Worsening bone scan in the evaluation of antitumor response during hormonal therapy of breast cancer.

Purpose: Scintigraphic flare in association with response to therapy has been well described in the medical literature. During the course of a recent breast cancer trial, it became apparent that several patients with worsening bone scan but no other clinical evidence of disease progression might have potentially benefited from continued therapy, but had therapy discontinued. A retrospective analysis of this issue was performed to assess the magnitude and scope of this problem.

Materials And Methods: A total of 648 patients with hormone receptor-positive or unknown advanced breast cancer were treated as part of a large-scale trial of first-line hormonal therapy. Patients were assessed for response to therapy, including response duration, progression-free interval (PFI), overall survival, and quality of life. The retrospective analysis presented here was performed to assess whether patients with a possible scintigraphic flare within the first 16 weeks of therapy might have had therapy discontinued prematurely due to a worsening bone scan attributable to tumor flare, rather than due to disease progression.

Results: Analysis of the hormonal trial showed that of 376 assessable patients 108 (29%) with bone disease had a possible scintigraphic flare by week 8 or 16 of the trial, based on data on the case report forms and radiology reports (bone scans and x-rays). Of these, 69 patients (64%) were continued on study therapy, which resulted in clinical benefit in 50 (72%) of those patients. In contrast, 39 patients (36%) with possible scintigraphic flare were removed from the trial.

Conclusion: We conclude that changes in bone scintigraphy that mimic progressive disease early in the course of hormonal treatment of patients with breast cancer metastatic to bone may represent scintigraphic flare associated with response. Thus, clinicians must be cognizant of the phenomenon of scintigraphic flare to avoid premature discontinuation of a potentially beneficial treatment.