Conjunctival tumors include a large spectrum of disease involving the ocular surface (the conjunctiva and the cornea), characterized by different biological and clinical characteristics and behavior.1 Although surgical excision remains the standard treatment modality for most conjunctival malignancy, in the past decades the introduction of topical chemotherapy has rapidly changed the therapeutic approach to these lesions.2 Topical chemotherapy has several advantages when compared with standard surgical excision, including treatment of the entire ocular surface, targeting of the tumor cells, simplicity of treatment, reduced cost associated with avoidance of the surgical approach, and reduced patient morbidity.2-4 Topical chemotherapy is actually used as an adjuvant treatment (after surgery, to reduce the risk of recurrences), as a neoadjuvant treatment (before surgery, to reduce the dimension of the tumor before its surgical excision), or as a sole treatment.2,4 Three main drugs are currently used for topical chemo- and immunotherapy of conjunctival tumors: mitomycin C (MMC), used for both pigmented [conjunctival melanoma and primary acquired melanosis (PAM)] and nonpigmented [ocular surface squamous neoplasia (OSSN)] epithelial tumors; 5-fluorouracil (5-FU), whose use is reserved for nonpigmented epithelial lesions (OSSN); interferon-α2b (IFN-α2b), used for both pigmented (conjunctival melanoma, PAM) and nonpigmented (OSSN) epithelial tumors, and also for conjunctival mucosaassociated lymphoid tissue (MALT) non-Hodgkin lymphoma.2-5
The aim of this review is to summarize the current trend in the use of topical pharmacotherapy and immunotherapy for the treatment of conjunctival tumors.
MATERIALS AND METHODS
To identify potentially relevant articles in the medical literature, we searched MEDLINE for English language articles published from January 1970 to December 15, 2016. MEDLINE was queried using the following search terms (used both individually and in combination for advanced research): pharmacotherapy, chemotherapy, immunotherapy, topical chemotherapy, local chemotherapy, mitomycin C (MMC), 5-fluorouracil (5-FU), interferon (IFN), conjunctival neoplasm, conjunctival tumor, primary acquired melanosis, conjunctival melanoma, conjunctival squamous cell carcinoma (SCC), ocular surface squamous neoplasia, conjunctival lymphoma, conjunctival mucosa-associated lymphoid tissue lymphoma, conjunctival dysplasia, and conjunctival intraepithelial neoplasia (CIN). Additional articles were identified by reviewing the references of examined publications. To identify potentially relevant articles to include in this review, 2 investigators reviewed each paper. Case series were preferred to single-case reports. Articles included in the reference list were fully examined by the authors.
TOPICAL CHEMOTHERAPY OF CONJUNCTIVAL TUMORS
Mitomycin C is an antibiotic isolated from Streptomyces caespitosus acting as an alkylating agent, affecting the cells during all phases of the cell cycle.2 Mitomycin C binds to nuclear DNA leading to irreversible cross-linking and inhibition of nucleotide synthesis. Mitomycin C seems to be toxic to both proliferating and nonproliferating cells.3 It is soluble in water and organic solvents and in aerobic conditions, as in topical application, MMC can also generate free radicals, causing direct cytotoxicity by DNA and protein damage via lipid peroxidation.2,4 Its biologic effect on conjunctival tumors is enhanced by NAD(P)H quinone oxidoreductase 1 (NQO1), a bioactivating enzyme for MMC that is present in conjunctival and corneal epithelial tumors, mainly in OSSN.3,4 Mitomycin C eyedrops need light protection and should be stored at room temperature (22°C) for up to 1 week or refrigerated (4°C) for up to 3 months with preservation of 90% of activity.4
The Use of Mitomycin C in Primary Acquired Melanosis
