Carbon dioxide (CO2) and Neodymium: yttrium aluminium garnet (Nd:YAG) lasers have been used as first-line therapy with reasonable response rates and good cosmetic and functional results. The CO2 laser is typically used at a power setting between 15 and 20 W, and has a penetration of 2-2.5 mm. Direct focusing of the beam allows it to be used as a scalpel to excise tissue for histological analysis. Ablation sites generally heal in 3-4 weeks. The Nd:YAG laser is typically used with the power set between 24 and 60 W. It has a tissue penetration of 4-6 mm, but causes tissue coagulation and therefore prevents histological diagnosis and a risk of understaging the disease. Larger lesions can be treated using this laser, but ablation sites can take up to 2-3 months to heal (Fig. 5.11). Treatment with either of these lasers is usually well tolerated, with minor complications ranging from minor pain and bleeding at treatment sites, to preputial lymphoedema in those patients who have retained their foreskin.69
In one study, van Bezooijen et al. reported their experience of 19 Tis patients treated with laser therapy. After a mean follow-up of 32 months, 26% required successful retreatment for histologically confirmed Tis recurrence, while one patient (5%) progressed to invasive disease, highlighting the importance of close follow-up after such minimally invasive surgery.70 In a more recent study assessing the combined use of both lasers, 13/67 (19%) patients had disease recurrence, with upgrading from the original tumor in 3/13 (23%) cases.2 1 Higher recurrence rates after laser treatment may reflect a tendency to tackle larger tumors with this minimally invasive approach compared to those treated by other topical therapies. Lasers have been used to treat lesions up to stage T2, but this approach has been shown to be associated with higher overall recurrence (48%), and evidence of nodal progression in 23%,72 highlighting the need for careful case selection.
Laser therapy is primarily used to treat PIN and BP, and is not suitable for LS, large GCA, or cutaneous horn.
Cryotherapy has been used for a multitude of skin lesions by dermatologists for some time. The technique of using either liquid nitrogen or nitrous oxide to generate rapid freeze/ slow thaw cycles, can achieve tissue damage at temperatures below -20°C, although temperatures of -50°C are required to effectively kill malignant cells. Tissue damage occurs by formation of intracellular and extracellular ice crystals, leading to disruption of cell membranes and cell death. While there is little comparative data on the use of this modality for penile lesions, a large study of 299 patients comparing cryotherapy to topical chemotherapy with 5-FU and surgical excision for Bowen's disease affecting both men and women, primarily in extragenital locations, showed cryotherapy to have a greater risk of recurrence (13.4%) when compared to 5-FU (9%) and surgical excision (5.5%) after 5 years follow-up.73
Photodynamic therapy (PDT) for penile PIN is still in its infancy. This technique involves covering the affected region with a topical photosensitizing cream
Fig. 5.11 Appearance of the penis in a 49-year-old smoker who had undergone circumcision for grade 3 SCC Stage T1 of the foreskin 3 years previously and CO2 laser treatment of SCC Stage Tis of the glans penis 9 months previously at another institution. Frontal views of the penis (a) before and (b) after 5% acetic acid preparation show enhancement of the lesions: SCC Stage Tis and PENIN involving left side (arrows) and SCC Stage T1 involving ventral glans (arrows). Same views (c) immediately after KTP/532 laser treatment and (d) 2 months postoperatively (Reprinted from Tietjen and Malek,69 Copyright 1998, with permission from Elsevier)
containing chemicals such as delta-5-aminolaevulinic acid (ALA) for approximately 3 hours. Such chemicals are preferentially taken up and retained by malignant cells. The area is then treated by illumination of an incoherent light from a specialist PDT lamp leading to photoselective cell death of sensitized cells. One study looking at ten patients treated with PDT found an initial response in 7/10 patients.74 4/10 had a complete response after a mean follow-up of 35 months, but required between 2 and 8 treatments (mean of 4 treatments). 3/10 patients had persistent recurrence refractory to PDT, although none of these patients progressed to invasive disease. Further trials on this technology are awaited.
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