The Merkel cell carcinoma (MCC) 5-year recurrence rate is 41% in a US cohort study – more than double the recurrence rate observed in melanoma.

The researchers said other skin cancer recurrence rates had been reported at about 19% for melanoma, 1-10% for BCC, and 5-9% for SCC.

The prospective study of 618 patients aged 11-98 years diagnosed with pathologically confirmed MCC between 2003 and 2019 found the risk of recurrence in the first year increased with cancer stage at diagnosis.

Stage-specific recurrence rates were 11% in stage 1, 33% in stage IIA/IIB, 30% in stage IIIA, 45% in Stage IIIB, and 58% in stage IV disease.

“At 5 years, 80% of patients with pathologic stage I cancer were without recurrence vs 28% of patients with stage IV,” the study said.

The study, published in JAMA Dermatology, found the vast majority of recurrences of the aggressive cancer occurred within the first three years.

“For all stages, the highest risk of recurrence occurred 1 to 3 years after initial treatment, and 94% of recurrences occurred within the first 3 years after initial treatment. This proportion ranged from 70% to 100% across stages.”

Most recurrences (60%) were distant metastatic disease.

“The high rates of distant metastatic recurrence emphasise the importance of surveillance imaging and serology testing (for patients who produce Merkel cell polyomavirus oncoprotein antibodies) because these recurrences are usually not detectable via clinical examination.”

Other risk factors for recurrence were immunosuppression (HR 2.4) and older age (HR 1.1) while protective factors were female sex (HR 0.5) and unknown site of primary tumour for patients with stage III disease (HR 0.4).

The MCC-specific survival rate was also strongly associated with stage – from 95% at 5 years for patients with pathologic stage I to 41% for pathologic stage IV.

“Of note, among patients who originally presented with stage I to II disease and experienced a local recurrence, MCC-specific survival was minimally affected and remained high (85% at 5 years).”

“Patients with stage I to II cancer may be relieved to know that their prognosis after a local recurrence is still relatively good. Patients with stage III cancer with any recurrence type should be strongly considered for immune therapy trials given their poor prognosis”

The researchers noted that their results largely reflect the clinical course of MCC before the era of immunotherapy.

“These data should assist in appropriately focusing surveillance resources on patients and time ranges in which MCC recurrence risk is highest (within the first 3 years after diagnosis) and potentially de-escalated after that time frame,” they concluded.

“Optimising surveillance intensity is an important goal because it would minimise unnecessary costs, capture recurrences earlier, and improve the chance that immune/systemic therapy would work because it tends to be more effective in the setting of low disease burden.”