Comparison of depth of necrosis using cryotherapy by gas and number of freeze cycles

J Low Genit Tract Dis. 2015 Jan;19(1):1-6. doi: 10.1097/LGT.0000000000000042.


Objective: This study aimed to establish the noninferiority of a single-freeze application with CO2 or N2O compared with the standard double freeze with N2O for cryotherapy treatment.

Materials and methods: Sixty women undergoing hysterectomy for reasons other than cervical cancer or precancer were randomized to 1 of 3 techniques as follows: (1) double freeze with N2O, (2) single freeze with N2O, or (3) single freeze with CO2. The cervix was separated and cut into anterior and posterior segments, and the deepest area of necrosis was recorded. Comparisons were made using regression analysis. The margin of noninferiority was defined as 0.8 mm.

Results: On the anterior lip, a single freeze with N2O was noninferior to a double freeze of the same gas, but on the posterior lip, the single freeze was not. The single freeze of CO2 did not provide sufficient depth of necrosis in either lip to infer noninferiority versus the double freeze with N2O.

Conclusions: A single freeze with N2O is noninferior to a double-freeze technique in the anterior but not the posterior lip. However, the result for posterior lips was close to reaching statistical significance. In addition, CO2 had approximately 1 mm shallower depth of necrosis compared with N2O techniques; however, the clinical implications are unknown. Given the extensive use of CO2 globally, further clinical evaluation is needed.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Carbon Dioxide / therapeutic use
  • Cervix Uteri / radiation effects*
  • Cryotherapy / methods*
  • Female
  • Gases / therapeutic use*
  • Humans
  • Middle Aged
  • Necrosis*
  • Nitrous Oxide / therapeutic use


  • Gases
  • Carbon Dioxide
  • Nitrous Oxide