HOW LASER IS USED IN TREATING CANCER

1. LASERS IN
ONCOSURGERY
DR.SUNIL KAMBLE
ASSISTANT PROFESSOR
DEPT.OF GEN.SURGERY
MNR MEDICAL COLLEGE,SANGAREDDY

2. History
• Laser principles were first enumerated by the great scientist
Einstein during early part of 20th century.
• First clinical application of laser - Prof.Mommen
• Dr.Issac Kaplan introduced the application of CO2 laser.
• In Gulf war laser guided missiles were used.

3. Introduction
• Laser is an acronym for light amplification by stimulated
emission of radiation.
• A laser equipped device can generate high intensity
monochromatic ,unidirectional, coherent and parallel light.
• The laser energy is a photon ,the basic light component.
• The photon gets charged in a chamber which contains the
laser medium.

6. Components Of Laser Device
1.Active medium
• Solid
• Liquid
• Gas
2 Optical cavity or resonator
3.Energising source or pump

8. Properties of Laser
• Light released is
• Monochromatic
• Coherent
• Directional
• These 3 properties possible by stimulated emission
• Power Density : Laser beam intensity is called as its power
density(Pd)
• Fluence : Is a measure of the total energy
• Prolonged exposure - Tissue destruction
• Short exposure - Inadequate effect
• Wavelength - Degree of absorption and its thermal effect on
skin vary with type of chromophores in the recipient

10. Selective Photothermolysis
• Is a method for localising tissue damage to specific
chromophore targets at the cellular level
• Used to minimise undesired thermal damage to the
surrounding tissue caused by thermal diffusion

11. Collimation
• A laser beam is collinated
• Unlike a flash light,whose beam expands as it travels,the laser
beam maintains a nearly constant diameter whether it is
transmitted 20cm to a surgical patient or 240,000 miles to
communicate with astronauts on the moon
• All the laser power stays concentrated in that small beam to
be absorbed by any no-reflective surface it strikes

12. Monochromacity
• A laser beam has a single optical frequency

13. Coherence
• All the photons comprising the laser beam travel together in a
coordinated fashion
• Because of these properties a laser has a predictable
interaction with tissues which can be intense and focussed on
to a small area
• The fundamental event of photon tissue interaction is either
absorption or scattering of light

14. • Both these phenomenon are interdependent and determine
the light intensity at all points within the tissue
• The laser effect of tissue depends on the
wavelenth,penetration distance,time of exposure,tissue
constituents,density and vascularity of region
• As the tissue gets heated,critical temperatures are
reached,resulting in endothelial damage,cell death,protein
denaturation,blood vessel costriction and eventually tissue
vaporisation

15. Critical temperatures
Temperature Histological event
45°c Cell death;oedema,endothelial damage and vasodilatation
60°c Protein coagulation
80°c Denatured collagen
100°c Tissue water boils
210°c Dehydrated tissue burns

16. • The simultaneous cooling effect of surrounding tissue limits
the damage and is dependent on the intrinsic thermal
diffusion capacity of the tissues and its blood supply
The final effect on the tissues is thus dependent on
Absorption
Reflection and
Transmission
of the laser beam in the tissues at that particular wavelength

17. 2.The power density of the laser beam
3.The speed of incision or the time of exposure
4.The volume and blood flow velocity in local blood vessels
• The degree of tension and the nature of tissue at the area of
incision when cutting i.e. darker or pigmented tissues are
known to absorb more laser energy and therefore sustain
more damage

18. Different media used for laser
production
Media Wave length(nm)
1 Helium-Neon(He-Ne) 632.3
2 Ruby 694.3
3 Argon (Ar) 476.5 to 514.5
4 Kryptonin 476.1 to 647
5 Neodymium (Nd) 1060
6 Nd:YAG (Yttrium-Aluminium Garnet) 1060
7 Carbon-di-oxide(CO2) 10600
8 Helium Cadmium 325 to 441.6
9 Nitrogen 337
10 Dye 337

19. Classification
• Type of laser material used
• Dye lasers
• Semiconductor lasers
• Solid state lasers
• Semi conductor (diode ) lasers
• Dye lasers
• Gas lasers
• Excimer lasers

20. Laser classification by
wavelenth

21. • The optical spectrum .
• The laser light is nonionising and ranges from the
ultrviolet(100-400nm),visible(400-700nm) and
infrared(700nm-1mm)

