The diagnostic utility of the flare phenomenon on bone scintigraphy in staging prostate cancer.
OBJECTIVE
Bone scintigraphy (BS) lacks sensitivity for detecting very early skeletal metastases (SM) in prostate cancer (PC) and is often limited by poor specificity. Also scintigraphic flare of SM can occur following effective treatment and mislead an early response assessment. We hypothesised that a flare reaction might amplify the signal from subclinical SM, increasing the sensitivity of BS and that the phenomenon may be specific for metastases.


METHODS
We conducted a prospective study to determine the frequency of the flare phenomenon in patients with metastatic PC starting hormone therapy and to explore its utility in patients with negative staging scans but considered at high risk of SM and in those with equivocal baseline BS abnormalities. Ninety-nine patients commencing first-line hormone therapy had repeat BS at 6 weeks to score a flare reaction.


RESULTS
Of 22 patients with unequivocal SM on the baseline scan, a flare occurred in 9 (41%). Of 36 high-risk localised prostate cancer patients with normal BS pre-treatment, the scan became positive for metastases at 6 weeks in 4 (11%). Of 41 patients with pre-treatment scintigraphic abnormalities of uncertain aetiology, a flare occurred in 8 cases (20%). All eight were confirmed to have SM by follow-up and imaging. Of the 33 remaining patients without a flare, 2 developed SM at 14 months and the remainder did not develop SM in a median follow-up period of 36 months.


CONCLUSIONS
The flare phenomenon following initial hormone therapy can be used to improve both sensitivity and specificity of BS in PC.
Cook
Gary J R
GJ
Department of Nuclear Medicine and PET, Royal Marsden Hospital, Downs Rd, Sutton, Surrey, SM2 5PT, UK. gary.cook@rmh.nhs.uk
Venkitaraman
Ram
R
Sohaib
Aslam S
AS
Lewington
Valerie J
VJ
Chua
Sue C
SC
Huddart
Robert A
RA
Parker
Christopher C
CC
Dearnaley
David D
DD
Horwich
Alan
A
D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D006728:Hormones / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity
D006728:Hormones