The CO2 laser utilizes focused infrared light energy. This energy is absorbed by the tissues, making the tissue water to vaporize. The target area gets void of water, is not viable any longer, so the lesion gets destroyed. Laser allows precise tissue ablation by spatial limitation of thermal damage and effective vaporization.

CO2 laser therapy is a useful treatment method, especially for extensive warts and can be used at difficult anatomical sites. It is typically performed in an office. In some particular cases (large lesions, pediatric patients) anesthesia may be required and therefore this procedure should be done in hospital under general anesthesia. The CO2 laser is very precise and therefore it spares normal tissue, probably it eliminates the infective agent and also has a good cosmetic effect. However, it is considerably more expensive than other destructive methods used for GW treatment (cryotherapy, electrosurgery or surgical excision).

In most of the cases, healing is rapid. The risk of scaring is small but is greater than of cryotherapy. Other side effects are similar to those of surgery. It has been shown that the plume of smoke resulting form laser technique may contain papilloma virus DNA, with contagious potential for operating personnel (infection of the respiratory tract). However, if appropriate equipment is used, the risk for contamination is basically null (Garden JM, 1988; Scheinfeld NS, 2005; Weynandt GH, 2011).
Efficacy and Recurrence
Overall, the clinical studies have shown clearance rates between 23% and 52%, whereas the recurrence rates varied from 60% to 77% over a follow-up period of 3-18 months (International Collaborative Study Group, 1993; Duus BR, 1985; Reid R, 1992; Petersen C, 1991).

A study comprising 208 patients (135 women and 73 men) with vaginal and external anogenital warts was designed to compare the outcomes of electrosurgery and laser therapy. To avoid selection bias, in each patient half of the lesions measuring 2 cm2 or greater total linear area were treated with electrosurgery, and the other half were treated with laser excision. The follow-up was at least 6 months after the last treatment received. Clearance was achieved in 95% of patients with a lesional area of 5 cm2 or less, and 100% of patients with 5 cm2 or larger by the third and sixth postoperative week, respectively. Similar side effects occurred in both groups: severe discomfort (12% of patients), and delayed complications, including vitiligo and scarring (4% of patients). Complete clearance of warts after a single session (51% vs 38%) and multiple treatments (75% vs 64%) were similar for electrosurgery and CO2 laser. In vaginal and external GW electrosurgery and continuous wave CO2 laser seems to be equally effective especially if the lesions are limited to a 5 cm2 or less area (Ferenczy A, 1995).

Another randomized trial in patients with refractory GW also found the carbon dioxide laser did not offer any advantages over traditional surgery, including electrocautery (Duus BR, 1985). No difference between the two treatments was seen in numbers of recurrences, postoperative pain, healing time, and rate of scar formation.
One-hundred-six patients treated with CO2 laser for GW were followed for 6 months. At one month follow-up, clearance was found in 81.2% of cases, recurrence in 12.6% and persistence in 6.6%. Ninety-three percent of patients in remission at one month were still in remission at three months. At six months, 83% of patients were in remission after 1.4 laser treatments. (Aynaud O, 2008).

A case-control study was performed on pregnant women with GW treated with CO2 laser. Two-hundred-eighty women received treatment during pregnancy and 256 women were treated three months after delivery. Recurrence rates over a 2 year follow-up were higher in the women treated in postpartum (p < .01) than in the group treated during gestation (p < .005). Clinical HPV infections treated during the second trimester of pregnancy were associated with a decrease in recurrence rate of infection (Frega A, 2006). Another study evaluated the complication rate and patient satisfaction in male patients with extensive GW treated with laser or electrosurgery. Questionnaires were used retrospectively in 64 consecutive men (answer rate 60% or 64/107 addressed persons). The mean follow-up was 25 months (range 7-75). The overall clearance rate after 1 session of treatment was 67%. The clearance and recurrence rates were similar for both HIV-positive and HIV-negative groups. However, the cure rate was influenced by localization: endoanal versus perianal: 56 versus 84% (odds ratio = 4.06; p = 0.03). After a second treatment session, the cure rate increased to 79% or higher in all subgroups. Painful defecation for an average of 4-5 weeks was the main postoperative complaint. (Carroza PM, 2002). It appears that administration of interferon alpha-2b subcutaneously following laser therapy in patients with resistant GW is beneficial. Interferon was fairly well tolerated in a trial and significantly improved the clearance rates: 14/27 patients (52%) cured in the group treated with laser plus interferon, vs 5/22 (23%) patients in laser plus placebo group (Petersen CS, 1991). In conclusion, laser surgery is as effective as surgical excision at clearing and preventing recurrence of genital warts. Even it was considered at one time the method of choice for treating GW, it has not be proven to be superior to other therapy options. References Aynaud O, Buffet M, Roman P, Plantier F, Dupin N. Study of persistence and recurrence rates in 106 patients with condyloma and intraepithelial neoplasia after CO2 laser treatment. Eur J Dermatol. 2008 Mar-Apr;18(2):153-8. Condylomata International Collaborative Study Group. Randomized placebo-controlled double-blind combined therapy with laser surgery and systemic interferon-alpha 2a in the treatment of anogenital condylomata acuminatum. J Infect Dis 1993;167:824-9. Duus BR, Philipsen T, Christensen JD, Lundvall F, Søndergaard J. Refractory condylomata acuminata: a controlled clinical trial of carbon dioxide laser versus conventional surgical treatment. Genitourin Med. 1985 Feb;61(1):59-61. Frega A, Baiocco E, Pace S, Palazzo A, Iacovelli R, Biamontil A, Moscarini M, Stentella P. Regression rate of clinical HPV infection of the lower genital tract during pregnancy after laser CO2 surgery. Clin Exp Obstet Gynecol. 2006;33(2):93-5. Garden JM, O'Banion MK, Shelnitz LS, Pinski KS, Bakus AD, Reichmann ME, Sundberg JP.: Papillomavirus in the vapor of carbon dioxide laser-treated verrucae. JAMA. 1988;259:1199-202.

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