Several authors reported the use of MMC in melanocytic premalignant (Table 1) and malignant (Table 2) lesions of the conjunctiva, both as sole therapy or as neoadjuvant or adjuvant treatment, along with in the treatment of recurrences.6-24 The most common dose and therapeutic regimen consists of 0.04% MMC eye drops (0.4 mg/mL) used 4 times per day for 14 consecutive days (1 cycle), with or without 1 or 2 weeks of therapy-free interval between each cycle.13,14 The first case reports describing the use of topical MMC in the treatment of PAM with atypia were published in the 1990s by Frucht-Pery et al (1996, a single case),6 Finger et al (1998, 10 cases),7 and Salomao et al (1999, 10 cases).8 After these encouraging results many other case series were reported.9-25 Finger et al7,9,13 published several papers describing their clinical experience with the use of MMC for conjunctival melanocytic lesions and in 2005 reported a case series of 8 eyes affected by PAM and treated with 0.04% MMC for 2 cycles (14 days per cycle) as a sole and primary treatment.13 All patients showed a clinical regression of the lesions, but 3 patients showed a recurrence of the disease in long-term follow-up (mean, 81 months). Pe’er et al14 reported a series of 9 patients affected by PAM with atypia and treated by topical MMC as a primary treatment (14 days per cycle; range, 2 to 5 cycles; 2-week intervals) until disappearance or stabilization of the remnant pigmentation. Shields et al11 also reported the effectiveness of topical MMC (0.04%) on corneal melanosis in 1 patient, avoiding the need for surgery and its relative side effects. In 2010, Russel et al18 reported the treatment of 17 patients affected by PAM with atypia with topical MMC (0.04%). Of these, 16 patients were treated as a primary treatment, whereas a single patient as a neoadjuvant therapy. The authors reported 2 cases of lack of response and 3 recurrences during follow-up.18 Other authors reported the use of topical MMC in a lower concentration (0.02%).6,8,14,16,17 This reduced dosage was introduced to reduce MMC-related side effects. Hung et al16 reported the use of 0.02% MMC in 2 patients affected by conjunctival PAM, with no recurrences during follow-up. However, one of these patients experienced temporary drug toxicity similar to those treated by the 0.04% concentration. When using topical MMC for the treatment of PAM, in a consistent proportion of treated eyes the conjunctival pigmentation does not resolve completely after the treatment. Nevertheless, this pigment persistence is not a sign of lack of response to the therapy, as this usually represents a grouping of normal melanocytes with increased pigmentation and extracellular pigment deposition in the area of the pre-existing lesion.2,14 Moreover, the aspect of treated lesions is characterized by a progressive pigment degranulation, clinically characterized by a reorganization of the pigmentation in small clusters separated by areas of absence of pigmentation (Fig. 1). Regular observation appeared adequate to evaluate eventual progression of the pigmentation and the necessity of retreatment in these cases.14
The Use of Mitomycin C in Conjunctival Melanoma
Finger et al20 first reported a single case of recurrent conjunctival melanoma treated with topical MMC as a neoadjuvant treatment, obtaining a decrease of the pigmentation and thinning of the nodular part of the lesion. Kurli et al13 reported early tumor recurrence in 2 patients (100%) affected by conjunctival melanoma and treated with 2 cycles of 0.04% MMC as a primary treatment. The other 6 patients were treated using a reduced cycle of MMC (7 days), used as adjuvant therapy after surgical tumor removal starting within 2 weeks of the surgery. Three of these patients (2 treated with MMC as a primary treatment and a single patient as an adjuvant treatment) developed orbital recurrences requiring orbital exenteration.13
Successful primary treatment with 0.04% MMC was obtained in conjunctival melanoma by Pe’er et al14 in 2 of the 3 reported cases. Nevertheless, these authors emphasized that these patients presented with only minor extensions of PAM that minimally broke through the basement membrane. In another series described by Ditta et al,23 including 15 eyes affected by conjunctival melanoma and treated with a 3-week cycle of 0.04% MMC after surgery, 5 patients developed recurrences after a median of 19 months. These authors also described a correlation between tumor recurrences and a delay in starting the topical therapy. Metastatic disease was subsequently diagnosed in 3 patients, with 2 of them needing orbital exenteration because of concurrent orbital recurrence.23 The largest series of conjunctival melanoma treated by topical MMC was reported in 2010 by Russel et al,18 including 22 consecutive eyes. Among them, 4 patients were treated as a primary treatment, 4 as neoadjuvant treatment, and 14 for adjuvant purposes. The authors reported a single case of complete lack of response and 5 recurrences during follow-up.