22. According To Modes
• Continuous wave
• Pulsed
• Q switching
• The light generated with a laser can be delivered in 2 ways
• As a constant flow of energy continuous wave laser
• Or as multiple discrete pulses (pulsed laser)
• Both type of lasers can further be modified to produce even
shorter pulses,usually in the range of 10-250ns,by using Q
switching method

23. • Simplified
representation of
pulse types(2)

24. Laser Tissue Interactions
• Can be characterised as
• Photochemical
• Photothermal
• Photomechanical
• A laser light impinges upon tissue it may be
• reflected,
• absorbed,
• scattered,or
• Transmitted
• Amount of absorption depends on chromophores
• Hemoglobin
• water

25. • Scattering of laser light is caused by skin dermal collagens
• Absorption of laser by the targeted tissues is important
• The part of the tissues that absorb the photons are called
chromophores
• Melanin
• Hemoglobin
• Water
• Laser energy absorbed by chromophores is converted into
heat energy

27. Photothermal Effect
• Hyperthermia
• One of the phtothermal effect is called as hyperthermia
• Involves exposure to a mildly elevated temperature and
effects require at least 24 hours to develop necrosis
• Photocoagualation
• The difference between photocoagulation and hyperthermia
is,photocoagulation requires only a short exposure to a high
temperature and the effects are immediate and visible
• The immediate effect is coagulation of cells and extracellular
collagen

28. • The delayed biological response involves inflammation on
both cellular, and the tissue levels
• The healing response involves activation of fibroblasts to
synthesize collagen with scar formation
Dessication
• Evaporation of water is an important heat sink for laser energy
and steam can carry heat away from the primary region of
laser exposure
• Above an energy of 1 watt , the laser therapy induces
evaporation and the energy is removed from the liver site by
escaping vapor

29. Photomechanical Effects
• Lasers can induce stress in tissues and such mechanisms of
interaction are described as photochemical
• Two types
• Transient stress waves
• Quasi –steady stress waves

30. Photodynamic therapy
• Newer modality in treating very early or late cancers
• The basic technique consists of the systemic injection of a
photosensitising agent (haematoporphyrin) which is
selectively concentrated in cancer cells
• Its subsequent activation by laser beam can lead to tumor
destruction,apparently through disruption of vascular integrity
of the neoplasm

31. • The mechanism by which the blood vessels are destroyed
appears to involve damage to the endothelium,and release of
vasoactive substance including thromboxane
• The normal cells which do not take up haematoporphyrin are
unaffected.
• By this ,laser can selectively destroy the cancer cells
• To destroy cancer cells selectively without damage to normal
cells is the ultimate goal

32. • A large superfi cial
basal cell carcinoma
on the chest,
• (a) before and
• (b) after one episode
of photodynamic
therapy.

33. Transient Stress Waves
• Sudden thermoelastic expansion of tissue caused by rapid
heating by pulsed laser
• Recoil caused by ejection of ablated mass
• Sudden expansion secondary to phase change such as
vaporization of water or formation of plasma (the popcorn
effect)

34. Quasi Steady Stress Waves
• Occurs secondary to the thermoelastic expansion of tissue
caused by thermal heating
• This term used to emphasize that the thermoelastic expansion
is not a transient stress wave but rather a static distribution of
stress that depends on the temperature distribution

35. Types Of Lasers Used In Surgery
• CO2 laser Wavelenth 10,600nm
visibility Invisible
Spectrum Mid infra red
Medium Gas
Watts 50w
Significant
characteristics
Strongest absorption in tissue
Scattering negligible ; light energy converted
into heat at tissue surface
Suitable for removal of tissue & for cutting at
shallow depths
Disadvantage
s
Stopped by 1mm of H20
Focussing of the Helium-Neon beam
Production of smoke referred to as “plume”
Limited use in endoscopy , due to inflexibility

36. KTP-ARGON
WAVELENTH 485nm-515nm
VISIBILITY Green light
SPECTRUM Visible
MEDIUM Gas
SIGNIFICANT CHARACT Tissue absorption less than CO2 but more than Nd:YAG
Thermal action shallower than Nd:YAG
Has application to indications when removal of tissue
with simultaneous localized coagulation is desired
DIADVANTAGES Need to wear special glasses - Distorted view

