Primary tumor site may predict Merkel cell carcinoma mortality

Localized Merkel cell carcinoma tumors with a primary site in the neck and scalp were associated with the highest 5-year probability of mortality, according to a study.

“Merkel cell carcinoma (MCC) primary site has not been fully investigated as a potential prognostic factor,” Christopher R. Cullison, BS, of the department of dermatology at Case Western Reserve University School of Medicine in Cleveland, and colleagues wrote.

In the current retrospective analysis of the of the Survival, Epidemiology and End Results (SEER) database, Cullison and colleagues assessed incidence MCC mortality as a function of the primary site of tumors.

Patients undergoing cancer therapy between 1973 and 2016 were eligible for inclusion. The researchers performed a competing risk analysis that accounted for the impact of primary tumor site on disease-specific mortality. Estimates for cumulative incidence of Merkel cell carcinoma-specific mortality (CMMI) at 5 years were reported.

The initial search yielded data for 9,407 MCC patients (median age at diagnosis, 77 years; age range, 11-105 years; 62.4% male; 95.3% white). Localized disease was reported in 6,305 patients, while 2,397 reported regional metastasis and 705 experienced distant metastasis.

Results showed that the primary site of the tumor predicted CMMI. However, variety in these results was seen in tumor stage at diagnosis.

Among localized tumors, those in the scalp or neck were associated with the highest probability of mortality at 5 years as assessed by CMMI, at 26%. Localized truncal tumors had a CMMI rate of 25.9%.

Among tumors with regional metastasis, those in the lip had a CMMI of 56.7%. In addition, lip tumors with distant metastasis also carried high CMMI risk, at 82.1%.

The lowest CMMI rates were all seen in eyelid tumors, including those that were localized (14.3%), regionally metastatic (34.8%) and occurring with distant metastases (39.3%).

The CMMI rate for regionalized MCC with unknown primary site demonstrated a 5-year probability of mortality of 31.9%. This rate was 58.9% for tumors of unknown primary site with distant metastases.

The researchers noted that the findings are limited because tumor data were missing for many patients, precluding patient stratification by American Joint Committee on Cancer guidelines.

“Probability of MCC disease-specific death varies by primary site,” the researchers concluded. “The primary site of the tumor may be useful as a prognostic indicator for MCC.”