The Use of Mitomycin C in Conjunctival Intraepithelial Neoplasia
Several authors reported the use of MMC in the treatment of noninvasive (Table 3) and invasive (Table 4) OSSN.3,10,15,18,26-47 The first paper describing the use of topical MMC in the treatment of patients affected by CIN was published in 1994 by Frucht-Pery et al.26 These authors obtained complete tumor control in all 3 enrolled cases using topical MMC 0.02%. After this first report, the same group published several papers describing the efficacy of both 0.02% and 0.04% MMC, used 4 times daily for 2 consecutive weeks in noninvasive OSSN.29,31 Mitomycin C (0.04%) was also used by Wilson et al28 in a short case series of 7 patients with diffuse CIN, who were considered poor surgical candidates or who had experienced recurrences despite prior surgical treatment. A single patient required subsequent surgical excision and adjunctive cryotherapy for a partial response. Gupta et al,43 in 2010, reported a case series of 81 patients affected by localized noninvasive CIN (73 cases) or recurrent CIN (8 cases). These patients were treated with surgical excision and cryotherapy, followed by 2 to 3 1-week cycles of adjuvant topical MMC (0.04%). Another 10 patients affected by diffuse CIN were also included, receiving 2 to 3 1-week cycles of topical MMC (0.04%) as sole and primary treatment. After a mean follow-up of 56.8 months (range, 5.8 to 119.8) no recurrences were documented in the group of localized tumors treated with MMC as a sole and primary therapy. A single case of tumor persistence and 2 recurrences were reported in the group of diffuse tumors treated with MMC as a sole and primary therapy. A single recurrence was also documented in the group of recurrent tumors.43 Bahrami et al,46 comparing MMC and 5-FU in the adjuvant treatment of noninvasive and localized OSSN, reported no recurrence in 64 eyes treated with 0.04% MMC applied 4 times a day on a week-on week-off basis for 2 to 3 cycles. Rudkin et al47 in a larger series (28 patients) of diffuse pre-invasive lesions (defined as extended over 5 or more clock hours of limbus, or characterized by extensive central or paracentral corneal spread) reported a recurrence rate of 25%, slightly higher than those usually reported for nondiffuse lesions. A single randomized controlled trial was performed for CIN of any dimension or clock hours of limbal involvement, using MMC 0.04% 4 times a day for 3 weeks. The authors reported a complete resolution in 24 of 26 patients.41
The Use of Mitomycin C in Conjunctival Squamous Cell Carcinoma
Mitomycin C seems to be most frequently used as adjuvant or neoadjuvant therapy for SCC and rarely used as a sole therapy for invasive OSSN (Table 4).3 The dosage of MMC used as adjuvant treatment for previously excised SSC ranges from 0.01% through 0.02% to 0.04%.2-4,42 The largest group was reported by Rahimi et al48 (17 patients). Using topical MMC at 0.04% as an adjuvant treatment, these authors reported 5 recurrences (29%) during follow-up. Other authors reported their experience with MMC as a neoadjuvant chemotherapy agent for tumor reduction before the surgical resection (at least 2 weeks) of thick extensive conjunctival SCC, obtaining interesting results.10,18,49 However, most authors recommended the use of MMC as a primary therapy only if excision is not possible, as in extensive or diffuse lesions.43,50
The Use of Mitomycin C in Other Tumors
Rare case reports in the literature analyze the use of MMC in the treatment of sebaceous carcinoma, as a pre-, intra-, and postoperative therapy, obtaining promising results. Chemotherapy with MMC seems to be suitable for treating these lesions because of the ill-defined and multifocal nature of the intraepithelial involvement.50 Both 0.04% and 0.02% dosages were used.2,50
Ocular Toxicity of Mitomycin C
