A Comparison of Flat and Shallow Conical Tips for Cervical Cryotherapy

Abstract

J Am Board Fam Pract 1999;12:360–6 Both flat and shallow cone-shaped cryoprobe tips are used for cryotherapy of the cervix. Some controversy exists regarding which is more effective in eradicating CIN and more likely to cause the posttreatment squamocolumnar junction (SCJ) to be positioned within the endocervical canal. These two outcomes were assessed after 84 women returned for post-therapy evaluation following nitrous oxide cryotherapy using a flat or cone-shaped probe tip. Cure rates for CIN were equivalent, 76% and 77%, for the flat and cone-shaped tips, respectively. All posttreatment colposcopy exams were considered satisfactory. The flat tip was more apt to prevent posttreatment SCJ positioning within the endocervical canal when compared with the cone-shaped tip only when the pretreatment SCJ was located entirely on the ectocervix (p = .04). Editorial Comment: It is no surprise that the cone-shaped tip was more likely to force the posttreatment SCJ into the endocervical canal. Furthermore, since all posttreatment colposcopy exams were considered satisfactory, the tendency for more proximal SCJ positioning should not be considered clinically significant. Observation of the posttreatment location of the SCJ on the ectocervix or at the os helps to assess cure clinically, but a cytologic sampling of the endocervical canal is mandatory to evaluate outcome. Regardless, effective treatment always takes precedence over the location of the SCJ. Maximal tissue/probe contact is preferred to ablate the majority of CIN lesions that are located within the central or inner curve area of the cervix. Because the cone-shaped tip conforms better to the epithelium and extends further towards the os, more effective ablation occurs. Other researchers have documented that the cone-shaped probe is better able to destroy neoplastic epithelium. However, the assumption that both tips are equally effective in eradicating CIN should not be considered proven by this study. The sample was extremely small and of insufficient size to detect a clinically significant difference in outcomes. The abbreviated follow-up interval may have also influenced these data. Finally, the cryotherapy technique used was very likely inadequate based on the facts that rather poorer than average cure rates were reported, large cervical lesions greater than two quadrants in size not typically conducive to cryotherapy were treated, and no single postcryotherapy colposcopy examination was considered unsatisfactory (an extremely unlikely probability if effective cryotherapy is implemented). Therefore, cone-shaped probe tips are indicated for treating centrally positioned lesions and the transformation zone, and flat-tips are used when overlapping treatment beyond the central area is necessary. (DGF)