37. Nd:YAG LASER(Neo –Dymium
Yttrium Aluminium Garnet)
Wavelength 1060nm
Visibility Invisible
Spectrum Near Infrared
Medium Solid State
Watts 100
Sign. characters Contactless & bloodless
Can be used through flexible fibreoptic source
Can be used in water
Suitable for deep thermal work-destruction of tissue without
removal
Optical scattering in tissue considerable - Promotes uniform
distribution of radiation in tissue
Mechanical damage to tissue surface
Disadvantages No use in surgical cutting

39. Oncology
• Used in photodynamic therapy of patients with both
malignant tumours and non-tumoral illness
• Photodynamic therapy involves the absorption of a
photosensitising agent(which interacts with visible
light),retention of the agent in tumour tissue , and selective
laser irradiation of tumour tissues, which were previously
sensitised by dyes.

40. • Laser capture microdissection technique is important tool for
cancer diagnosis and the development of markers for early
detection
• CO2 lasers are used in carcinoma of oral cavity , pharynx and
larynx

41. Early Upper GI Malignancies
• Endoscopic therapy for early gastric carcinoma include
• Ergotherapy
• Laser microwave coagulation
• Resection
• Injection of chemical agents
• Laser therapy can be divided into
• photothermal destruction using a high energy output and
• Photochemical destruction using a low energy output

42. High Power Laser Therapy
• The Nd:YAG laser is invisible because of its long wavelenth of
1064nm
• Hence a HeNe laser is used
• Intermittent radiation by this laser using an output of 40-80
watts and a duration of 0.5-1.0 seconds is carried out
• An endoscope with direct or oblique vision is used

43. Low Power Laser
• Intravenous injection of an oncotropic porphyrin derivative is
given 48-72 hours before divided spot irrradiation with an
argon dye laser
• Laser coagulates tissue selectively with only slight post
treatment changes in the normal tissue
• Cause only slight changes in appearance of any tissue during
irradiation, and the non irradiated tissue may not be readily
distinguishable from the irradiated one, if the lesion is large
• Hence early gastric cancers that are obscurely demarcated are
good indicators for low output laser therapy

44. • Laser therapy for early gastric cancers can replace
conventional surgical therapy .
• Requirements
• Lesion must be a very early cancer wothout lymph node
metastasis
• Operator proficiency

45. Laser Therapy For Colorectal
Carcinoma
• Photoablative laser therapy for advanced GI malignancy as
palliative measure
• Endoscopic palliation - Photodynamic therapy
• Introduction of medical lasers with endoscopic equipment has
led to photoablative laser therapy as the treatment of choice
in patients with advanced GI malignancy and in patients who
refuse surgery
• Widely metastatic or unresectable disease
• Concomitant medical illnes that will prevent surgical
intervention

46. Endoscopic Nd:YAG Laser
Therapy :Photoablative
• Preresectional laser therapy : Laser recanalization is possible
prior to resection of obstructing left sided colorectal tumours
• Lesion is traversed and then photo ablated as the endoscope
is removed until the flexible sigmoidoscope or colonoscope
can easily pass in and out
• Within 24 hours, a bowel wash is given followed by elective
resection with primary anastomosis

47. Palliative Laser Treatment
• In patients with advanced disease
• Hemorrhage,obstruction,tenesmus are presenting features
• Probale complications
• Perforations
• Strictures
• Hemorrhage
• Photodynamic laser therapy
• Beneficial in patients presenting with bleeding and bulky
lesions

48. Lasers In Liver Surgery
• Selective Photovaporization Of Tumors
• Liver is mobilized to obtain total exposure, and capsule is
scored with cautery in a circular fashion directly over the
lesion
• This is base of cone dissection
• Apex of cone dissection is the metastasis to be treated
• Once the lesion is explored ,one can vaporize it safely under
direct vision
• Nd:YAG laser with a bare fibre , in continuous mode is used
• Special smoke evacuator is used to remove pungent laser
plume
• A margin of 1 to 1.5cm normal tissue is included in the field of
vaporization to ensure adequate margins

49. Interstitial Therapy Or In Situ Ablation
Of Intrahepatic Malignancies
• Cryosurgery
• Alcohol injection
• Laser ablation
• Laser hyperthermia
• Electrodissection
• Interstitial radiation implantation

