Editor's Note: From September 22nd to 24th, 2024, the 20th International Society for Diseases of the Esophagus (ISDE) conference was grandly held in Edinburgh, Scotland. Dr. Filipa Fonseca from the Lisbon Oncology Research Center presented a study on the modified Siewert classification for adenocarcinoma of the esophagogastric junction (EGJ) at the Late-Breaking Oral Abstract session (Abstract No.: LB-OA02.07), which sparked extensive discussion and interest. Oncology Frontier conducted an exclusive interview with Prof. Fonseca at the conference venue regarding this classification method.

Oncology Frontier: Your revised approach to the esophagogastric junction with a modified Siewert classification aims to address specific challenges in classification. Can you elaborate on the main limitations of the original Siewert classification and how your modifications address these issues?

Dr. Filipa Fonseca：As you are aware, the Siewert classification was initially proposed in 1987, and it relies on the definition of the EG junction, but also on the tumor epicenter. And the definition of the tumor epicenter can be subjective and also inconsistent. So this prompts us to really, I think that we are talking about the same tumors when we talk, for example, about the Siewert tumor. That can be just a Siewert Ⅱ, but also has its esophageal involvement and gastric involvement. So really, Siewert Ⅱ tumors can be super different, and the Siewert classification does not really have an implication of the resection margins and also on the lymph node dissection extension.

Oncology Frontier: In your modified Siewert classification, what are the key criteria that differentiate the revised classification from the original one? How do you anticipate these changes will impact clinical decision-making and treatment outcomes for patients with esophagogastric junction tumors?

Our modified Siewert classification relies on three endoscopic measurements. The endoscopic EG junction, as is classified in the Japanese guidelines, but also on the proximal and distal limits.So we have a classification that truly reflects the full extension of the tumor and its relationship with the EGJ junction and not only the epicenter. So we think that these classifications really manifest in the choice of surgery and the extension of the resection, but also on the definition of the lymph node dissection that should be done in that particular case.

Oncology Frontier: How does your modified Siewert classification integrate with current treatment guidelines and multidisciplinary approaches for managing esophagogastric junction tumors? Are there specific cases or scenarios where this revised classification offers significant advantages over existing classifications?

Dr. Filipa Fonseca：So, yes, this classification could be integrated in the current guidelines, because actually it’s a reflection of the full extension of the tumor.

So it will reflect on the choice of resection extension and also on the lymph node dissection extension. So really its implication on the choice that everyone, every surgeon makes. And its future implications will be on the R0 resection margins rates, and also in the local regional metastasis rate, and also on the overall survival of these patients. And you can see our work and our poster with more detailed information about the specific examples and which this classification changed our approach, and hopefully in the future, your approach too.