Among 288 patients with bone scan during pretreatment staging in the present study, bone metastasis was confirmed in 19 (6.6%) patients. Previous studies [13
] showed that the incidence of bone metastasis in esophageal cancer during pretreatment staging was 4-9%. In the present study, 10 (6.2%) of 161 patients receiving esophagectomy developed bone recurrence. In the previous studies, [6
] 5-9% patients developed bone recurrence after esophagectomy. Our results are similar to previous studies.
The results of bone scan were negative in 242 patients (84.0%), and only 5 patients of them developed subsequent bone metastases. The negative predictive value was high, and was not influenced by advanced stage (stages III and IV). However, the positive predictive value was low, especially in early-stage patients. Of the 46 patients who showed positive bone scan, 26 (56.5%) patients did not have bone metastasis, and in stage II patients, the positive predictive value was only 30.0%. It is important, therefore, the interpretation of bone scan need to take into consideration the context of clinical symptoms as well as any possible reasonable explanation for benign causes and the positive findings should be confirmed by further examinations such as X-rays, CT scans or MRI scans.
In our study, we did not find bone metastasis in 23 patients with stage I esophageal squamous cell carcinoma with a median follow-up of 1442
days, indicating that bone scan could be omitted in patients with stage I esophageal squamous cell carcinoma. Bhansali et al. [7
] also described that no recurrence occurred from 15 esophageal squamous cell carcinoma patients with pT1 tumor. However, Mariette et al. [24
] reported that for pT1 esophageal cancer, no recurrence occurred in 12 patients with tumor restricted to mucosa whereas recurrence was observed in 25 (31.8%) patients with tumor restricted to submucosa. But, the study from Mariette, et al. [24
] included both esophageal squamous cell carcinoma and adenocarcinoma, and they described that distant recurrences occurred more frequently with adenocarcinoma. Therefore, we suggest that bone scan may be unnecessary for esophageal squamous cell carcinoma restricted to mucosa. For esophageal squamous cell carcinoma restricted to submucosa, further study is needed.
As previously described, there have been doubts about the routine use of bone scan in esophageal cancer. Furthermore, the majority of histology type in previous reports on the role of bone scan in esophageal cancer is adenocarcinoma, not esophageal squamous cell carcinoma. Large series data regarding the value of routine bone scan in esophageal squamous cell carcinoma are scant. Multiple treatment choices including surgery alone, preoperative CCRT followed by surgery, definite chemoradiotherapy, radiotherapy alone can be applied to patients with resectable esophageal squamous cell carcinoma according to patient selection, physician preference, or comorbidity status. Such hampered our evaluation on the role of bone scan in esophageal sqaumous cell carcinoma. However, if bone scan has an appreciable role in the initial staging of esophageal squamous cell carcinoma, it is logical to expect significantly superior bone recurrence-free survival in patients receiving esophagectomy. Indeed, in our univariate analysis, absence of preoperative bone scan correlated with inferior bone recurrence-free survival, and it remained prognostically independent in multivariate comparison, suggesting that bone scan should be routinely performed before esophagectomy in patients with esophageal squamous cell carcinoma. Additionally, we found that lymph node involvement was associated with inferior bone recurrence-free survival. Previous studies [7
] also showed the correlation between lymph node involvement and distant organ recurrence. Our results further support previous findings.
In our series, bone metastasis was not detected in 23 stage I patients, indicating that bone scan could be omitted in stage I patients in the future. Hence, we perform subgroup analysis to evaluate the role of bone scan in stages II
III patients. In our univariate and multivariate analysis, absence of preoperative bone scan was significantly associated with inferior bone recurrence-free survival in stages II
III patients. We also found that absence of preoperative bone scan significantly correlated with inferior overall survival in stages II
III patients. It suggests that preoperative bone scan is a valuable tool in patients with esophageal squamous cell carcinoma, especially in patients with advanced stages.
Our study has important limitations. First, our results are based on the retrospective analysis. The retrospective design of this analysis further justifies the conclusion that a prospective study in the future is needed to define our findings. Second, most of the patients in this study did not have fluorodeoxyglucose positron emission tomography (FDG-PET) as comparison because it is not routinely supported by Taiwan’s health-insurance system. Third, the patients in the present study were staged based on the CT of the chest or/and EUS. The bone scan findings were not integrated into staging. Therefore, the disease staging in the preset study may be understaged.