Carbon Dioxide Laser Treatment of Cervical
Dr. T.H. Cheung, MRCOG microslad under colposcopic vision. This allows a
Medical Officer, O&G Dept precise control of the extent and depth of tissue
Prince of Wales Hospital destruction, so that extensive lesion and lesions
involving glandular crypts can be satisfactorily
Dr. W.S. Felix Wong, MRCOG, FRCS, FRCS(Ed)
treated. Blood loss during laser therapy is minimal
Senior Lecturer, O&G Dept because blood vessels less than 1 mm in diameter
The Chinese University of Hong Kong
are sealed by the laser. In contrast to cryosurgery
and electrodiathermy, laser injury to adjacent tissues
is limited to 0.3 mm and the amount of damaged
There is a significant increase in the incidence of tissue left at the end of the procedure is minimal.
cervical intraepithelial neoplasia (CIN). This These account for the reduced risk of infection and
increase is partly attributed to the increasing use of the minimal amount of vaginal discharge after laser
cervical cytological screening, and partly to the therapy. Furthermore, healing of the cervix is rapid
increased prevalence of Human Papilloma Virus and normal cervical anatomy is preserved. The new
infection. squamocolumnar junction is usually situated on the
In the past, cold knife cone biopsy or total ectocervix or at the cervical os which facilitates
hysterectomy was the recommended treatment. subsequent follow up for persistent or recurrent
However, these treatments were not ideal because disease. Cervical stenosis after laser therapy is rare2
cone biopsy carried a high complication rate and and infertility caused by laser treatment has not
hysterectomy inevitably resulted in the loss of been reported.
fertility. In the early 1970s, the revival of colposcopy
helped to exclude invasive cervical carcinoma in What is Laser?
patients with abnormal cervical smears. This made
conservative treatment, in the form of local The word LASER is an acronym for Light
destruction, applicable to the majority of patients Amplification of Stimulated Emission of Radiation.
with preinvasive cervical lesions. It was first created with synethetic ruby crystal by
Dr Teodore Maiman in 19603. Laser radiation is an
Any local destructive operation such as
cryosurgery, electrodiathermy and laser ablation can electromagnetic wave which is not mutagenic in
be curative, provided the entire CIN lesion is contrast to irradiation. Unlike ordinary light, laser
destroyed. However, electrodiathermy is painful and radiation is characterized by being coherent, highly
requires general anaesthesia. Cryosurgery can be collimated and monochromatic. Although there are
done without anaesthesia, but the result for many different kinds of laser radiation generated
advanced or extensive CIN lesions is not satisfactory, from different laser media, CO2 laser is most
and the profuse vaginal discharge afterwards makes commonly used by gynaecologists. CO2 laser
this treatment less acceptable to patients. Laser radiation is an invisible infrared light. In clinical
therapy is therefore increasingly being used for practice, the CO2 laser beam is used together with
treating CIN lesion because it confers a number of a red colour Helium-Neon laser beam to facilitate
advantages. aiming. When CO2 laser radiation is applied to the
tissue, it is selectively absorbed by the extracellular
Laser therapy is an outpatient procedure and and intracellular water. The water temperature is
requires no general anaesthesia; only 1% of patients therefore raised, the degree of which depends on
find laser therapy intolerable after local anaesthesia1. the duration of exposure and the power density of
The operation takes about 10 to 15 minutes which the laser beam. The latter is in turn controlled by
is acceptable to most patients. adjusting the power output (voltage) and the spot
The Laser is mounted on a colposcope during the size of the laser beam. A CO2 laser beam of
procedure and the laser beam is directed by a sufficient power density can raise the tissue water
Vol. 11 No. 9 September 1989
temperature to 100°C. The steam thus formed complications than a small cone biopsy, therefore a
expands explosively and vaporizes cellular and combination of laser excisional biopsy and laser
nuclear substances. This allows laser radiation to be varporization is preferrable6.
used for cutting or for tissue vaporization. When the
power density of the laser beam falls below 150
watt/cm2, the laser radiation heats up the tissue
instead of vaporizes it. This promotes blood Normal daily activities can be carried out the day
coagulation but tissue damage and necrosis also after laser therapy but patients are advised to report
results. to doctors if they develop severe abdominal pain or
fever. Vaginal spotting for the first few days after
laser therapy is to be expected. Small amount of
Laser Therapy brownish or blood stained vaginal discharge lasting
up to a month is not unusual. The next menstrual
There are 3 different forms of laser therapy. They
period may be missed, abnormally prolonged, or
are vaporization, excisional biopsy and a
heavy, but this is transient and need not. cause
combination of the two.