50. Interstitial Laser Hyperthermia
• Light administered by Nd : YAG laser could deliver energy at
the tip of a transmission fibre placed interstitially
• With percutaneous ethanol injection, the laser fibres can be
inserted via percutaneously placed 14 gauge needle
introduced under ultrasound guidance
• In general , using Nd:YAG laser , the power applied ranged
from 500-1000 seconds
• To prevent injury to surrounding structure ,coaxial gas flow in
the range of 1L/min is used to provide cooling

51. MRI Guided Laser Induced
Interstitial Thermotherapy
• Is a percutaneous,minimally invasive treatment modality for
treating liver lesions/metastases,soft tissue tumors and
musculoskeletal lesions
• Nd:YAG laser (1064nm wavelenth) used for tumor ablation
• MRI using both open and closed MR units is effective in
validating the exact positioning of optical fibres
• Allows for early detection of local complications and
treatment effects,such as bleeding or necrosis

52. Laser Induced Interstitial
Thermotherapy(LITT)
• Is a minimally invasive , local form of treatment,the
coagulative effect of which lead to tumour destruction in solid
organs
• Near infra red lasers are used
• LITT permits selective photothermal tumour destruction
which preserves surrounding parenchymatos organ structure

53. Lasers In Neurosurgery
• Most surgical effects of laser light on neural tissue and CNS
are thermal lesions
• CO2 and Nd:YAG lasers are used
• Stereotactic neurosurgery
• Resection of acoustic neuromas,pituitary tumors,spinal cord
neuromas,intracerebral gliomas and metastases
• Reduce surgical trauma to brain,brain stem,cranial nerves
• Any fibre optic guided laser can be used
• LITT and photodynamic therapy are still in experimental stage

54. • Contact laser used for destroying tumours , coagulation of
blood vessels, restoration of patency to main arteries,
interstitial denaturation of gliomas and denaturation of the
nucleus pulposus in lumbar vertebral column
• Lee Eric Tessler a neurosurgeon,is first one to use a new
advanced , hand held CO2 laser for surgeries
• Laser allows surgeons to remove difficult to reach tumors in
less time , with lower risk of complications,less anesthesia

55. Selective Cancer Therapy Using
IR-laser Excited Gold Nanorods
Application of nanoparticles includes
Bioimaging
Biosensing,
Drug deliver cancer cell diagnostics and therapeutics
By changing the shape of nanoparticles from spheres to
nanorods,the absorption or scattering wavelenth changes from
the visible to the near-IR region and offers advantage of much
deeper penetration
Recent studies have shown that gold nanorods attached to
antibodies and viral vectors could be used for selective
photothermal therapy , selective destruction of malignant cells

56. Safety considerations in laser
surgery
• Only trained personnel
• Testing of instrument prior to its application
• Safety and the CO2 laser
• Protective glasses
• Doors to the operation room should be locked
• Laser caution signs should be posted
• Silastic reinforced tube that is wrapped with overlapped
aluminium tape is used for intubation

58. • The appearance of
the externally
applied Durette
Oculo-Plastik eye
cups worn over the
eyelids during laser
surgery performed
closed to periorbital
area(10)

63. • PVC endotracheal tube should not be used
• Nitrous oxide should not be used
• Blackened instruments to prevent full reflection of the laser
beam
• When the CO2 laser is used in the colon or in the area of any
other flamable gas,a noncombustible gas ( most likely CO2) is
used to prevent explosion

64. Safety and the Nd:YAG Laser
• Difficult to use
• Protective glasses
• Restricted access to ot
• Warning signs
• Precaution against fire
• Notrous oxide for anesthesia should not be used

65. Safety and the Argon Laser
• The Argon laser requires colored eye protection in the
orange/yellow range

66. Take home message
• The potential of laser is ever expanding
• Its destructive energy has now being controlled to the benefit
of mankind

67. 1.Recent advances in surgery volume-2 by Roshan Lal Gupta
2.Rooks’stextbook of dermatology 8th edition
3.Recent advances in surgery volume-5 by Roshan Lal Gupta
4.Surgical Clinics Of North America June 1992
5.Surgical Clinics Of North America April 2011
6.Bailey and Love short practice of surgery-26th edition
7.Sabiston textbook of Surgery , 20th edition
8.Schwartz textbook of Principles of Surgery, 10th edition
9.Principles and Practice of Oncology, De Vita, 9th edition
10.Laser dermatology by David J.Goldberg