Effects of photobiomodulation therapy on upper limb lymphedema secondary to breast cancer: a systematic review and meta-analysis

Background Breast cancer–related lymphedema (BCRL) is a common complication that impairs function and quality of life. The effectiveness of photobiomodulation (PBM) therapy remains unclear, necessitating a systematic review and meta-analysis. Methods This review followed the PRISMA guidelines and was registered in PROSPERO (CRD420261296197). PubMed, CENTRAL, and Embase were systematically searched for randomized controlled trials (RCTs) evaluating PBM therapy for BCRL up to January 20, 2026. Outcomes of interest included upper limb volume, circumference, grip strength, and pain. Pooled effects were synthesized using appropriate meta-analytic models and reported as mean differences with 95% confidence intervals. Risk of bias, methodological quality, and certainty of evidence were assessed using RoB 2, the PEDro scale, and GRADE, respectively. Results Nine RCTs involving 312 participants with BCRL were included. Compared with control conditions, PBM therapy resulted in significant reductions in affected limb volume (SMD = −0.78, 95% CI −1.03 to −0.54; I² = 22%) and limb circumference (MD = −3.61 cm, 95% CI −4.85 to −2.38; I² = 44%). Functional outcomes also improved, with increased grip strength (MD = 1.72 kg, 95% CI 1.07 to 2.37; I² = 14%) and reduced pain intensity (MD = −0.29, 95% CI −0.52 to −0.05; I² = 0%). Overall risk of bias was low to moderate, with some concerns about allocation concealment; evidence certainty was mostly moderate by GRADE. Conclusions PBM therapy is associated with significant improvements in limb volume, circumference, grip strength, and pain in patients with BCRL. Despite these favorable findings, the overall certainty of evidence is moderate, and safety conclusions are limited by sparse adverse-event reporting. Larger, well-designed RCTs are needed to confirm efficacy and optimize treatment parameters.