E313: Clinical Implications of Collision Tumors on Long-Term Outcomes in Merkel Cell Carcinoma

ePoster Abstract Author(s)

Lily L. Nguyen, MD

Resident Physician
University of California - Irvine
Tustin, California, United States

Submitter(s)

Lily L. Nguyen, MD

Resident Physician
University of California - Irvine
Tustin, California, United States

Author(s)

Lily L. Nguyen, MD

Resident Physician
University of California - Irvine
Tustin, California, United States
YL

Yingjoy Li, BS

Medical Student
University of California - Irvine, United States
SY

Sarah Yuen, MD

Resident Physician
University of California - Irvine, United States
TT

Tu Tran, BS

Graduate Student
University of California - Irvine, United States
MY

Maki Yamamoto, MD

Physician
School of Medicine, University of California-Irvine, United States
TT

Thuy Tran, MD

Physician, School of Medicine
University of California - Irvine, United States

Introduction:

Merkel Cell Carcinoma (MCC) is a rare and aggressive skin cancer with neuroendocrine origin. Collision tumors represent a rare phenomenon resulting in the coexistence of two histologically distinct cancers within the same mass. The incidence and oncologic impact of collision tumors involving MCC remain unknown. The aim of this study is to determine the impact of simultaneous histologic distinct cancers within MCC tumors on survival.

Methods:

Patients diagnosed and treated for MCC were retrospectively identified. Patient demographics, tumor characteristics, stage, and treatment type were assessed. Kaplan Meier method was used to estimate overall survival (OS) and recurrence free survival (RFS). Multivariable Cox proportional regression was performed to identify predictors of survival.

Results:

A total of 170 patients were identified with MCC that underwent surgery, with 15 patients (8.8%) found to have collision tumors on final pathology. There were no significant differences in race, gender, stage, metastasis, neoadjuvant or adjuvant therapy between those with MCC versus those with MCC collision tumors. MCC collision tumors were more frequently observed in head/neck primary sites compared to non-head/neck sites (80% vs 20%, P=0.04). Among patients with positive nodal status, those with MCC collision tumors tended to have higher rates of extra-capsular extension compared to those with MCC alone (100% vs 12.0%, p=0.028). The 5-year RFS was significantly lower in the MCC collision tumors compared to MCC alone (55% vs 11%, P=0.004). Similarly, 5-year OS was substantially lower among those with MCC collision tumors (59.3% vs 33.9%, p=0.013). On multivariable analysis, the presence of a secondary metachronous collision tumor was a strong predictor of worse RFS (P=0.040), while receipt of adjuvant radiation was associated with improved RFS (P=0.036)

Conclusions:

MCC collision tumors are rare entities that may have distinct clinical behaviors and are likely associated with a more aggressive tumorgenesis. Because of its aggressive behavior, clinicians should be aware and vigilant of the existence and poor prognostic impact of these MCC collision tumors.

Learning Objectives:

Upon completion, participant will be able to define Merkel Cell Carcinoma collision tumors.
Upon completion, participant will be able to describe the impact of Merkel Cell Carcinoma collision tumors on oncologic prognostic outcomes when compared to Merkel Cell Carcinoma alone.
Upon completion, participant will be able to describe the differing tumor characteristics of Merkel Cell Carcinoma versus collision tumors that were demonstrated in this study.