5-year use of salvage (permanent) ADT was:
  • ·      8% for those originally receiving RT+ADT
  • ·      34% for those originally receiving RP

While the researchers did not report on toxicities, it is safe to say that those who received original RP suffered worse toxicities. This is true not only because surgery carries greater risk of incontinence and impotence, but also because 68% of those who originally received surgery received radiation on top of that, and half of those men received ADT with their adjuvant/salvage radiation. Adjuvant/salvage radiation has a worse toxicity profile compared to primary radiation.

The results in favor of initial radiation therapy are particularly impressive because radiation patients in this study had more progressed disease at the time of treatment. They had higher Gleason scores, higher stage, and higher risk of lymph node involvement. They were also considerably older. The results are all the more impressive because the amount of radiation given was low by today’s best practice standards, and because combination therapies of external beam radiation with a brachytherapy boost to the prostate have been proven superior to external beam monotherapy in randomized clinical trials. If anything, the selection bias and treatments in this study should have favored those who were initially surgically treated.

On the other hand, it’s been demonstrated that the limited pelvic lymph node dissection of the surgery patients given in this study is often inadequate to detect the full extent of involvement. They note that they have recently changed their protocol to include extended pelvic lymph node dissection (ePLND) on high-risk RP patients. Sometimes ePLND not only detects the extent of involvement, but may also clear the area of cancer without the need of salvage nodal radiation.  Two additional caveats are that the difference in definitions of biochemical failure and the two years of ADT may affect relative outcomes. However, it is hard to imagine that the long-term effects would enough to change conclusions given the magnitude of the difference.

While this is not the large-scale prospective randomized trial of RT vs. RP that we would like to see, the large variance in outcomes should be considered by anyone trying to decide between radiation and surgery for a high-risk diagnosis.

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