Participant characteristics and baseline QoL

Table 1 presents the demographic and clinicopathologic characteristics of 619 HNSCC patients and their baseline QoL scores. Among the participants, 458 (73.99%) were men, and 161 (26.01%) were women. Current smoking was most common among patients with laryngeal cancer (67.6%, 102/151), followed by those with oral cavity cancer (50.6%, 160/316) and pharyngeal cancer (37.5%, 138/368). The mean age of participants was 60.88 ± 11.37 years, with a median age of 60. Patients aged ≤ 60 years had a baseline mean QoL score of 51.43 (95% CI: 50.17, 52.69), while those aged > 60 years had a lower mean QoL score of 48.54 (95% CI: 47.22, 49.85) at baseline (P = 0.001). Men had much better QoL at baseline than women (P < 0.0001). Regarding cancer subsite, most patients had tumors in the pharynx (46.20%), followed by the oral cavity (36.51%) and the larynx (17.29%). The mean QoL score at baseline was highest in patients with pharyngeal cancer, 51.68 (95% CI: 50.32, 53.04), following oral cavity cancer, 49.27 (95% CI: 47.83, 50.70) and lowest in those with laryngeal cancer, 47.42 (95% CI: 45.12, 49.72) (P = 0.002) (Table 1).

Table 1 Demographic and clinicopathologic characteristics of 619 head and neck cancer patientsQoL by demographic and clinical features

The stage of cancer at diagnosis also influenced the QoL score at baseline, with patients diagnosed at earlier stages (In situ and stage I) having higher baseline QoL scores compared to those with more advanced stages. Specifically, patients with stage IV cancer (57.03% of the cohort) had a mean QoL score of 54.81 (95% CI: 52.31, 57.32), significantly lower than those diagnosed in earlier stages, who had a mean of 60 (95% CI: 54.97, 65.02), with a p-value of 0.030. The analysis also revealed that BMI had an impact on QoL, with underweight patients reporting the lowest QoL score at baseline, 44.30(95% CI: 38.56, 50.03), while overweight and obese patients had higher QoL scores 51.44 (95% CI: 49.97, 52.91) and 50.39 (95% CI: 48.70, 52.08), which was statistically significant (P = 0.010). Additionally, comorbidities were associated with QoL, with patients having no comorbidities reporting the highest mean QoL score, 54.02(95% CI: 52.35, 55.69), while those with severe comorbidities had the lowest, 43.85 (95% CI: 40.09, 47.61), with a significant p-value of < 0.0001. Regarding treatment modalities, chemoradiation therapy was the most common treatment (44.26%) and was associated with the highest baseline QoL score of 51.03 (95% CI: 49.59, 52.46). This was followed by surgery alone (25.53%) with a QoL score of 50.68 (95% CI: 48.97, 52.38), and radiation therapy alone (6.95%) with a score of 50.47 (95% CI: 46.84, 54.10). Patients who received surgery plus adjuvant chemoradiation therapy (12.60%) had a QoL score of 46.93 (95% CI: 45.38, 50.67), and those who underwent surgery plus adjuvant radiation therapy (10.66%) also had a QoL score of 46.93 (95% CI: 44.38, 49.48). Differences in QoL scores were also observed based on smoking status, with current smokers reporting the lowest QoL scores, 46.88 (95% CI: 45.39, 48.37), and former smokers having higher scores, 51.42(95% CI: 49.89, 52.94, following that never smokers, 53.16 (95% CI: 51.55, 54.78) (P < 0.0001). Alcohol consumption was similarly associated with QoL, with never drinkers having a mean QoL score of 49.01 (95% CI: 45.27, 52.75), significantly lower than current drinkers, 51.47(95% CI: 50.30, 52.65) and former drinkers, 47.93(95% CI: 46.37, 49.48), P = 0.001 (Table 1).

QoL over time

Significant differences over time were observed in several domains over the course of 5 years (Fig. 1). The physical functioning, role limitations due to emotional problems, and pain domains showed substantial improvements over time (P = 0.0014, P < 0.0001, and P < 0.0001, respectively). In contrast, social functioning consistently worsened across follow-up (P < 0.0001), indicating a decline in patients’ social health. Energy/fatigue and emotional well-being remained relatively stable, with non-significant changes at several time points (e.g., P = 0.8648 for emotional well-being). Overall, the figure highlights the significant temporal shifts towards improvement in several domains of QoL.

