Effectiveness of a novel low-level laser therapy protocol in managing breast cancer-related lymphedema

In this study, we investigate the effects of low-level laser therapy (LLLT) at different wavelengths on lymphedema to further determine the appropriate protocol and effectiveness of LLLT in patients with breast cancer-related lymphedema (BCRL). A randomized controlled trial was conducted involving 46 patients with BCRL. Participants were assigned to receive 904 nm LLLT, 650 nm LLLT, or sham treatment. ICG lymphography was used to assess dermal backflow as a marker of lymphatic dysfunction. Ultrasonography was used to assess subcutaneous thickness and tissue mechanical properties; shear wave velocity (SWV), with higher values indicating greater tissue stiffness, was measured using shear wave elastography. Extracellular fluid volume and local tissue water content were evaluated using multifrequency bioelectrical impedance analysis (MFBIA) and tissue dielectric constant (TDC), respectively. No significant between-group differences were observed in ICG lymphography, MFBIA, or TDC outcomes. For ultrasonographic outcomes, the overall between-group difference in the change in upper-lateral SWV ratio was significant (p = 0.029), and Bonferroni-adjusted post-hoc analysis showed a greater reduction in Group A (904 nm) than in Group B (650 nm) (adjusted p = 0.026). Within Group A, SWV ratios decreased significantly at the lower-lateral site and at the LLLT treatment site. These site-specific findings were not accompanied by measurable changes in lymphatic transport or fluid-related outcomes. Adding 904 nm-650 nm LLLT to conventional decongestive therapy did not produce significant additional effects on extracellular fluid-related or lymphatic functional outcomes. Site-specific reductions in SWV observed with 904 nm LLLT suggest a potential wavelength-dependent effect on local tissue mechanical properties; however, these findings are limited and should be considered exploratory. Larger adequately powered studies with prespecified primary outcomes and longer follow-up are required.