Tissue side effects secondary to the use of topical MMC can persist for many years after the cessation of treatment, similar to those caused by ionizing radiation.2 Topical MMC toxicity occurs in a predictable and dose-dependent pattern and is usually more severe than that caused by 5-FU and IFN.4,50 Patients receiving shorter courses and lower drug concentrations (0.02%) seem to experience fewer severe adverse effects than those receiving longer or multiple courses, or using topical MMC at higher concentrations (0.04%).2 Patients usually experience transient adverse effects, such as conjunctival hyperemia and chemosis, tearing, punctate epithelial keratopathy, and/or toxic keratoconjunctivitis. These adverse effects are managed by adding topical steroid or nonsteroidal anti-inflammatory drugs (NSAIDs) or stopping the topical chemotherapy.4,13,15,23,51 Different cases of treatment discontinuation secondary to MMC adverse effects were reported.13 Punctal stenosis secondary to the use of topical MMC has been also reported.12,15,35 The incidence of this adverse effect should be reduced by occluding the lower punctum for a few minutes after instilling the drug.12,15,35 Other rare adverse effects include corneal haze, cataract, epithelial defects, disciform keratitis, and periocular dermatitis.13,15 Rare cases of limbal stem cell deficiency were also reported.13,17,38 When used as adjuvant chemotherapy to surgical excision, postoperative MMC does not prevent wound closure or cause corneo-conjunctival melting, if instituted after epithelial healing has occurred.2
Five-fluorouracil is a cell-cycle-specific pyrimidine analog, an antimetabolite that inhibits thymidylate synthetase, preventing DNA and RNA synthesis.50,52-54 Five-fluorouracil exerts its toxicity in active proliferating cells and the main mechanism of action is limited to cells in the S-phase of the cell cycle. Dormant cells are able to proliferate after treatment has been discontinued. Fivefluorouracil is effective against rapidly dividing tumor cells in the epithelium but does not seem to affect normal cells or corneal stem cells.50,52-54 Therefore, 5-FU seems to have a selective cytotoxicity to the dysplastic epithelium. Five-fluorouracil is soluble in water and when prepared in aqueous solution remains stable for at least 3 weeks. Compared with MMC, 5-FU does not require refrigeration or light protection.50,52-54
The Use of 5-Fluoruracil in OSSN
De Keizer et al55 first reported, in 1986, the use of 1% 5-FU as sole treatment of noninvasive OSSN with successful results. Subsequently, Yeatts et al54 and Midena et al52,56 reported other successfully treated cases using the same drug dosage (1%). This dosage still remains the standard one, but it is used in variable therapeutic regimens. Compared with MMC and IFN-α2b, relatively few papers have been published about the use of topical 5-FU (Table 5).46,47,52,54-65 Joag et al65 recently reported the use of 1% 5-FU (4 times daily for 1 week followed by 3 weeks of suspension, for an average of 4 cycles) as a primary treatment of 44 eyes affected by OSSN. These authors reported a lack of response in 4 cases. Moreover, 4 cases were switched to a different therapy for various reasons, and 4 cases recurred during followup (1 at 3.7 years after the treatment). These authors also noted that the presence of nodularity increased the risk of recurrence approximately 11-fold. Unfortunately, a limit of this study is that histopathology was reported only for 16 patients. In 2011, Parrozzani et al60 reported 41 OSSN cases retrospectively analyzed for detecting long-term side effects of 5-FU. Of these, 21 patients were affected by intraepithelial dysplastic lesions treated with topical 1% 5-FU 4 times per day for 4 weeks as primary or adjuvant treatment. In this case series, a single case of tumor recurrence was documented. Bahrami et al46 recently reported the largest series of patients affected by noninvasive and localized OSSN treated by 5-FU as adjuvant treatment (as a part of a larger study comparing MMC and 5-FU as adjuvant treatment for OSSN), using 1% 5-FU 4 times per day continuously for a period of 2 weeks. These authors reported a single case of recurrence in a patient who had not completed the protocol. Rudkin et al,47 using a regime of 2 weeks of continuous therapy of 1% 5-FU, described the effectiveness of 5-FU in primary and recurrent OSSN, also in selected cases refractory to topical MMC. In a recent paper, Parrozzani et al61 reported a response rate of 95% and 85% in 20 cases of low-grade and 13 high-grade dysplasia, respectively, using 1% 5-FU as sole treatment (Fig. 2). No correlation was found between late recurrences (0% and 17%, respectively) and primary incomplete response to chemotherapy or number of treatment courses. Furthermore, multivariate analysis showed that the major limitations of topical chemotherapy with 5-FU were tumor thickness (more than 1.5 mm) and multifocality.