Fig. 1

The distribution and trend of various health scores (Total QoL, PF, RP, P, RE, EF, WE, Sf_social, and GH) across six time points (0–5). [physical functioning (PF), role limitations due to physical health (RP), role limitations due to emotional problems (RE), energy/fatigue (EF), emotional well-being (WE), social functioning (SF-Social), pain (P), and general health (GH)]. In the boxplots, the central square line represents the median QoL score for each group, while the diamond represents the mean. In some cases, both a line and a diamond are displayed when the mean and median differ

Table 2 illustrates the results of a multiple linear regression analysis assessing the QoL in HNSCC patients over time, stratified by cancer subsite. For the total QoL score, significant early improvements were observed, particularly at the 1-year post-diagnosis [adjusted β: 2.86 (95% CI: 1.56, 4.16)]. Patients with pharyngeal cancer showed the greatest increase in QoL score [adjusted β: 3.56 (95% CI: 1.69, 5.43)], followed by those with oral cavity cancer [adjusted β: 2.56 (95% CI: 0.52, 4.60)]. Laryngeal cancer patients, however, showed no meaningful changes across follow-up [e.g., 1-year adjusted β: 0.93 (95% CI: −2.36, 4.24)], indicating a lack of improvement in overall QoL for this subgroup. (Table 2).

Table 2 Multiple linear regression of quality of life and its components over time by HNC subsites

Physical functioning improved most clearly among pharyngeal cancer patients, particularly at the 5-year follow-up [adjusted β: 2.04 (95% CI: 1.09, 2.98)], while oral cavity and laryngeal cancer patients showed inconsistent patterns. Role limitations due to physical health also improved significantly over time, especially for pharyngeal cancer patients (p < 0.0001), whereas emotional well-being tended to worsen, with the greatest decline at 1 year [adjusted β: −1.85 (95% CI: −3.35, −0.34)]. Energy/fatigue showed little change overall, though laryngeal cancer patients exhibited borderline worsening at 3 years [adjusted β: −1.63 (95% CI: −3.25, −0.01)] (Table 2).

Further, the role limitations due to physical health and emotional well-being domains also reflected varying improvements across subsites. Pharyngeal cancer patients showed significant improvements in role limitation due to physical health across all follow-up time points, with adjusted β values ranging from 3.66 to 10.47 for HNSCC combined (p < 0.0001), particularly in pharyngeal cancer patients. Similarly, patients with HNSCC showed consistently worsened emotional well-being, with the lowest improvement at 1-year follow-up [adjusted β: −1.85 (95% CI: −3.35, −0.34)]. Regarding energy/fatigue, patients with any HNSCC showed minimal, non-significant energy levels and fatigue improvements across all follow-up periods. Notably, at the 3-year follow-up, patients with laryngeal cancer exhibited a borderline worsening in energy/fatigue, as indicated by an adjusted β of −1.63 (95% CI: −3.25, −0.01) (Table 2).

For role limitations due to emotional problems, significant improvements were observed in the oral cavity and pharyngeal cancer patients, particularly at the 1-year follow-up, with adjusted β values of 6.88 (95% CI: 1.50, 12.25) and 7.93 (95% CI: 3.54, 12.33), respectively, indicating a reduction in emotional distress. However, laryngeal cancer patients showed more variable results, with initial improvement at 1 year (β = 8.76, 95% CI: 1.25, 16.27), but less consistency at later follow-ups, as seen in the 5-year data. All HNSCC patients showed consistent deterioration in Social functioning over time, with the most notable changes observed at the 1-year follow-up [adjusted β: −5.15 (95% CI: −8.4, −2.26)], indicating a substantial decline in Social functioning. Mainly, pharyngeal cancer patients exhibited significantly fewer improvements, particularly at the 1-year follow-up [adjusted β: −5.76 (95% CI: −9.93, −1.59)]. Laryngeal and oral cavity cancer patients showed no significant changes at follow-ups (Table 2).

