## 3 Results  
A total of 170 patients (83 women and 87 men; median age: 31 years ranging from 18 to 61 years) were enrolled in the study: 90 patients were treated with PBM (the treatment group), and the remaining 80 patients did not receive PBM (the control group). At baseline, the patients' LII index in the control group ranged from 3.3 to 13.2 mm (median 7.65 mm,IQR: 6.55 mm; 9.20 mm), whereas in the PBM group, it ranged from 3.5 to 13.2 mm (median 7.9 mm, IQR: 6.4 mm; 9.4 mm), with no statistically significant difference between the two groups. The complete demographic and clinical characteristics are reported in Table 1.  
At T1, the median crowding resolution rate was significantly higher in the PBM group (median: 0.33 mm/week, IQR: 0.30; 0.38) than in the control group (median: 0.21 mm/week; IQR: 0.18; 0.23) (\(p\) < 0.001, effect size: 2.74) (Figure 2(a)). A subgroup analysis was also performed to evaluate the differences between the control and intervention groups at different ages. The statistically significant difference between the control and intervention group was confirmed in both comparisons (\(p\) < 0.001 for patients aged <30 years and for patients aged \(\geq\)30 years), while there was no statistically significant difference in the patients treated with PBM aged <30 and \(\geq\)30 years (Figure 2(b)).  
A statistically significant difference, that is, the log-rank test difference between the two curves: \(p\) < 0.001, emerged between the PBM (median: 160 days, 95% CI: 148; 172) and the CTL groups (median: 245; 95% CI: 217; 273) (Figure 3(a)). When the same analysis was repeated according to the age of the patients, the log-rank test confirmed the difference between the PBM and control groups, whereas there was no difference between the patients <30 and \(\geq\)30 years in either group.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Total** & **Control** & **PBM** & \(p\)**-Value \({}^{*}\)** \\ \hline No. of patients & 170 & 80 (47.1\%) & 90 (52.9\%) & \\ \hline Age (year), median (IQR) & 31 (25; 38) & 31 (24.5; 37) & 33 (25; 38) & 0.475 \\ \hline Age range & & & & \\ \hline \textless{}30 years & 73 (42.9\%) & 35 (43.7\%) & 38 (42.2\%) & 0.877 \\ \hline \textgreater{}30 years & 97 (57.1\%) & 45 (56.3\%) & 52 (57.8\%) & \\ \hline Gender, n (\%) & & & & \\ \hline Female & 83 (48.8\%) & 41 (51.3\%) & 42 (46.7\%) & 0.645 \\ \hline Male & 87 (51.2\%) & 39 (48.7\%) & 48 (53.3\%) & \\ \hline LII0 (mm), median (IQR) & 7.8 (6.5; 9.4) & 7.65 (6.55; 9.20) & 7.9 (6.4; 9.4) & 0.677 \\ \hline LIII (mm), median (IQR) & 0.21 (0.14; 0.40) & 0.20 (0.15; 0.38) & 0.23 (0.12; 0.4) & 0.955 \\ \hline \hline \end{tabular} \({}^{*}\)\(p\)-value for comparison of group median by Mann–Whitney U test or difference in proportion by Fisher exact test as appropriate; IQR: (25 th percentile; 75 th percentile).  
\end{table}
Table 1: Basic demographic and clinical characteristics of the sample.  
Figure 3: Box Plot. (**a**) The alignment rate in control and PBM groups; (**b**) subgroup analysis by age range: the alignment rate in control and PBM groups related to age (age <30 years, age \(\geq\)30 years).  
The multivariate analysis showed that the hazard of success increased rapidly in the PBM treatment (HR: 25.69, SE: 6.90, \(p\) < 0.001), while the hazard decreased when the LII0 increased (Table 2).