Magnetic Marker Localization for breast cancer surgery: An exploratory study

All currently available tumor localization techniques for non-palpable tumors
during breast conserving surgery have obvious drawbacks. Wire-guided
localization has a low accuracy, is painful and comes with challenging
logistics. Radioactive alternatives such as radioactive seed localization (RSL)
or Radioactive Occult Lesion Localization (ROLL) were limited implemented in
daily practive clinic because of strict regulations and protocol requirements
that come with the implementation of a new radioactive technique. Also,
ultrasound-guided localization during the surgery has the disadvantage that it
is challenging due to the required presence of a radiologist, or a trained
surgeon, which is time-consuming and bears logistic challenges. Three quarters
of patients are still treated with a suboptimal technique, therefore, the
development of new techniques is imperative. Our group started to investigate
the use of magnetism for tumor localization, analogue to RSL. A new,
radiopaque, magnetic marker was developed, which can be implanted in the tumor
up to 30 days before surgery. This marker can be accurately detected during the
operation by using a commercially available portable magnetic probe which
functions as a gamma probe. The advantage of using magnetism is the omission of
the use of radioactive material and the accompanied regulations and protocol
requirements. Also magnetism does not decay over time. In previous studies, the
magnetic marker and detection characteristics have been developed and validated
in a laboratory environment, and proof-of-principle was obtained in ex vivo
animal and human tissues. A study in15 breast cancer patients demonstrated that
this technique is feasible and safe, and that further research is fully
warranted. Up till now, the experimental MaMaLoc technology was combined with a
"fall-back" localization method (radioactive seed localization). Now with the
demonstrated feasibility and safety, the magnetic localization technique will
be investigated as sole localization technique. The purpose of this study is to
investigate surgical usability, patient-reported outcomes and efficacy of the
experimental magnetic technieque and to compare it with the worldwide gold
standard (wire-guided localization) in a larger pilot study. The data collected
in this study will be used to adequately power a randomized controlled trial .

The purpose of this clinical study is to investigate surgical usability,
patient-reported outcomes and effectiveness of the MaMaLoc technique and
compare it with WGL.

Pilot prospective cohort study

Subjects will be randomly assigned to either the first (control) or second
(intervention) group by means of drawing an envelope. Wire Guided Localization
is the current standard of care. With the MaMaLoc technique the magnetic seed
is implanted in or near the breast lesion by the radiologist, after local
anesthesia. During surgery the seed will be detected with a magnetic detector.
After surgery, it will be confirmed that the magnetic seed is removed with the
detector, as well as during pathology analysis. The further process is
identical to standard care.

Burden for patients is similar in the intervention group compared to the
standard of care (WGL). Placement of a wire (WGL) is replaced by placement of a
magnetic marker (MaMaLoc). The only additional burden for all participants is
to fill out a questionnaire on two occasions: around the localization process
and after surgery. This takes about 10 minutes in total. Patients risks are
minimal. Eligible patients in the intervention group that already have a
separate biopsy site marker in situ to use as a reference (max N=10) will
undergo one extra mammography to assess MaMaloc marker migration (0.2 mSv total
dose). Detection using low field magnetism is inherently safe and the marker is
constructed from biocompatible materials. In vivo studies in fifteen patients
have already demonstrated the safety and feasibility of the technique. The
benefits of this research definitely outweigh the burden/risks for patients .