Patterns of Recurrence After D2 Radical Surgery for Gastric Cancer: Implications for Postoperative Radiation Therapy.

Purpose: We evaluated the role of adjuvant radiation therapy after D2 lymphadenectomy for gastric cancer (GC), identified patients most likely to benefit from postoperative radiation therapy, and defined the optimal target volume for adjuvant radiation therapy by analyzing recurrence patterns.

Methods and materials: We retrospectively analyzed 1169 patients with stage I to III GC who underwent D2 surgery, of whom 225 experienced recurrence. Both overall and regional recurrences were examined, with regional recurrence patterns categorized by tumor site. Particular emphasis was placed on the vertical distribution of recurrences in lymph nodes at station no. 16. Risk factors for locoregional failure (LRF) were identified by using multivariate logistic regression. A predictive nomogram for LRF was developed and validated by using discrimination (area under the curve of a receiver operating characteristic curve) and calibration (calibration curve with bootstrap resampling).

Results: The predominant pattern of single-site recurrence was peritoneal failure (29.8%), followed by distant metastasis (23.1%) and locoregional failure (20.0%). High-risk lymph node stations for regional recurrence (>10%) included nos. 7, 8, 9, 11p, 12, 13, 16a, and 16b. Although regional recurrence patterns varied by tumor location, station no. 16 consistently demonstrated the highest recurrence rate. Recurrent lymph nodes at station no. 16 exhibited a normal distribution, with about 90% estimated as being located between 6.1 cm below and 5.0 cm above the lower edge of the left renal vein. Multivariate analysis identified pathologic T category (3-4 vs 1-2) and lymph node ratio (>25% vs ≤25%) as independent risk factors for LRF. A predictive nomogram incorporating these factors was developed that achieved an area under the curve of 0.79, indicating good discrimination ability.

Conclusions: This study of recurrence patterns and risk factors for LRF in patients with GC after D2 lymphadenectomy suggests a subpopulation who may benefit from adjuvant radiation therapy and offers insights for target volume definition.