Abstract 303P
Background
Most current guidelines do not recommend determination of CA 15.3 in the follow-up of asymptomatic patients treated for early breast cancer. These guidelines are based on few, small-scale studies performed in an era with more limited treatment options than today. In the University Hospitals Leuven (UHL), CA 15.3 has been systematically used for decades in the follow-up of early breast cancer while staging imaging was only performed on indication.
Methods
Eligible patients for this retrospective single-centre study were treated for early breast cancer at the UHL between 1-1-2000 and 1-1-2018, diagnosed with secondary metastatic disease at least 6 months after initial surgery and had CA 15.3 available at the moment of diagnosis of metastases. The primary objective was to evaluate in how many asymptomatic patients the diagnosis of secondary metastatic disease was discovered by an increasing CA 15.3. Other triggers that could lead to the diagnosis were history, clinical examination, other lab changes or incidental findings. Information about the diagnostic process, evolution of CA 15.3 and survival was collected from individual medical files after approval of the ethical commission.
Results
We included 730 patients. In 237 patients (37%) an increasing CA 15.3 was the first sign that gave rise to the diagnosis of metastatic disease. This was most frequent in luminal A-like subtype (49%) and in liver and bone localisation of metastases (45% and 41%). At the moment of diagnosis of metastases, 451 patients (62%) had CA 15.3 levels above the upper limit of normal (ULN, >30 kU/l). In 502 patients (69%) a CA 15.3 increase of more than 50% was noticed compared to the lowest value measured between 6 months after treatment of primary breast cancer and moment of metastases. The median overall survival was not significantly different in patients with metastases detected by an increasing CA 15.3 versus other triggers: 28 months (95% confidence interval (CI) = 26-33) versus 23 months (95% CI = 19-28) with p-value 0,2.
Conclusions
When CA 15.3 is systematically used in the follow of asymptomatic early breast cancer patients, the diagnosis of secondary metastatic disease is made in 37% by a CA 15.3 increase. CA 15.3 is elevated above ULN in 62 % of secondary metastatic patients at the moment of first metastases.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Hans Wildiers.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.