Esophageal cancer patients are often associated with multiple primary cancers (MPC). The aim of this study is to evaluate the effect of MPC on prognosis in esophageal cancer patients treated by radiotherapy. Between 2001 and 2008, esophageal cancer patients treated by definitive radiotherapy at Gunma Cancer Center were retrospectively reviewed. Exclusion criteria were preoperative or postoperative radiotherapy, palliative radiotherapy, follow-up of <6 months, radiation dose of <50 Gy and no information on MPC. We analyzed 167 esophageal cancer patients and 56 (33.5%) were associated with MPC. Gastric cancer was the most frequent tumor (38.2%), followed by head and neck cancer (26.5%). Median follow-up time was 31.5 months (range 6.1-87.3 months). Patients with MPC included more stage I/II esophageal cancer than those without MPC (66.1% vs. 36.9%, P < 0.01). The 5-year overall survival rate for esophageal cancer with MPC was relatively better than those without MPC (46.1% vs. 26.7%), although the difference did not reach statistical significance in univariate analysis (P = 0.09). Stage I/II esophageal cancer patients had a significantly better overall survival than stage III/IV patients (P < 0.01). Among esophageal cancer patients with MPC, there was no difference in overall survival between antecedent and synchronous cancer (P = 0.59). Our study indicated that the prognosis of esophageal cancer patients treated by radiotherapy was primarily determined by the clinical stage itself, but not the presence of MPC.
Keywords: antecedent cancer; esophageal cancer; multiple primary cancers; radiotherapy; synchronous cancer.