Comprehensive Analysis of Multiple Primary Cancers in Patients with Esophageal Squamous Cell Carcinoma Undergoing Esophagectomy.

OBJECTIVE To elucidate the latest epidemiology and risk factors for multiple primary cancers (MPCs), and the association between neoadjuvant chemotherapy (NAC) and postoperative metachronous cancer (PMC) in patients with esophageal squamous cell carcinoma (ESCC) who underwent esophagectomy. SUMMARY OF BACKGROUND DATA Background data to derive appropriate screening strategies are insufficient. METHODS This study consisted of three retrospective investigations. A total of 766 consecutive patients with ESCC who underwent esophagectomy between April 2005 and December 2019 were eligible for epidemiological analysis. Of these, 688 patients without missing data were analyzed for the risk of MPCs. In total, 364 patients who underwent NAC (115) and no preoperative treatments (249) were investigated for the association between NAC and PMC. RESULTS Of 766 patients, 288 (38%) patients experienced 357 MPCs in their life. PMCs identified after the completion of 5-year postoperative follow-up were significantly more advanced (P = 0.019). Male sex [hazard ratio (HR) = 3.04, P = 0.038], older age (HR = 2.39, P < 0.001), and diabetes mellitus (HR = 1.76, P = 0.034) were risk factors for preoperative metachronous cancers. Heavy smoking (HR = 1.70, P = 0.014) and drinking (HR = 1.61, P = 0.029) were risk factors for synchronous cancers. NAC significantly reduced PMC incidence (P = 0.043). NAC showed a trend to contribute to improved survival via reduced deaths from PMCs, although this did not reach significance (P = 0.082). CONCLUSIONS ESCC is associated with a high risk of MPCs. Continuing follow-up for PMCs after the completion of 5-year postoperative follow-up is important. NAC may reduce PMCs, representing a novel mechanism for improving survival in patients with locally advanced ESCC.