Five-fluorouracil seems to be most frequently used as adjuvant or neoadjuvant therapy for SCC and rarely used as a sole therapy.59,60,64 Our group has recently reported 8 cases of SCC treated with 5-FU as a sole treatment, obtaining a response rate of 50% with a mean follow-up of 105 ± 32 months.61 Three other patients affected by SCC were treated with 1% 5-FU as sole treatment by Joag et al.65 One patient showed full resolution after 3 cycles of 5-FU, a single patient did not respond to treatment after 6 cycles, and another patient was switched to a different treatment.
Ocular Toxicity of 5-Fluorouracil
The adverse effects of 5-FU are mild and transient, consisting of hyperemia and superficial keratitis.3 Transient keratoconjunctivitis is present in most patients treated continuously for 28 days during the third or fourth week of treatment and can be easily controlled with topical steroid.52 Conversely, Yeatts et al54 did not find significant side effects using a pulsed dosing regimen.
Five-fluorouracil toxicity seems to be less severe than that caused by MMC, with rarer cases of corneal epithelial defects, erythema of the eyelid skin, and epiphora. Rare cases of treatment interruption because of transient superficial toxicity were also reported.3,46,47,62,65 Furthermore, Parrozzani et al60 already demonstrated (by in vivo confocal microscopy) that topical chemotherapy with 1% 5-FU is a safe treatment in the long-term for all corneal layers, revealing no long-term differences between the treated and control (fellow) eyes.
IMMUNOTHERAPY OF CONJUNCTIVAL TUMORS
Interferons are a group of glycoproteins with antiviral, antimicrobial, and antineoplastic activities. They act at cell surface receptors prolonging the length of the cell cycle, downregulating oncogenes, and promoting tumor suppressor genes.3,4 Their systemic use is established for the treatment of hairy cell leukemia, condyloma acuminate, Kaposi sarcoma in AIDS, and hepatitis C.3,4 Interferon-α2b is the recombinant form of interferon-α, and it was applied both topically and in subconjunctival/perilesional injections to conjunctival tumors (Table 6).2 Its antiproliferative proprieties seem to be related to the promotion of the immune response through an activation of host cytotoxic effector cells.2 Even if comparable rates of resolution were reported with both treatment modalities, topical application is preferred due to its better safety profile and avoidance of systemic effects. Interferonα2b needs refrigeration to ensure 1-month stability. Although the costs vary widely, IFN-α2b is the most expensive agent compared with 5-FU and MMC.3,50,66
The Use of IFN-α2b in Conjunctival Pigmented Lesions
Published data on the use of IFN-α2b for the treatment of pigmented lesions are limited. The regimen of 1 million IU/mL 5 times a day as adjuvant therapy was reported in 1 series of 5 conjunctival melanomas by Finger et al.67 Four of these 5 patients who had failed previous excision or topical MMC had resolution of the lesion. Herold et al68 reported a series of 9 patients affected by PAM with atypia and treated by IFN-α2b, 1 million IU/mL 5 times a day in 6-week cycles. Of these, 7 showed complete regression, 3 patients required a second cycle, and 1 patient needed a third cycle. One patient required both a fourth cycle of therapy and additional surgery to control the disease. Recently, Garip et al69 reported 5 patients with biopsy-proven PAM with atypia and 7 patients affected by conjunctival melanoma that were treated with topical IFN-α2b. Compared with pretreatment lesion dimension, the mean decreases in tumor size were 66% after the first cycle, 55% after the second cycle, and 74% after the third cycle.
