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Study: Sentinel biopsy of limited help in some patients after conjunctival melanoma removal

Early treatment of the primary lesion and close postop follow-up are the best means for enhancing patient survival, surgeon says.

ByMichael Piechocki

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Sentinel lymph node biopsy is likely to be more helpful for detecting metastasis in some patients after surgical removal of conjunctival melanoma than in others, a Finnish study concluded.

According to Seppo Tuomaala, MD, FEBO, patients who have nonlimbal tumors or tumors that are more than 2 mm thick in any location at the time of primary diagnosis are more likely to benefit from sentinel lymph node biopsy.

Patients with limbal melanomas or tumors that are less than 2 mm thick are less likely to have affected lymph nodes, he told Ocular Surgery News in an interview.

Dr. Tuomaala and Tero Kivelä, MD, FEBO, conducted a retrospective, population-based study to evaluate the overall survival pattern of patients with disseminated conjunctival melanomas. Although these patients did not undergo sentinel biopsies, the aim of the study was to identify characteristics of those patients who in the future would most likely benefit from the procedure.

“As a matter of fact, with very rare exceptions, when a thin limbal tumor metastasizes there have been first a variable number of recurrences, often in nonlimbal locations,” Dr. Tuomaala said.

“We believe sentinel lymph node biopsy should be evaluated in all patients that fulfill the above criteria. One study is under way at M.D. Anderson Cancer Center in Houston. However, because there is no conclusive evidence even in patients with cutaneous melanoma that life prognosis is improved by this procedure, for the time being we do not recommend sentinel lymph node biopsy in low-risk patients,” he said.

“Sentinel lymph node biopsy provides accurate information for staging the extent of the disease and helps to select patients who may benefit from additional treatments that hopefully will emerge in the future,” he said.

Sentinel lymph node biopsy

According to Dr. Tuomaala, sentinel lymph node biopsy is commonly used in patients with skin melanomas. It is a relatively invasive procedure that must be done in most centers with the cooperation of plastic surgeons, radiologists and pathologists.

The term “sentinel” refers to the first lymph node or nodes receiving lymph drainage from the tumor area, and thus the first lymph node that the cancer is likely to spread to from the primary tumor.

In performing the procedure, 200 µCi of sulfur colloid technetium-99mis is injected at the site of the tumor and is followed by serial lymphoscintography, which monitors drainage of the lymph. The location of the involved lymph nodes is then confirmed using a gamma probe. Blue dye is injected intraoperatively to stain the affected nodes, which are then excised for pathologic examination.

Dr. Tuomaala said sentinel lymph node biopsy is based on the idea that metastasis is an orderly process that first involves the local lymph nodes. Theoretically, if nodal involvement could be detected early enough, the patient would be saved.

In practice, however, many patients present first with systemic metastases or simultaneously with local lymph node metastases and systemic metastases. He noted that it is possible these patients had subclinical lymph node metastases that could have been detected earlier using sentinel lymph node biopsy.

“Ophthalmologists should understand that the clinical behavior of conjunctival melanoma is very different from that of uveal melanoma, which metastasizes always hematogenously,” he said.

He explained that most cancers can spread both by lymphatic channels and hematogenously. Consequently, even if involved lymph nodes are removed, the patient may later develop systemic metastases, he said.

“The key question here is whether metastasis really is an orderly process first involving lymph nodes. Sentinel lymph node biopsy makes little sense if the disease has already spread systemically,” he said.

Reports on cutaneous melanoma suggest that survival may be improved using sentinel lymph node biopsy compared to elective removal of lymph nodes based on clinical suspicion of lymphatic metastasis.

“Common sense suggests that detecting micrometastases early in high-risk patients would be beneficial,” he said, noting this needs to be confirmed by large population-based studies.

Treatment of primary tumor

According to Dr. Tuomaala, conjunctival melanomas are normally treated by local resection combined with cryocoagulation of the surgical margins.

Many centers also use mitomycin-C postoperatively because studies have suggested it can help prevent recurrence, he said. Mitomycin also helps eliminate atypical primary acquired melanosis — the premalignant melanocytes — which are the most common precursory lesions of malignant conjunctival melanoma, he said.

He noted that in examining a suspected case, it is particularly important to evaluate the patient’s entire conjunctiva by everting the upper eyelid because the tumor can grow large at this location without the patient noticing.

For Your Information:

• Seppo Tuomaala, MD, FEBO, can be reached at the Department of Ophthalmology, Helsinki University Central Hospital, Haartmaninkatu 4 C, PL 220, FIN-00029, Helsinki, Finland; e-mail: seppo.tuomaala@hus.fi.

Reference:

• Tuomaala S, Kivelä T. Metastatic patterns and survival in disseminated conjunctival melanoma. Ophthalmology. 2004;111:816-821.

• Michael Piechocki is an OSN Staff Writer who covers ophthalmology in Europe, Asia and the Pacific region. He also specializes in oculoplastic topics.