Merkelcell.org Summary
Merkel cell carcinoma (MCC) is an aggressive type of skin cancer. It can spread to other parts of the body more often than many other skin cancers. Because of this, it is very important to find out how far the cancer has spread at the time of diagnosis.
Imaging scans, such as PET/CT or CT scans, are helpful because they can detect cancer that has spread to other areas of the body. In some patients, scans find hidden cancer that was not suspected based on the physical exam alone. When this happens, the cancer stage may be changed to a higher stage, also called “upstaging.”
Previous reports estimated that about 13% of patients with MCC are upstaged after imaging.
In this study, among the184 patients, about 1 in 5 (22%) of them had their cancer upstaged after baseline imaging. Most of these patients (78%) had cancer identified in their nearby lymph nodes, while 22% were found to have distant metastases. Having a larger tumor (greater than 2cm) increased the chance a patient was upstaged.
This data supports the universal practice of baseline imaging in MCC patients. The high rate of upstaging identified in this study provides a strong rational for obtaining imaging scans prior to surgery. Doing so allows surgeons and oncologists to plan the most effective treatment approach for individual patients.
Abstract
Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine malignancy with high rates of recurrence and mortality, especially for patients with lymph node and distant metastases.
1,2 Unlike other skin cancers, baseline imaging should be a universal step in MCC staging due to the high incidence of clinically occult nodal and distant metastases at diagnosis (13.2% in 1 single institution study).
3 While the National Comprehensive Cancer Network guidelines recommend baseline imaging,
4 its use in clinical practice remains inconsistent and not universally supported by insurance providers. Evidence to support baseline imaging would be strengthened by this study of patient and tumor characteristics associated with upstaging in MCC.
Herein, upstaging is defined as the identification of regional nodal and/or distant metastases on baseline imaging that were not detected on physical exam or history (ie, no palpable lymphadenopathy or evidence of distant metastases). Not all imaging-detected occult metastases were histopathologically confirmed; however, cases were classified as upstaged if they received treatment for metastatic disease.
This retrospective cohort study was conducted using an institutional repository of patients with biopsy-proven MCC who received treatment 2017-2023. Patients with MCC of unknown primary were excluded from analysis because these patients are often diagnosed after imaging demonstrates disease. Patients with incomplete staging data were also excluded.
In the resulting cohort of 184 patients, 162 (88.0%) received baseline imaging for histopathologically confirmed MCC, and 36 (22.2%) were subsequently upstaged. Upstaging incidence (∼22%) was similar between imaging modalities (positron emission tomography-computed tomography versus computed tomography without positron emission tomography). Among upstaged patients, 77.8% had clinically occult regional lymph node metastases (not detected via initial clinical exam or history), and 22.2% had clinically occult distant metastases (
Table I). Primary tumor size was significantly associated with upstaging: 35.2% (25/71) of patients with primary >2 cm were upstaged versus 12.1% (11/91) with primary ≤2 cm (
P = .001). Advanced age (≥80 years), male sex, primary tumor location, and immunosuppression were not significantly associated with upstaging (
Fig 1).