METHODS

A single centre, prospective, non-comparative, interventional case series of 27 eyes in 26 patients with primary OSSN was carried out between November 1998 and February 2003.

Inclusion criteria included histologically confirmed non-invasive limbal OSSN (with associated corneal involvement) of less than 4 clock hours in extent. All treatment was carried out by a single ocular oncologist (JM). All of the lesions were completely excised superficially from the cornea and limbus with a 2 mm margin on the conjunctival aspect. Lamellar dissection was not performed as this increases the risk of intraocular spread if invasive disease. Double freeze-thaw cryotherapy with a nitrous oxide cryoprobe was applied to the superificial limbal base and to the full thickness of the elevated conjunctival edge. Cryotherapy was not available in all centres where the treatment was undertaken and therefore not used in all cases. Patients were treated with chloramphenicol and Prednefrine Forte eye drops four times daily until wound healing.

All cases were treated with at least two 1 week courses of topical MMC 0.04% four times a day, after complete epithelial healing.⁶ Each course was followed by 1 week free of MMC. The patients were examined at 6 monthly intervals. The primary outcome measure was clinical recurrence of OSSN.

RESULTS

There were 26 patients, seven females and 19 males, with 27 primary OSSN (table 1). The mean age was 64 (SD 13) (range 47–87) years.

Five patients developed granuloma following excision of OSSN, all of which resolved rapidly with continued topical steroid treatment. Nineteen patients received three courses of MMC. Eight patients received two courses because of allergy to MMC with redness, swelling, and significant itching, which developed late in the second course. All MMC allergy symptoms resolved rapidly following discontinuation of treatment.

All patients have been followed up. The mean follow up period for the 26 patients was 27 (SD 12) months (range 12–50 months, median 25 months). There was no evidence of clinical recurrence in any of these cases.

DISCUSSION

Ocular squamous surface neoplasia (OSSN) is characterised by a localised, slow growing lesion with low metastatic potential. Histopathologically, there is a spectrum of intraepithelial change before the basement membrane is breached and invasive squamous cell carcinoma results.^1,2

Our study represents the largest series to date of primary OSSN treated with adjunctive topical MMC. The authors believe MMC treatment following surgical excision is effective for local control as attested by the zero recurrence rate at a mean of 27 months.

Primary excision has been the mainstay of treatment for OSSN.⁵ The authors feel that superficial excision remains the important initial step in management as it is impossible to exclude invasive disease on clinical grounds or with impression cytology. Excision allows an immediate histopathological diagnosis, surgical debulking, and excludes life threatening invasive carcinoma.⁷ The disadvantage of primary excision alone is the high recurrence rate which ranges from 15% to 52%.⁸ Therefore, numerous adjunctive treatments have been described in an attempt to decrease the rate of recurrence and the efficacy of various adjunctive therapy have been debated.

Intraoperative cryotherapy is commonly used as adjunctive therapy as it is known to decrease the recurrence rate by destruction of any residual tumour tissue beyond the horizontal or deep surgical margin of the wound.⁸ In this study, there is no difference in the overall recurrence rate in those who received cryotherapy compared with those who did not. Further randomised controlled trials comparing excision with MMC versus excision, MMC, and cryotherapy will help determine the efficacy of cryotherapy in conjunction with MMC.

Mitomycin C is an alkylating agent which acts by inhibiting DNA synthesis and produces cell death by apoptosis and necrosis.⁹ The drug has a preferential action for rapidly dividing cells and has significant anti-tumour activity. Since 1994 several groups have reported the use of MMC in the treatment of both primary and recurrent OSSN.^10–16 We think that it is unwise to use MMC without excision biopsy for localised OSSN, as invasive disease may be undiagnosed and MMC is unlikely to penetrate to the required level to reach the invasive cells.

MMC allows treatment of the entire ocular surface, including the conjunctival fornices, and may reach and destroy subclinical disease and prevent new tumours arising elsewhere on the ocular surface. Complications of MMC are common but are largely confined to ocular surface toxicity. The largest problem with MMC in our series was local allergy necessitating termination of treatment, as seen in eight cases (30%). None of our patients experienced significant corneal epitheliopathy and this may be attributed to the week on, week off regimen which prevents damage to more slowly dividing epithelial cells and limbal stem cells, allowing them to repair their DNA. We believe that allowing time for complete epithelial healing before application of MMC is important in avoiding the more serious complications such as scleral ulceration, uveitis, cataract, and glaucoma.^4,10,14 We noted no systemic side effects as a result of topical MMC treatment.

In conclusion, our study demonstrates that MMC treatment following surgical excision decreases recurrence rate of primary ocular surface neoplasia and should be considered as an adjunctive therapy in primary excision. As there was no difference in recurrence rate with two courses of MMC, the authors intend to use only two courses in the future.