February 2016, Vol. 5, No. 1
Case: Clinically Node-Negative Merkel Cell Carcinoma
Merkel cell carcinoma (MCC) is a rare and aggressive cancer with a case fatality rate of 33%. Delayed diagnoses of MCC are common, which results in patients often presenting at advanced stages, said Manisha Thakuria, MD, at the 2015 World Cutaneous Malignancies Congress.
The optimal care of MCC is debated. There are no randomized controlled trials to provide guidance. Guidelines for management from the National Comprehensive Cancer Network are very broad. The following case outlines the management of MCC in a younger patient with clinically node-negative disease.
A 43-year-old woman with a lesion on her right dorsal hand presented after failure of topical wart treatment to resolve the lesion. Biopsy of the lesion reveals a 1-cm MCC. What is the case for imaging before treatment?
At the Dana-Farber Cancer Institute, imaging studies are obtained at baseline for accurate staging and prognosis, keeping in mind that up to 8% of patients present with distant metastatic disease at the time of diagnosis. Up to 22% of patients are upstaged with imaging.
“You want to be able to treat metastatic disease earlier, and moreover, avoid any unnecessary procedures in patients who are not going to derive any benefit from them,” said Thakuria, Director, Merkel Cell Carcinoma Clinic, Dana-Farber/Brigham and Women’s Cancer Center, Boston, MA.
A PET/CT scan can provide a scalp-to-toes image (“melanoma protocol”), which is useful because up to one-third of metastases are going to occur in the skin or soft tissues, and can detect metastatic lesions ≥7 mm. The sensitivity of PET/CT is 90%, and the specificity is 98%. Treatment planning may be adjusted based on the results of PET/CT.
For initial staging, metabolic imaging is suboptimal for detection of brain metastases. “Getting a PET/CT by no means replaces a sentinel lymph node biopsy for detection of micrometastatic disease,” she said. “It’s also important to note that not every Merkel cell tumor is FDG [fludeoxyglucose] avid, although the vast majority of them are.”
In addition to the workup, a multidisciplinary tumor board consultation should be considered, given the complexity of MCC.
The patient underwent PET/CT with her initial workup and was found to have disease in 2 lymph node basins—epitrochlear and right axilla.
Treatment of the individual patient is based on whether the disease clinically appears limited to the skin or involves the lymph nodes or is distantly metastatic. For patients with clinically node-negative disease, the primary management of MCC is surgical. “Sentinel lymph node biopsy followed by wide local excision is probably what the vast majority of our patients are getting,” said Thakuria.
Based on the results from the PET/CT and her young age, the patient wanted to be aggressive with treatment. Surgery was performed at all 3 sites, including completion lymph node dissection to the axilla, followed by radiation to all 3 sites.
Lymph node status is the most consistent predictor of survival. If only clinical nodal staging is performed, micrometastatic disease will be missed in up to one-third of patients, even in patients with small tumors (eg, clinical stage I). In the Memorial Sloan Kettering database, almost one-fourth of patients with clinically stage I disease were upstaged to stage IIIA based on pathologic staging of the node, said Thakuria.
With excision, “the general take-home point is that if you can get margins, that’s great, but don’t sacrifice getting margins at the expense of delaying radiation. It is an effective means of secondary treatment,” she said. “It has been shown that if you delay the radiation therapy, people have worse outcomes. In certain locations we’ll take very small margins, then close and get them right to radiation.”
The patient is 5 years out from treatment, with no evidence of disease.
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