Bone scan “flare” associated with treatment with abiraterone acetate


A new paper in Clinical Cancer Research indicates that at least some men will have a short-term bone scan “flare” as a consequence of initiation of treatment with abiraterone acetate. The clinical significance of this flare is still to be fully evaluated.

Ryan et al. — in a small, Phase II clinical trial — used abiraterone acetate to treat 33 men with chemotherapy-naïve, castration-resistant prostate cancer (CRPC).

The patients all received abiraterone acetate 1,000 mg daily with prednisone 5 mg twice daily in continuous 28-day cycles. They were evaluated clinically every month. The goal was to assess bone scan data that did not seem to correspond to PSA and clinical response data.

For the purposes of this study, a bone scan flare was defined as the combination, after 3 months of abiraterone therapy, of a radiology report indicating “disease progression” in the context of a PSA decline of  ≥ 50 percent, with bone scan improvement or stability 3 months later.

The results of the study showed the following:

  • 22/33 patients (67 percent) had a PSA decline of ≥ 50 percent at week 12.
  • 26/33 patients (76 percent) had a PSA decline of ≥ 50 percent overall.
  • Undetectable PSA levels (≤ 0.1 ng/ml) were documented in two patients.
  • Average (median) time on therapy was 63 weeks.
  • Average (median) time to PSA progression was 16.3 months.
  • 23/33 patients (70 percent) were evaluable for bone scan flare.
    • 12/23 evaluable patients (52 percent) showed disease progression on bone scan, as indicated in radiologists’ reports.
    • 11/12 patients showing signs of progression subsequently showed improvement or stability.
  • As defined above, bone scan flare was observed in 11/23 evaluable patients (48 percent) or 11/33 enrolled patients (patients).
  • Adverse events to abiraterone therapy were typically grade 1/2 and were consistent with adverse events in prior published reports.

Ryan and his colleagues conclude that although clinical responses to abiraterone + prednisone are frequent and durable in men with metastatic CRPC, we need to clarify the impact of bone scan flare on patient management and interpretation of results.

One has to wonder whether short-term use of an antiandrogen like bicalutamide just before and through the time of initiation of abiraterone therapy might help to suppress this bone flare reaction, just as it does with the initiation of LHRH agonist therapy.

4 Responses

  1. The flare reaction is a known phenomenon in general following chemotherapy and has been reported after radiation therapy also. The important lesson is for the physician (nuclear medicine specialist like me, or radiologist) to recognize it and take it into account in his or her report of the bone scan.

  2. With the question of whether short-term antiandrogen prior to and with initial administration of abiraterone would prevent bone “flare” … I don’t have any idea, but what does come to mind is if the patient has failed ADT and likely androgen receptor mutation (ARM) has occurred, the administration of an antiandrogen, that now becomes a fuel to PC cell growth, may hamper abiraterone effectiveness.

  3. My husband’s first month on abiraterone brought his PSA down from 7 to 3, no symptoms. The second month, it soared back up to 12. Bone scan shows some progression. Wondering if it could be “flare” from the abiraterone. He has some mild bone pain, but we attribute that to Zometa which he has been on for a while.

  4. Dear Claire:

    Could the rise in the PSA be flare associated with the abiraterone? Yes, perhaps, … but what does your husband’s medical oncologist say?

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