Ablative and excisional treatments constitute two forms of out-patient surgical treatment of cervical intraepithelial neoplasia (CIN). Cryotherapy, electrocoagulation, cold coagulation and laser ablation are different methods of ablative treatment of CIN. The loop electrosurgical excision procedure (LEEP), using thin wire loop electrodes and long needle electrode electro-surgical cylindrical excision are the major forms of out-patient excisional treatment of CIN.
Of all available and effective treatments of CIN, cryotherapy and LEEP are appropriate for both high- and low-resource settings for several reasons and, hence, only these two methods are discussed in this field manual. First, they require the least financial investment for equipment, maintenance and repair. Second, once colposcopy has been mastered, cryotherapy and LEEP can be quickly learned and result in high cure rates and few complications. Other surgical techniques that are based on the laser or electrocoagulation are beyond the scope of this manual and the learner is referred to excellent books that have been written on their use ( Wright et al., 1992
; Wright et al., 19.5
; Singer & Monaghan, 2000
The primary concern in treating CIN by ablative (destructive) or excisional techniques is whether the treatment will be adequate to eradicate any CIN that has extended down into the crypts underlying the neoplastic epithelium. The possible depth of crypt involvement increases with the severity of the CIN. A treatment that is effective to a depth of 7 mm is necessary to destroy CIN 3. The total linear extent of the lesion is also a factor to be considered. The linear extent of a lesion is the sum of its two distances, each measured from a reference point at the external os: the distance to the proximal edge (towards or into the canal) and the distance to the distal edge of the lesion (away from the canal). The average linear extent is 7.5 mm (range 2 to 22 mm) with 85 to 90% of lesions entirely visible externally on the transformation zone ( Wright et al., 19.5
). Vaginal extension is present in no more than 5% of patients.
The principles and practice of cryotherapy are discussed in this chapter and LEEP is described in the next chapter
. Cryotherapy equipment (Figures 12.1
) costs substantially less to buy and to maintain than that required for LEEP. Cryotherapy does not require a source of electricity as LEEP does, but relies instead on a supply of easily transportable tanks of highly compressed refrigerant gas. After the vaginal speculum is in place and the cervix has been visualized, both procedures take approximately 15 minutes from start to finish.
Ancillary equipment is required for LEEP, but not for cryotherapy for several reasons. Although the performance of cryotherapy usually does not require a local anaesthetic, LEEP does require several injections of a local anaesthetic into the ectocervix. LEEP generates smoke that remains in the vagina unless it is evacuated by a vacuum system to allow an unobstructed view of the operative field. The third type of ancillary equipment required for LEEP is an electrically insulated vaginal speculum (and insulated vaginal side-wall retractor, if necessary) (Figure 13.3
) or a metallic speculum insulated with latex condom (Figure 4.9
) to prevent an electrical injury (shock or thermal injury) to the patient or the operator if the loop or the ball electrode accidentally touches the instrument. Since a metallic vaginal speculum conducts electricity, it may lead to an electrical injury to the vagina if the loop accidentally comes into contact with these metallic instruments. Insulated vaginal specula and insulated vaginal side-wall retractors are more expensive than non-insulated ones.
In contrast to LEEP, which is an excisional technique, cryotherapy is an ablative one. In practical terms, this means that there will be no pathology specimen to evaluate after cryotherapy which obviously has an immediate cost saving. Proponents of LEEP appreciate the feedback of information if there is a pathological examination of the LEEP excised tissue. This feedback allows a reassessment of not only the most severe grade of lesion present, but also the adequacy of excision (whether excisional margins are involved).
The main limitation of cryotherapy is that it is not adequate to treat lesions that are not wholly located on the ectocervix, yet involve the endocervical canal. In contrast, LEEP can adequately excise the majority of cervical lesions, whether or not the canal is involved. Meta-analysis of randomized clinical trials that evaluated the comparative effectiveness of cryotherapy with therapies such as LEEP, conization and laser, have concluded that the above treatments are equally effective in controlling CIN ( Nuovo et al., 2000
; Martin-Hirch et al., 2000
). From the foregoing comparisons and contrasts, it is empirically clear that the most practical and cost-effective method of treatment of CIN in low-resource settings is cryotherapy, provided the lesion is wholly ectocervical in location. LEEP is the treatment of choice if the lesion involves the endocervical canal (see Chapter 13
Since LEEP is technically more demanding than cryotherapy, we suggest that colposcopists should first demonstrate competence with cryotherapy before they perform LEEP.
If living tissue is frozen to a temperature of -20°C or lower for at least 1 minute, cryonecrosis ensues. Several features distinguish this process: intra- and extra-cellular crystallization, dehydration, thermal shock, vascular stasis and protein denaturation. A rapid freeze followed by
a slow thaw is the most damaging to cells, especially neoplastic cells. A sequence of two freeze-thaw cycles (freeze-thaw-freeze-thaw) may produce more tissue destruction than a single cycle.
The cryotherapy technique uses a cryoprobe with a tip made of highly conductive metal (usually silver and copper), that makes direct surface contact with the ectocervical lesion. A substantial drop in temperature is achieved when a compressed refrigerant gas is allowed to expand through a small aperture in the cryoprobe. Nitrous oxide (N2O) or carbon dioxide (CO2) are the refrigerants of choice, as both provide excellent thermal transfer when circulating in the probe tip.