undue anxiety. Patients are advised against sexual
Laser vaporization is technically simple compared intercourse, use of vaginal tampon or vaginal
with the other two. It is indicated for patients with douching in the first 4 weeks after laser therapy
CIN lesion with no suspicion of invasive carcinoma. because the newly regenerated cervical epithelium
The area of vaporization includes the entire may be traumatised and infection introduced to the
transformation zone and the surrounding tissue up cervical wound. Although some gynaecologists
to 3 mm. The depth of tissue vaporization is set to prescribe triple sulphonamide vaginal cream in acid
7 mm because 99.8% of CIN lesion do not extend base for the first 8 nights after laser therapy to
into cervical glandular crypts for more than 4 mm4. prevent sepsis1, many do not think that it is
necessary. Use of other vaginal cream is otherwise
Laser excisional biopsy (laser conization) is contraindicated.
technically not difficult in trained and experienced
hands. The operation can be performed under local Postoperative management plan is carefully
anaesthesia and finished in 10-15 minutes. The explained to the patient to achieve compliance for
complication rate is similar to that of laser follow up.
vaporization but is considerably less compared to
that of cold knife conization5. It involves the use of Follow Up
high power density laser beam to excise a piece of
The first follow up examination consisting of
cylindrical or conical tissue around the cervical os
colposcopy and cervical smear is performed 4
The width and length of the specimen is governed
months after laser therapy. Because the new
by the size and site of the CIN lesion. The
squamo-columnar junction is usually visible under
advantage of laser excisional biopsy over laser
colposcopy, and persistent CIN leisons can be
vaporation is that pathological examination of the
detected and treated easily. Patients with normal
excised cervical tissue can be made. This allows
cervix are examined with cervical smears and
early detection of incomplete removal of CIN lesion
colposcopy every 4 months for another two times in
and any inadvertently missed invasive carcinoma.
the specialty clinic. Any persistent CIN lesion due to
Laser excisional biopsy of tissue around the inadequate tissue destruction is likely to be detected
cervical os coupled with laser vaporization of the in these three visits. After the first year, the chance
remaining CIN lesions on the ectocervix is indicated of detecting CIN lesion is reduced7. However these
when the CIN lesion involves large portion of the patients are still at higher risk of developing CIN or
ectocervix and invasive carcinoma in the invasive carcinoma of cervix than those without a
endocervical canal cannot be excluded. The other history of CIN, therefore a yearly cervical smear
alternative is to perform a large cone biopsy using screening test is necessary. Any CIN leisons detected
laser beam or cold knife. However, a large cone during follow up can be treated again with laser
biopsy has more immediate and long term therapy.
Carbon Dioxide Laser
Results of Treatment this, it may not be cost effective to set up a laser
therapy unit unless the volume of work is sufficient.
Cure rate for CIN after laser therapy was not
satisfactory in earlier studies8,9. In these early
attempts tissue destruction was confined only to Conclusion
areas involved by CIN leisons and the depth of
destruction was inadequate. CIN can be effectively treated by laser therapy.
Advantages of laser therapy include precise control
Recent studies report a much better result because of tissue destruction, not requiring general
adequate extent and depth of tissue destruction were anaesthesia, good patient acceptance, high
achieved during laser therapy. The overall cure rate effectiveness, low complication rate and preservation
of CIN after one laser treatment approaches 90% of cervical anatomy and function. However, proper
and this can be increased to 95% or more if the training prior to its use must be emphasized in
patient is treated more than once10,11. These results order to avoid inadvertent injuries to patients and
are not significantly different from those after attending personnels.
electrodiathermy12,13 or cryosurgery14'15'16. However,
in patients with high grade CIN lesions11'17, lesions
larger than 3 cm or extending into the endocervical Acknowledgement
canal, laser therapy has a higher cure rate than
We would like to thank Professor Allan Chang
for his constructive advice on the manuscript.
