KEY POINTS
- This single-institution retrospective study included 722 breast cancer patients treated with surgery and postoperative radiotherapy from 2018–2020. Median follow-up was 30 months; 283 patients (39.2%) underwent axillary lymph-node dissection, and radiotherapy was delivered predominantly with VMAT (91.3%) and hypofractionation (90.0%).
- Clinically relevant breast cancer-related lymphedema was defined strictly as new upper-limb International Society of Lymphology stage ≥2 disease. Overall, 124 patients developed some lymphedema, while 91 of 722 (12.6%) met the primary endpoint, at a median of 13.6 months after RT.
- Investigators retrospectively contoured the axillary-lateral thoracic junction (ALTJ), a venolymphatic region near superior axillary level I proposed as particularly relevant to arm lymphatic drainage. Mean ALTJ volume was 17.4±6.7 cm³, and multiple dose-volume parameters were evaluated.
- ALTJ V35Gy emerged as the strongest candidate dosimetric parameter. 369 patients (51.1%) had >50% of the ALTJ receiving ≥35 Gy, while 353 had ≤50%. In multivariable analysis, ALTJ V35Gy >50% was associated with approximately threefold higher lymphedema risk: HR 3.07 (95% CI 1.47–6.42; p=0.003).
- By contrast, simply classifying treatment as extensive regional nodal irradiation did not independently predict lymphedema: HR 1.31 (95% CI 0.73–2.34; p=0.363). This supports the idea that the actual dose received by a specific lymphatic region may be more informative than the nominal treatment-field label.
- Replacing regional nodal irradiation status with ALTJ V35Gy improved model fit substantially: AIC decreased from 1029.89 to 1021.14 (ΔAIC 8.64). Discrimination improved only slightly, however, with C-index 0.753 vs 0.749 and 24-month AUC 80.6% vs 78.9% (p=0.096), so the improvement in predictive accuracy was not statistically significant.
- The study was retrospective, lacked systematic patient-reported outcomes and preoperative limb-volume measurements, and excluded patients with progression within the first year. The authors therefore frame ALTJ sparing as a potential planning strategy requiring prospective validation rather than a new mandatory constraint.
CLINICAL TAKEAWAY
This paper makes a clinically useful distinction: “regional nodal irradiation” may be too crude a variable for predicting lymphedema; the actual dose to the lymphatic anatomy may matter more. ALTJ V35Gy >50% is a compelling candidate constraint, but prospective confirmation is needed before routine axillary planning is changed around it.