The rate of recurrence of the rare but aggressive skin cancer Merkel cell carcinoma (MCC) is markedly higher than that for invasive melanoma, squamous cell carcinoma, or basal cell carcinoma, and more than half of all patients with stage IV disease will have a recurrence within 1 year of definitive therapy, results of a new study show.
A study of 618 patients with MCC who were enrolled in a Seattle-based data repository shows that among all patients, the 5-year recurrence rate was 40%. The risk of recurrence within the first year was 11% for patients with pathologic stage I disease, 33% for those with stage IIA/IIB disease, 45% for those with stage IIIB disease, and 58% for patients with pathologic stage IV MCC.
Approximately 95% of all recurrences happened within 3 years of the initial diagnosis, report Aubriana McEvoy, MD, from the University of Washington in Seattle, and colleagues.
“This cohort study indicates that the highest yield (and likely most cost-effective) time period for detecting MCC recurrence is 1 to 3 years after diagnosis,” they write in a study published online in JAMA Dermatology.
The estimated annual incidence of MCC in the US in 2018 was 2000 according to the American Cancer Society. The annual incidence rate is rising rapidly, however, and is estimated to reach 3284 by 2025, McEvoy and colleagues write.
Although MCC is known to have high recurrence rates and is associated with a higher mortality rate than malignant melanoma, recurrence rate data are not captured by either the Surveillance, Epidemiology, and End Results (SEER) database or by the National Cancer Database. As a result, estimates of recurrence rates with MCC have been all over the map, ranging from 27% to 77%, depending on the population studied.
But as senior author Paul Nghiem, MD, PhD, professor and chair of dermatology at the University of Washington School of Medicine, Seattle, told Medscape Medical News, recurrence rates over time in their study were remarkably consistent.
“The biggest surprise to me was that when we broke our nearly 20-year cohort into three 5- or 6-year chunks, every one of the groups had a 40% recurrence rate, within 1%. So we feel really confident that’s the right number,” he said.
Nghiem and colleagues report that in contrast to patients with MCC, approximately 19% of patients with melanoma will have a recurrence, as will an estimated 5% to 9% of patients with squamous cell carcinoma and 1% to 10% of patients with basal cell carcinoma.
The fact that recurrence rates of MCC have remained stable over time despite presumed improvements in definitive therapy is disappointing, Nghiem acknowledged. He noted that it’s still unclear whether immunotherapy will have the same dramatic effect on survival rates for patients with MCC as it has for patients with malignant melanoma.
The high recurrence rates following definitive therapy for patients with early-stage disease was a novel finding, commented Shawn Demehri, MD, PhD, director of the High Risk Skin Cancer Clinic at Massachusetts General Hospital in Boston.
“When you’re looking at patients with stage I or stage II and they have definitive surgery but still have recurrences at a higher rate than melanoma brings home the point that these are among the most aggressive tumors of the skin,” he said in an interview with Medscape Medical News.
The high recurrence rates seen with MCC are attributable to a variety of factors.
“This is a rare cancer of mostly older individuals with a lot of comorbidities, and also a cancer that, even though it is a primary cancer, might be detected a little later than even a melanoma primary tumor, just because of the nature of the neuroendocrine tumor cells,” he said.
Demehri was not involved in the study.
The study cohort consisted of 618 patients with MCC. The median age of the patients was 69, and 227 (37%) were women. The patients were enrolled within 6 months of their diagnosis in the prospective data repository from 2003 through 2019. Of this group, 223 had a recurrence of MCC.
As noted, there was a high risk of recurrence within 1 year, ranging from 11% for patients with pathologic stage I tumors to 58% for those with stage IV disease, and 95% of all recurrences occurred within 3 years of definitive therapy.
To get a better picture of the natural history of MCC recurrence, the investigators studied a cohort of patients with pathologically confirmed MCC who were prospectively enrolled from January 2003 through April 2019 in a data repository maintained at the University of Washington.
In addition to disease stage, factors associated with increased recurrence risk in univariable analyses include immunosuppression (hazard ratio [HR], 2.4; P < .001), male sex (HR, 1.9; P < .001), known primary lesion among patients with clinically detectable nodal disease (HR, 2.3; P = .001), and older age (HR, 1.1, P = .06 for each 10-year increase).
Of the 187 patients in the cohort who died during the study, 121 died from MCC. At 4 years after diagnosis, MCC-specific survival rates were 95% for patients with pathologic stage I, 84% with stage IIA/IIB, 80% with stage IIIA, 58% with stage IIIB, and 41% with stage IV.
Evidence supports close monitoring within the first 3 years for patients with stage I–II MCC. Local recurrence within or adjacent to the primary tumor scar was associated with a 5-year MCC-specific survival rate of 85%, compared with 88% of patients with stage I or II disease who did not have recurrences.
“Because more than 90% of MCC recurrences arise within 3 years, it is appropriate to adjust surveillance intensity accordingly. Stage- and time-specific recurrence data can assist in appropriately focusing surveillance resources on patients and time intervals in which recurrence risk is highest,” the authors wrote.
“If you’re a patient who has not had your cancer come back for 3, 4, or 5 years, you can really cut down on the intensity of your follow-up and scans,” Nghiem said.
“We do now have two excellent blood tests that are working very well, and we have really good ways to detect the cancer coming back early, and that’s important, because we have potentially curative therapies that tend to work better if you catch the cancer early,” he said.
The study was supported by the National Institutes of Health. Nghiem reported personal fees and institutional support outside the study from several companies and patents for Merkel cell therapies with the University of Washington and University of Denmark. Demehri has disclosed no relevant financial relationships.
JAMA Dermatol. Published online February 23, 2022. Abstract
Neil Osterweil, an award-winning medical journalist, is a long-standing and frequent contributor to Medscape.