Circulating tumor cells in metastatic breast cancer: timing of blood extraction for analysis.
OBJECTIVE
Circulating tumor cells (CTCs) can be detected in the peripheral blood of around 50% of patients with metastatic breast cancer. Their numbers are an independent predictor of the patient's progression-free survival (PFS) and of overall survival (OS). However, to date, none of the studies carried out with the most commonly used system of CTC determination (the CellSearch System, approved by the US Food and Drug Administration) has examined the intra-patient variation in CTC numbers, a variation that could impact on prognosis assessment.


METHODS
To evaluate possible circadian variations in the number of CTCs in patients with breast cancer a pilot study was conducted in which these cells were quantified 12 h apart (at 8:00 a.m. and 8:00 p.m. of the same day) in a cohort of hospitalized patients with metastatic breast cancer.


RESULTS
Out of the 58 patients included in the study, 51 were evaluable. No statistically significant differences between day-time and night-time CTC numbers were observed (p=0.8427, Wilcoxon matched pair test). Only two of the patients were classified in different prognostic categories in the morning and night determinations (5 or more CTCs=poor prognosis group; <5 CTCs=good prognosis group). The prognostic classification of the remaining 49 patients was the same at 8:00 a.m. and 8:00 p.m.


CONCLUSIONS
The number of peripheral blood CTCs in metastatic breast cancer patients is not significantly different at 8:00 a.m. from that at 8:00 p.m. and, as such, indicates a lack of circadian rhythm with respect to CTC numbers in these patients.
Medical Oncology Service, Hospital Universitario San Carlos, Madrid, Spain. mmartin@geicam.org
Miguel
M
Martín
José Angel
JA
García-Sáenz
Maria Luisa
ML
Maestro De las Casas
Marta
M
Vidaurreta
Javier
J
Puente
Silvia
S
Veganzones
Laura
L
Rodríguez-Lajusticia
Virginia
V
De la Orden
Belén
B
Oliva
Julio-César
JC
De la  Torre
Sara
S
López-Tarruella
Antonio
A
Casado
Javier
J
Sastre
Eduardo
E
Díaz-Rubio
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000097:blood* / Q000473:pathology*; D016022:Case-Control Studies; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D010865:Pilot Projects