Development of a more sensitive method to predict breast cancer recurrence after 5-years of endocrine treatment making use of diagnostic leukapheresis to detect circulating tumor cells

Adjuvant endocrine treatment (ET) for 5 years is standard for patients with
primary hormone receptor positive (ER+) breast cancer. However, recurrences
still occur, of which more than 50% occur after 5 years ET. Extended adjuvant
endocrine therapy (EET), up to 10-15 years, increases disease free survival
(DFS). However, there is no robust biomarker predicting late recurrence risk
after 5-years ET. The measurement of circulating tumor cells (CTCs) as a
reflection of residual disease could possibly serve as such a biomarker. Recent
studies showed the prognostic value of CTC enumeration in ER+ lymph node
positive (N+) primary breast cancer patients during and after ET.
Unfortunately, the classic CTC enumeration method using 7.5 mL of blood is not
sensitive enough as disease recurrence also occurred in patients without
detectable CTCs. To measure residual disease through more sensitive CTC
detection, screening of a larger blood volume is desired. CTC enumeration in 30
mL of blood yielded a higher percentage of patients who had >=1 CTC than in 7.5
mL of blood, which increases sensitivity and specificity. However, the
robustness of this test is weak due to stochastic variation inherent to the low
CTC numbers found.
A technique to greatly increase the screened blood volume is called Diagnostic
Leukapheresis (DLA). During DLA, 2.5-5L of blood is passed through a
centrifuge, which isolates peripheral blood mononuclear cells (PBMCs) as well
as CTCs from the blood, which is returned to the patient. Preliminary results
have shown that this procedure increases the sensitivity of CTC detection
substantially by 500-1000. We therefore hypothesize that CTC detection through
DLA improves the detection rate among ER+, N+ primary breast cancer who have
received 5 years of adjuvant endocrine therapy and will be a promising
technique for risk classification in this patient group.

The primary objective of this study is to demonstrate that our DLA-based method
is promising enough to detect CTCs in ER+, N+ primary breast cancer patients
after 5 years ET. Simultaneously, other methods (CTC detection in 7.5 ml and
30 ml of blood as well as ctDNA detection) will be assessed in this study
population and explored how they compare with our DLA-based approach in terms
of tumor load detection.

This is an observational, biomarker study using a Simon-two- stage design

All patients will be asked to undergo a single leukapheresis procedure which
will take a maximum of 2 hours. A maximum volume of five litre peripheral blood
will be processed with the use of an Optia Spectra Cell Separator. Patients do
not benefit from this study. The most common adverse events to be expected are
pain or bruising at the venipuncture site (1-5%), apprehension or fainting
associated with venipuncture (1-5%) and citrate anticoagulant infusion-related
symptoms resulting in tingling or buzzing around the mouth or fingers (20-50%).
To prevent the latter, all patients will receive intravenous calcium, which
reduced the incidence of citrate-related effects by 65 percent in a randomized
trial performed by Buchta et al. An infrequent adverse event is fluid imbalance
(0.01-0.1%, more likely to occur during long procedures). Specialized
apheresis-nurses are trained to recognize and act upon this complication.
Hypotensive or vasovagal reaction will be treated in the standard manner by the
attending medical officer. The risk of adverse events associated with LA is
considered negligible.