Lecture 16: Advancing Tumour Surgery through the Enhancement of Intraoperative Precision

what is cancer?

Cancer (neoplasia) occurs when abnormal cells divide in an uncontrolled way. Some cancers may eventually spread into other tissues (metastasis).

Types of cancer treatment

• Surgery- heavy reliance

• Radiation Therapy

• Chemotherapy

• Immunotherapy to Treat Cancer

• Targeted Therapy

• Hormone Therapy

• Stem Cell Transplant

• Precision Medicine

Tumour Architecture

• The accurate definition of surgical resection margins is an critical prognostic factor in cancer surgery

• 40% of cancers treated following removal of “tumour margin with clearances”

• Positive and Negative margins have consequences

  • +ve = residual cancer on edge of surgical resection

  • -ve = cancer contained inside surgical resection

• Margins currently defined by sight and feel

• Unmet clinical need

Current Intra-operative Imaging Solutions

1. biopsy: tissue dehydrated and mmbeded in parafin

2. Microtome: cut into wafer thin section

3. attach to slide

4. remove wax

5. stain tissue

Frozen Sectioning - Cryostat

• to speed up tissue processing

• deep freeze tissue instantly to cut tissue

• 30-40min

Cons of cryostat

• Poor quality section: Frozen tissue sections are not easy to cut compared to paraffin embedded sections (especially brain and other fatty tissues)

• Bloated cell morphology: Tends to cause the cells to be larger and appear (water freezes)

• Poorly stained section: As pathologist depends on colours as well as morphology, studying cells and its surrounding tissues, this factor may affect diagnosis bloated

paraffin embedded vs frozen tissue section

paraffin:

• fixed tissue

• time consuming:24-48hrs

• clear morphology

• pathological diagnosis

freezing:

• fresh tissue

• 30-40 mins

• opaque morphology

• intraoperative consultation

Fluorescence Based Imaging

• Fluorescent compound absorb (λex) and emit light (λem) at specific wavelengths

• Stokes Shift: the difference, in nanometres, between the peak excitation and the peak emission wavelengths

  • must have good peak separation to avoid overlap and confusion

• Each fluorophore has a distinct and individual Stokes Shift

Method for Fluorescence Based Imaging

1. white light shined through filter to select specific wavelength

2. light hits dichroic mirror

3. reflects light of certain wavelength onto sample

4. sample fluoreses and is detected

Fluorescence Guided Surgery

• patient given fluorophore to bind to tumour cells

• Fluorescent dyes (ICG) are not tumour specific – false positives

Diathermy Cutting Blade

• The iKnife: not in clinical practice

  • food industry

• Diathermy cutting blade used in surgery to minimise intraoperative bleeding - hot blade cauterises blood vessels

• major byproduct = smoke

  • previously been considered to be a toxic irritant – extracted to waste

  • authors suggest that this is a rich source of biological information

  • used mass spectrometry to measure the metabolomic composition of this vapour

  • could provide new chemical information that describes the tissue and its associated pathology

diagnosic markers in smoke

• Glycerophospholipids are overexpressed in all cancers

• degree of of over expression can determine cancer type

• The basic structure of important phospholipids detected during MS vapour analysis

limitations to diathermy smoke suction

• Slow in sergery (30-60secs per analysis)

• Expensive due to mass spectrometer

• Not all procedures use a diathermy cutting blade

MarginProbe™

• Dune Medical Devices

• currently used in lumpectomy in breast cancer

• Assessment of malignant margin residue on tumours removed from patient

• Radio wave base assessment of cells pathophysiology

MarginProbe™ method

1. sergion removes lump of tissue

2. tissue analysed using radio waves

3. cancer contains more water than healthy

4. technition uses probe to emit radiowaves

5. radiowaves detect water and determine if tissue is malinant or normal

Pros and cons of MarginProbe™

pros:

• Rapid, reagent free response

• Additional surgical information to prevent secondary operations

cons:

• measuring on tissue outside the patient

• Tissue analysis rather than informing surgical decision making – Reason for quick FDA approval?

FLARE™

• Fluorescence-Assisted Resection and Exploration is based on the use of a Near Infrared (NIR) fluorophore (Methylene blue) to detect tumour cells

• Provides real-time guidance to surgeons for targeting tissues of interest and avoiding sensitive structures

• Methylene blue injection at sight of tumour provides NIR ‘contrast reagent’

NIR Fluorescence Guided Surgery

1. give patient methylene blue

2. illuminate patient with white light and NIR

3. NIR causes tumour cells to fluoresce

4. detected by camera

FLARETM Limitations

• Fluorophore is not tumour specific

• Whole of abdomen is illuminated – reduced signal strength and tissue penetration

• Reduced surgical precision?

Pathology Node - Biomedical Engineering Strand Objectives

• ‘To develop a technique or process based on Near Infrared (NIR) technology that would allow the direct, real-time intraoperative definition of tumour margins’.

• Identify a tumour-cell specific target molecule that could be labelled with an antibody based NIR fluorophore

• Miniaturise existing NIR sensor technology into a hand-held sensor for intraoperative use

• Use the hand-held sensor to detect NIR labelled cell in vitro and in vivo

  • scalpel with NIR light source to fluoresce tumour cells

Selection of a Novel Target – Protein Expression Array Data

• in colorectal cancer, tumour regrows at junction of tissue removed - scar tissue

• protein expression array data

• control: CCD-841

• colon cancer: HT-29

• EpCAM over expressed in cancer cells - use anti-EpCAM as AB

Conjugated Polymer Nanoparticle (CPN®)

• Significantly brighter than ‘organic fluorophores’ (based on OLED technology)

• Long-term photostability (years)

• Multi-modal imaging potential

• Biocompatibility

• Familiar surface ligand chemistry

• λex= 750nm – λem=1125nm

NIR Sensing Technology

1. Reece innovation: use NIR to detect cracks in wind turbine > Collimator to focus light cell to a point

2. Sagitto: handhelt NIR sensor > can detect EpCAM expression > use glasses

CPNs have Theranostic Potential

• drug can be therapeutic and diagnostic

• Tumour selective intraoperative imaging

• NIR Responsive ROS medicated Tumour Destruction through the initiation of Apoptosis

• shrink tumour mass before surgery

Market analysis

• iKnife – Imperial College, London, UK.

• FLARE™ IntraoperativeNear-Infrared Fluorescence Imaging System – LUMC, Netherlands

• LightOx – Billingham, UK.

Patent Position

1. Choice of NIR CPN – if unique

2. Choice of tumour marker antibody – if unique

3. Combination of the two

4. Novel imaging system, if sufficiently innovative

5. Novel integration of imaging system with surgical procedure, again if sufficiently innovative