Problems with Laser Therapy
Although operative and postoperative complication
1. Anderson M C: Treatment of Cervical IntraepithelialNeoplasiawithCarbon
of laser therapy is low compared with cold knife Dioxide Laser: Report of 543 Patients. Obstet Gynecol. 1982; 59: 720-725
conization, about 1 to 2% of patients still develop 2. Baggish M S: A Comparison Between Laser Excisional Conization and Laser
Vaporization for the Treatment of Cervical Intraepithelial Neoplasia. Am J
significant postoperative haemorrhage requiring Obstet Gynecol. 1986; 155:39-44
3. Maiman T: Stimulated Optical Radiation in Ruby Masers. Nature. 1960;
admission to hospitals1. In rare occasions, surgical 187:493-494
suturing under general anaesthesia may be required 4. Anderson M C, Hartley R B: Cervical Crypt Involvement by Intraepithelial
Neoplasia. Obstet Gynecol. 1980; 55:546-550
to controll the bleeding if other measures such as 5. Larsson G, Gullberg B, Grundsell H: A Comparison of Complications of
Laser and Cold Knife Conication. Obstet Gynecol. 1983; 62:213-217
packing, reapplication of laser therapy, cryosurgery, 6. Baggish M S, Dorsey J H: Carbon Dioxide Laser for Combination Excisional-
local application of Monsel solution fail. Minor Vaporization Conication. Am J Obstet Gynecol. 1985; 151:23-27
7. Jordan I A, Woodman C B, Mylotte M J, Emens J M, William D R,
degree of vaginal bleeding occurring in the first 2 MacAlary M, Wade-Evans T: The Treatment of Cervical Intraepithelial
Neoplasia by Laser Vaporization. Br J Obstet Gynecol. 1985; 92:394-398
weeks after laser therapy is common. This contrasts 8. Burke L, Covell L C, Antonioli D: CO2 Laser Therapy of CIN, Factors
with no bleeding complication after cryosurgery. 9.
Determining Success Rates. Laser Surg Med. 1980; 1:113-122.
Baggish M: High Power Density Carbon Dioxide Laser Therapy for Early
Cervical Neoplasia. Arc Jo Obstet Gynecol. 1980; 136:117-125.
Use of laser without training can be dangerous. 10. Evans A S, Monaghan J M: The Treatment of Cervical Intraepithelial
Neoplasia Using the Carbon Dioxide Laser. Br J Obstet Gynecol. 1983; 90:553-
This may leads to inadequate treatment and results 556.
in low cure rate. Misdirected or reflected laser beam 11. Kirwan P H, Smith I R, Naftalin N J: A Study of Cryosurgery and the CO2
Laser in Treatment of Carcinoma in Situ (CIN III) of the Ulerine Cervix.
may injure normal tissue of patients or attending Gynecol Oncol, 1985; 22:195-200.
12. Chanen W, Rome R M: Electrocoagulation Diathermy for Cervical Dysplasia
personnel. The laser beam can also ignite and Carcinoma in Situ. A15 Year Survey. Obstet Gynecol. 1983; 61:673-679.
inflammable antiseptics or drapings. The mal-odour 13. Giles J A, Walker P G, Chalk P A F: Treatment of Cervical Intraepithelial
Neoplasia (CIN) by Radical Electrocogulation Diathermy: 5 Years'
fume produced during laser therapy may be Experience. Br J Obstet Gynecol. 1987; 94:1089-1093.
14. Ferenczy A: Comparison of Cryo-and Carbon Dioxide Laser Therapy for
perceived by the patient and obscure the operative Cervical Intraepithelial Neoplasia. Obstet Gynecol. 1985; 66:793-798.
field unless it is effectively evacuated by strong 15. Benedet J L, Miller D M, Nickerson K G, Anderson G H: The Results of
Cryosurgical Treatment of Cervical Intraepothelial Neoplasia at One, Five and
suction. Ten Years. Am J Obstet Gynecol. 1987; 157:268-273.
16. Townsend D E, Richart R M: Cryotherapy and Carbon Dioxide Laser
Management of Cervical Intraepithelial Neoplasia. A Controlled Comparison.
Installation, maintenance and running cost of Obstet Gynecol 1983; 61:75-78.
laser machines are more expensive compared with 17. Wright V C, Davies E M: The Conservative Management of Cervical
Intraepithelial Neoplasia. The Use of Cryosurgery and the Carbon Dioxide
other instruments used to treat CIN. Because of Laser. Br J Obstet Gynecol 1981; 88:663-668.