PARK CITY, UTAH Treat Merkel cell carcinoma aggressivelyrecurrences are always fatal, Dr. Mary E. Maloney told physicians at a clinical dermatology seminar sponsored by Medicis.
"You have one chance to cure this disease. When treating a primary tumor, you use whatever you can to get a cure," counseled Dr. Maloney, director of dermatologic surgery at the University of Massachusetts, Worcester.
While stage I disease has a 100% survival rate, she said mortality is 11% for stage II disease. Should there be distant metastasis, the hallmark of stage III disease, mortality climbs to 100% (J. Clin. Oncol. 1988;6:186373).
By the time a recurrence is diagnosed, the disease has already spread, according to Dr. Maloney. "We don't have the luxury of recurrence," she said, describing this rare skin cancer as "a very difficult tumor to diagnose and to cure."
Merkel cell carcinoma strikes men and women equally, she said, putting the incidence at 500 cases per year. Though the age range is 1597 years, the average is 69 years, as most patients are older.
Most tumors occur in sun-exposed areas, according to Dr. Maloney. Immunosuppression also appears to play a role, as Merkel cell carcinoma is more common in transplant patients and people with chronic lymphocytic leukemia than in the general population.
Because they can appear benign when small, these rare tumors are often 2 cm at presentation, said Dr. Maloney. They range from pink to red, and 20% have palpable nodes at presentation.
Ruling out other carcinomas is the clinician's first step, she said, recommending that the physical examination include a lymph node exam with careful palpitation of the entire area for deep nodules and a careful exam for satellitosis.
Electron microscopy and immunohistochemistry are important in making the diagnosis, she added. Positive staining for cytokeratins 8, 18, 19, and 20 would be a key marker, along with neuron-specific enolase, synaptophysin, chromogranin, and neurofilaments.
Neither size nor duration is a prognostic factor, according to Dr. Maloney, but lymph node involvement and tumor location are predictive. She estimated survival as 70%80% for those with lymph node-negative tumors and less than 48% for those that are lymph node-positive. Survival is higher for lesions on a limb than on the trunk.
Increasingly, Mohs surgery is being used for Merkel cell carcinoma, according to Dr. Maloney. She said the standard Mohs technique allows for true margin control and removal of all inflammation. She advocated removing an additional margin, usually about 1 cm, after all clear sections are obtained.
Dr. Maloney also recommended adjunctive radiation treatment to improve local and regional control. Retrospective studies have not shown it to reduce mortality, but she predicted that when prospective studies are done, they will show improved survival.
With truncal lesions, she advocated adjunctive radiation therapy whether a sentinel node biopsy shows the patient's lymph nodes to be positive or negative. If the nodes are positive, she said to do full node dissection as well.
When lesions are not on the trunk, her advice is the same. She disagreed with physicians who advocate no further therapy if biopsy shows sentinel nodes to be negative. "We have one chance to cure this disease," she reiterated. "Therefore, I believe radiating … is the best shot at curing the patient."
Chemotherapy is also an option, but she cautioned that it is not life-saving. Dr. Maloney said 42 different regimens have been tried, with response rates ranging from 50% to 65%. Yet survival with chemotherapy is only 9 months for patients with metastatic disease.
"While Merkel cell appears chemosensitive, it is seldom cured with chemotherapy," she said.