Analysis of Recurrence Sites in Esophageal Squamous Cell Carcinoma after Neoadjuvant Chemoradiation with Elective Nodal Irradiation: Insights for Radiation Field Optimization.

Background: The optimal radiation field for neoadjuvant chemoradiotherapy (NCRT) in patients with esophageal squamous cell carcinoma (ESCC) remains debated. This study investigated recurrence patterns following NCRT with elective nodal irradiation (ENI), specifically comparing the recurrence sites relative with radiation treatment fields.

Patients and methods: We retrospectively analyzed 255 patients with ESCC treated with NCRT with ENI. Radiation fields included supraclavicular or celiac lymph nodes on the basis of tumor location. An imaginary involved field irradiation (IFI) was defined to cover the gross tumor with margins. Recurrence sites were classified as within IFI field, between IFI and ENI margins, or outside ENI field.

Results: With a median follow-up of 42.2 months, 65 patients (25.5%) experienced recurrence, and 66.2% of these recurrences occurred with distant metastasis. Among 22 patients with isolated local recurrence (LR), 12 (54.5%) occurred within IFI field and 6 (27.3%) between IFI and ENI margins. The rate of isolated LR between IFI and ENI margins was 0% in upper, 6.2% in middle, and 3.9% in lower thoracic tumors. Among 120 patients with pathologic complete response (pCR), isolated LR occurred in 4 (3.3%), with only 1 case between IFI and ENI margins. In 135 patients with non-pCR, isolated LR was observed in 18 (13.3%), with only 5 between IFI and ENI margins.

Conclusions: Two-thirds of the recurrences occurred with distant metastasis and over half of isolated locoregional recurrences occurred within the IFI field. This highlights the need to reassess extended radiation field and to consider individualized radiation strategies on the basis of tumor location and pathologic response.