SBRT as focal treatment for isolated, nodal metastasis

A group of Italian researchers has reported preliminary clinical experience of the use of stereotactic body radiation therapy (SBRT), using CyberKnife technology, in the treatment of isolated, nodal metastases as a consequence of prostate cancer. These are clearly “pilot” data, and patients were not being treated as part of any established clinical trial. However, the data are interesting.

Detti et al. report as follows:

  • The study included 30 patients with a total of 39 nodal metastases.
  • All patients were treated between November 2011 and December 2013.
  • Treatment varied from patient to patient.
    • The most common treatments were
      • 30 Gy in three fractions on alternating days
      • 36 Gy in three fractions on alternating days
    • The range of treatments used was from 24 Gy in one fraction to 36 Gy in three fractions.
  • Average (median) follow-up was 12 months (range, 2.0 to 24.9 months).
  • Post-treatment effects on PSA levels are reported as
    • A significant reduction in PSA among 24 patients
    • A stable PSA for 1 patient
    • An elevated PSA among 9 patients
    • Note: These data cannot all be correct since there were only 30 patients included in the study!
  • At the time of analysis
    • 2/30 patients (7 percent) had died from systemic prostate cancer
    • 12/30 patients (40 percent) had exhibited a prostate cancer progression other sites.
    • 16/30 patients (53 percent) were still free of disease.
    • No in-field recurrence was evident among 24 patients among whom imaging evaluation was carried out at 3 months post-treatment.
  • SBRT appears to have been well tolerated.
    • No patients exhibited acute or late toxicities of Grade 3 or higher.
    • 1/30 patients (3 percent) experienced acute, Grade 2 genitourinary toxicity.
    • 1/30 patients (3 percent experienced late, Grade 1 protitis (at 6 or more months of follow-up).

The authors conclude that, based on their experience,

SBRT for isolated nodal relapse from prostate cancer is a safe treatment, with promising results in terms of efficacy.

One Response

  1. It is strange that their numbers don’t add up. Many of the same authors at the University of Florence published a study last year of both men and women treated for abdominal lymph node metastasis, and reported good short-term control, especially among tumors of prostatic origin.

    At the University of Milan, 69 patients (men and women, various cancers) were treated for single abdominal lymph node recurrence with SBRT — 24 Gy; three fractions. (Although they say it was a single lymph node, they treated 94 lesions, and evaluated 81 lesions.) Half the patients received systemic therapy also. After a median follow-up of 20 months, they observed:

    — Complete radiologic response in 44% of lesions,
    — Partial response in 26% of lesions
    — Stabilization in 25% of lesions, and
    — Progressive disease in 5% of lesions

    Focusing on prostate cancer, 83 patients with lymph node-only relapse (pelvic, abdominal, and other sites) identified via [11C]choline PET/CT were treated with hypofractionated tomotherapy at the San Raffaele Scientific Institute, Milan, Italy. 47 patients were re-evaluated by PET/CT after treatment:

    — 20 (43%) showed a complete metabolic response at the treated area
    — 22 (47%) showed a partial metabolic response
    — 2 (4%) showed stable disease
    — 3 (6%) showed progression of disease
    — 8 patients (10%) were re-treated once or twice

    These small Italian studies are intriguing because they open up the possibility of a cure after nodal relapse. However, they leave many questions unanswered:

    — What is the long-term survival benefit? What percent are truly oligometastatic?
    — How good are current diagnostic methods (e.g., PET or USPIO MRI) at identifying nodal-only recurrences?
    — What is the optimal target for nodal recurrence — the single node, the nodal string, or the entire pelvic field, and what is the toxicity associated with widening the field?
    — Is there a benefit to using ADT and immune-boosters to enhance the radiological response?

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