The Use of IFN-α2b in Conjunctival OSSN
A large number of papers were published on the use of IFNα2b in the treatment of OSSN after the first report by Maskin et al in 1994.70 Interferon-α2b may be effective as a primary treatment and also as a salvage treatment, especially when prior surgical excision has failed.3,70 Different regimens were found to be effective, and the most common dosages range from 1 to 3 million IU/mL, 4 times daily, used at least until complete clinical resolution of the lesion.3,70 Karp et al66,71-73 published several reports about the use of IFN-α2b in OSSN and, in 2010, Galor et al71 reported a comparison between 21 eyes treated with 1 million IU/mL and 12 eyes with 3 million IU/mL. No statistical differences in clinical resolution of primary versus recurrent CIN (81% and 92%, respectively) were reported. The same authors reported comparable average time of resolution (2.8 and 1.9 months, respectively) using these different drug concentrations.71 Interferon-α2b has been shown to be effective, with clinical resolution of around 80% of the cases in the larger series reported. For example, Holcombe et al74 reported clinical resolution of 8 of 10 cases of recalcitrant OSSN with topical IFN-α2b (1 million IU/mL) 4 times a day until clinical resolution. All patients had been previously treated with topical MMC with lack of response. Unfortunately, 1 of the enrolled patients developed orbital invasion and underwent orbital exenteration. Thus, the authors conclude that IFN-α2b may be a valid option for extensive or recurrent lesions, but invasive disease should not be managed with IFN-α2b alone, as this could delay definitive surgical intervention and extension of the malignancy. Sturges et al75 and Nanji et al,72 analyzing respectively 29 and 98 patients, reported no significant differences in the disease control using surgery or IFN-α2b. Unfortunately, the lack of histology in conservatively treated patients may be a potential bias of these studies. However, a recent literature-based decision analysis identifies surgical excision followed by topical IFN-α2b for cases with positive surgical margins as the most effective strategy for minimizing persistence or recurrence of OSSN.76
The Use of IFN-α2b in Conjunctival Non-Hodgkin Lymphoma
The majority of conjunctival lymphomas are B-cell non-Hodgkin lymphomas (98%). Of these, the most frequent subtypes are MALT lymphoma (81%), followed by follicular lymphoma (8%), diffuse large B-cell lymphoma (3%), and mantle cell lymphoma (3%).77 At present, external beam radiotherapy is the treatment of choice for MALT and follicular lymphoma, whereas diffuse large B-cell lymphoma, mantle cell lymphoma, and T-cell lymphomas are mainly treated with chemotherapy. The use of local immunotherapy with IFN-α, injected subconjunctivally, was reported as a promising treatment of conjunctival MALT lymphoma.77 Blasi et al,78 in 2012, reported the largest series (20 eyes of 16 patients) of histologically proven conjunctival MALT lymphoma. These authors used 1.5 million IU of IFN-α subconjunctivally injected inside the lesion, 3 times weekly for 4 weeks. If there was even a minimal response, a further cycle of 1,000,000 IU 3 times weekly for 4 weeks was administered. A complete response was obtained in 15 eyes (75%) at the end of the first cycle and in 5 eyes (25%) after further cycles. Seventeen eyes (85%) showed no local recurrence after a median follow-up of 65 months. Three eyes (15%) demonstrated recurrence at variable points after treatment.
