CHAPTER 138 Cryotherapy of the Cervix
Cryotherapy is the treatment of choice for select small cervical intraepithelial lesions (cervical intraepithelial neoplasia [CIN] 1, 2, and 3, or mild, moderate, and severe dysplasia). This procedure is easy to learn, is well tolerated by the patient, and has a success rate similar to other therapies, including LEEP (the large loop electrical excision procedure) and laser. It requires a refrigerant gas under pressure, such as nitrous oxide, and an applicator probe. The cryoprobe allows rapid freezing of cervical tissue, causing a controlled destruction of the transformation zone and the epithelial lesion. Cellular destruction is greatest when a rapid freeze, slow thaw, and refreeze method is used. This efficacious procedure has few complications, can be performed quickly, is low in cost, and preserves cervical tissue.
The only negative aspect is that there is no tissue specimen available to confirm removal of all abnormalities. However, considering that up to 18% of patients experience pregnancy complications after LEEP, cryotherapy should be strongly considered for women who meet the criteria for treatment.
Cryotherapy treats cervical dysplasia by destroying the lesion and the transformation zone. Cell death occurs as a result of ice crystal penetration into the intracellular space. The depth of destruction is directly proportional to the lateral spread of the freeze, which is measured by the size of the ice ball that forms around the tip of the cryoprobe. An ice ball of 5 to 7 mm will result in adequate cellular destruction, because severe dysplasia (CIN 3) can extend to a depth of 3 to 5 mm into the glands in the transformation zone. The frequency and depth of gland involvement seem to be directly proportional to the grade of the squamous intraepithelial lesion. However, the overall success of cryotherapy is related more to the size of the lesion than the grade of the lesion. Small high-grade lesions (<1 cm) may be adequately treated with cryotherapy. Low-grade lesions should be less than 3 cm in diameter (some recommend <2 cm). For all lesions, they should involve no more than two quadrants of the cervix and extend no more than 5 mm into the endocervical canal. Large high-grade lesions (>1 cm), microinvasive lesions, and invasive lesions need more aggressive treatment such as LEEP, conization, or even hysterectomy.
Treatment failures may occur with cryotherapy as with any other treatment modality. “Cure rates” have been in the 95% range for CIN 1 and CIN 2, which is consistent with other modalities. For CIN 3 the cure rate drops to 89% overall, but this has been correlated more to lesion size and depth, not to severity of disease. High-grade lesions are often larger and extend deeper into the glands, making them more difficult to treat.
Cryotherapy may be used for treatment of squamous dysplasia that was confirmed with a biopsy after a complete and adequate colposcopic examination and if all criteria noted later have been met. It is essential that the Pap smear results, the appearance of the cervix on colposcopic examination, and the histologic report from the biopsy do not vary by more than one degree of severity. That is, colposcopic impression and histologic findings can only be one degree less severe than the Pap smear findings. If there is lack of correlation, this must be resolved or a LEEP or conization of the cervix is indicated because it is presumed the most advanced lesion has not been identified. It is common for histology to be worse than the Pap smear because the Pap smear is a screening test only. However, the Pap smear is essentially never two grades worse than tissue pathology or biopsy. If the correlation principle is met, the patient would then be treated based on biopsy findings. Cryotherapy may be used to treat low-grade squamous intraepithelial lesions (LSILs) and small, focal high-grade intraepithelial lesions (HSILs). Large high-grade lesions usually have deeper gland involvement, and these patients will need to have an excisional treatment, such as LEEP or conization. Cryotherapy is not appropriate for any invasive lesion. The practitioner must be sure to differentiate between “carcinoma in situ” and “microinvasive cancer.” Although select patients with carcinoma in situ who meet the criteria may be treated with cryotherapy, microinvasive lesions should never be treated this way. Patients with microinvasive disease need a conization procedure to determine the true extent of the disease.
Cryotherapy may also be useful to treat patients with chronic cervicitis that is culture negative and unresponsive to antibiotic therapy, and has negative colposcopy and biopsy findings. External genital human papillomavirus lesions may be treated with cryotherapy, although a different freezing technique is used (see Chapter 14, Cryosurgery, and Chapter 155, Treatment of Noncervical Condylomata Acuminata).
Many would suggest that all CIN III lesions (i.e., carcinoma in situ) be treated with conization procedures. However, the data strongly support the efficacy of properly performed cryotherapy for small lesions that meet the aforementioned criteria. Cryotherapy is much more cost effective, with potentially fewer and less significant complications.