To the Editor:
We would like to congratulate Dr. Stein and his coauthors on the results they have demonstrated from a large number of patients with early esophageal carcinoma.1 The conclusion of this work, that patients with pT1 squamous cell carcinoma (SCC) of the esophagus have worse prognoses than similar patients with pT1 adenocarcinoma (AC), corroborates the findings of other authors. However, the justification set forward by the authors for the difference in prognosis, that SCC metastasizes into the regional lymph nodes (LN) earlier than AC, cannot be derived from data presented in the study.
When the data from this study are analyzed, the following points indicate that the basis of the divergent prognostic courses of AC and SCC is multifactorial and not due to earlier LN metastasis of SCC:
The authors state that the 30-day mortality rates do not vary significantly between the 2 histologic types. However, when considering the 2 survival curves of patients with SCC and AC, despite the fact that these depictions do not contain enough data for an interpretation,2 marked differences in hospital mortality rates (corresponding to 90-day mortality rates) are easily identified. The 90-day mortality rate is approximately 2% for patients with AC and approximately 9% for those with SCC. This distinction could be secondary to the higher preoperative risks of patients with SCC compared with those with AC.3 Additionally, the more extensive intervention required for patients with SCC compared with that for patients with AC could also be the basis of higher postoperative mortality rates.
Almost double the number of AC patients had mucosal-limited carcinoma as SCC patients (36.5% vs. 18.7%). Mucosal-limited carcinoma very seldom leads to LN metastasis, regardless of histologic type. A higher rate of pN1 cases then follows a higher rate of submucosal-invading carcinomas in the pT1 SCC group compared with the pT1 AC group. Since LN metastasis is one of the most crucial factors affecting prognosis, it is inevitable that the prognosis of these more advanced pT1 SCC patients is worse than that for AC patients.
Recent studies that subclassify submucosal-invading carcinomas into thirds based on depth of penetration show a gradual increase in LN metastases occurring from sm1 through sm3 tumors.4,5 When stage-adjusted comparisons are made for submucosal subclassification, the rate of LN metastasis is not significantly different between AC and SCC.5 Increased proportions of sm3 carcinomas in SCCs compared with ACs may also play a role. These have been demonstrated with comparison of submucosal-invading carcinomas in these authors’ patient cohorts, and were not investigated in the Stein et al study patients.1
The prognostic distinction could also be conditional on the different magnitudes of lymphadenectomy performed for the differing histologic types of disease. The more extensive lymphadenectomy associated with transthoracic esophagectomy (performed more often for cases of SCC) identifies more cases of LN metastasis than that of the transhiatal approach more often used in cases of AC.
Causes of death for the 2 patient groups were not mentioned. The SCC group, however, had more secondary carcinoma than the AC group. The prognosis could be worse due to these secondary tumors.
In summary, it appears that the poorer prognoses of the pT1 SCC patients compared with the pT1 AC patients presented by Stein et al1 are not secondary to earlier LN metastasis but instead are due to: a 4-fold higher postoperative mortality, doubled incidence of submucosal-invading carcinoma, increased presence of secondary carcinoma, and increased identification of LN metastases in SCC patients secondary to the more extensive lymphadenectomy performed.
Elfriede Bollschweiler, MD, PhD
Arnulf H. Hölscher, MD
Department of Surgery
University of Cologne
Cologne, Germany
elfriede.bollschweiler@uk-koeln.de
REFERENCES
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