Ocular and Systemic Toxicity of IFN-α2b
Topical interferon has fewer adverse effects, compared with other topical chemotherapeutic agents, such as mild chemical conjunctivitis and corneal punctate epithelial erosions.3,4,53 A relatively higher frequency of adverse effects occurs when using a dose of 3 million IU.71 When injected subconjunctivally, transient local adverse effects were common, including injection, irritation, corneal punctate epithelial erosions, and corneal and eyelid edema. Local adverse effects are associated with mild systemic adverse reactions, such as flu-like symptoms, fever, and myalgia.3,66 No fatal or carcinogenic adverse effects have been reported with subconjunctival or topical use of IFN-α2b.3,4
OTHER DRUGS AND COMBINATION THERAPIES
Immunotherapy with monoclonal antibodies, particularly rituximab and daclizumab, has been proposed as a treatment option for patients with conjunctival lymphoma. The existing studies suggest that intralesional rituximab is well tolerated and produces a good response, with approximately 75% of patients being progression-or recurrence-free during a 1-year follow-up period.77
Bevacizumab is a full-length humanized monoclonal antivascular endothelial grow factor (VEGF) antibody that was initially approved by the US Food and Drug Administration (FDA) for the treatment of patients with colorectal cancer. A case series of 6 eyes affected by conjunctival intraepithelial neoplasia and treated with topical bevacizumab was recently published, suggesting the possible efficacy of this drug as neoadjuvant therapy. A dose of 5 mg/mL bevacizumab was administered 4 times daily for a period of 8 weeks. All lesions were responsive to treatment and surgery was not necessary in 2 cases. Moreover, no recurrences were observed during a follow-up period of 6 months. No systemic and local side effects were documented.79 Unfortunately, after analyzing other case reports on the use of topical anti-VEGF for the treatment of recalcitrant OSSN, resolution of the disease seems to occur in a minority of cases.3
Other agents were proposed to treat pigmented and nonpigmented conjunctival epithelial tumors, such as retinoic acid, urea, the immunologic adjuvant dinitrocholorbenzene, and cidofovir.53 Unfortunately, no data are available to better address their efficacy and safety in the treatment of conjunctival tumors.53 A peculiar case of a patient with a clinical diagnosis of OSSN who refused traditional therapies and obtained complete resolution of the lesion using a commercially available aloe vera preparation was reported by Damani et al.80
Many cases of combination therapy were reported in the attempt to have a synergic therapeutic effect with fewer side effects. Interferon was administered after a marked size reduction of PAM with atypia induced by MMC to complete treatment limiting MMC local toxicity.19 Zaki et al42 reported the use of MMC 0.01% combined with cyclosporine A 0.05% 4 times a day for 12 weeks after surgery for conjunctival intraepithelial neoplasia involving the cornea in 6 eyes and SCC in 4 eyes. No recurrence was reported. The use of this combination may provide a synergic effect leading to an effective result limiting MMC side effects.
Growing evidence shows a more prominent use of topical therapies for conjunctival tumors, both as a sole treatment or in conjunction with surgery.65 The reasons for this trend are the possibility to treat the entire ocular surface, potentially eliminating subclinical tumor cells at sites different from the clinically evident tumor and to avoid the complications of surgical excision. Topical chemotherapy results are particularly attractive in diffuse, multifocal lesions involving the limbus and the cornea, or when positive margins are detected after surgery.2,53 Nevertheless, a standard protocol for the use of different drugs in different conjunctival tumors has not yet been identified. The rarity of these diseases limits our possibility to have comparable study results, and clinical decisions are still left to the single physician on the basis of personal experience in different patient populations. However, some conclusions can be drawn from the current literature.
Mitomycin C proved to necessitate a shorter period of administration compared with others and some patients may prefer a particular regimen (1 or 2 treatment weeks per month with MMC and 5-FU is easier than the daily dosing of IFN for months). Five-fluorouracil does not require refrigeration, unlike the others drugs, and presents fewer side effects than MMC. Interferon has the best safety profile (when topically administered) but a longer period of administration.3,4
At present, a larger series on OSSN reported similar response frequency to topical 5-FU, IFN (82-100% for both), and MMC (76-100%), even if distinction between invasive and preinvasive lesions is not always clear and in several series patients underwent different previous treatments because of the retrospective design of most studies.3,47,65 With regard to pigmented lesions, most series underline that MMC should be considered the chemotherapeutic agent of choice for PAM, but IFN seems to be an effective alternative. Patients that present with inadequate or incomplete response to one agent may respond to another drug (MMC or IFN).53
Recently a preliminary correlation between mutant genes and a history of lack of response to a specific topical therapy (in particular IFN-α2b) has been reported, suggesting a possible new way to decide the best therapy in advance.73 Furthermore, several drugs actually used in the treatment of a variety of systemic malignancies are under evaluation in vitro for their efficacy in different conjunctival tumors, alone and in combination with the already used topical chemotherapies.5
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