Pain decreased steadily after diagnosis, with all tumor subsites showing improvement at 1 year [adjusted β: 3.08 (95% CI: 0.69, 5.47)] and sustained relief at 2 years [adjusted β: 2.68 (95% CI: 1.37, 4.00)]. Nonetheless, pain remained an ongoing issue for many patients, and laryngeal cancer patients in particular did not demonstrate consistent improvement [e.g., 1-year β: 3.92 (95% CI: −1.74, 9.59)]. Finally, general health improved over time in all subsites, most notably at the 1-year follow-up [adjusted β: 6.43 (95% CI: 3.71, 9.14)] and remained higher at 5 years [adjusted β: 1.56 (95% CI: 0.60, 2.51)], with pharyngeal cancer patients experiencing the greatest sustained gains.

Post-diagnosis smoking cessation impact on QoL

Never smokers and quitting smoking were associated with improved QoL (Table 3; mean QOL scores at baseline, 1 year, and 2 years after diagnosis). For the Total QoL score, patients who had never smoked showed a significant improvement in QoL over time, with mean scores increasing from 53.11 at baseline to 57.51 at 1 year (P = 0.01) and further improving to 59.29 at 2 years (P < 0.0001). Quitters increased from 48.09 at baseline to 50.35 at 1 year (P = 0.11) and 51.42 at 2 years (P = 0.04); however, these improvements were less pronounced compared to never-smokers. Continued smokers showed no significant changes in QoL, with scores fluctuating slightly over time (baseline: 45.18, 1 year: 46.57, 2 years: 46.34). Intermittent smokers displayed similar trends to those of continued smokers, with a slight increase in QoL from baseline (53.06) to 1 year (53.85), although these changes were not statistically significant. Significant differences in QoL scores across post-diagnosis smoking groups were observed at all follow-up periods (P < 0.0001), indicating that smoking status is a key factor influencing QoL in these patients (Fig. 2).

Table 3 Mean score of quality of life and its components at baseline, 1 year and 2 years of follow up by smoking status after diagnosisFig. 2

The distribution and trend of overall quality of life score by smoking status after diagnosis. In the boxplots, the central square line represents the median QoL score for each group, while the diamond represents the mean. In some cases, both a line and a diamond are displayed when the mean and median differ

In oral cavity cancer patients, never smokers showed significant improvements in QoL, with an increase from 52.40 at baseline to 56.16 at 1 year, 55.50 (P = 0.01), and 2 years (P < 0.0001). In contrast, quitters exhibited moderate increases in QoL over time, with their scores rising from 50.32 at baseline to 54.47 at the 2-year follow-up (P = 0.04). However, patients with continued smoking demonstrated minimal change in QoL, with scores remaining relatively stable and insignificant across follow-up periods. For pharyngeal cancer, never smokers also experienced significant improvements, with QoL increasing from 53.56 at baseline to 59.24 (P = 0.01) at 1 year and 61.51 at 2 years (P < 0.0001). Like the oral cavity group, quitters showed positive changes, although the improvement was less pronounced, with their QoL scores increasing from 49 at baseline to 54.98 at the 2-year follow-up (P = 0.02). Conversely, continued smokers and intermittent smokers exhibited minimal or no significant changes in QoL, suggesting persistent challenges related to smoking status. In the laryngeal cancer patients, never smokers demonstrated the least variation in QoL over time, with scores increasing slightly and insignificant from 47.48 at baseline to 49.51 at 2 years (P = 0.55) for continued smokers and 54.17 at baseline to 56.32 at 2 years (P = 0.28) for intermittent smokers (Table 3) (Supplement Table 1).

Changes in voice and dry mouth symptoms across smoking behavior subgroups

Longitudinal analysis revealed distinct patterns in patient-reported outcomes related to voice function and dry mouth across smoking behavior subgroups following cancer diagnosis (Fig. 3). Mean scores for voice volume and voice clarity improved over time among head and neck cancer patients, with notable differences based on post-diagnosis smoking behavior. Participants who remained former smokers or quit smoking after diagnosis consistently exhibited greater improvements in both voice volume and clarity compared to those who continued smoking. Statistically significant linear trends were observed among those who continued smoking, quit smoking, or exhibited intermittent smoking behavior, indicating measurable changes in vocal function over the five-year follow-up period. In contrast, mean dry mouth scores did not show significant longitudinal trends across any smoking behavior subgroup. The patterns for dry mouth were more variable, with no consistent direction of change, suggesting that xerostomia symptoms may be less sensitive to changes in smoking behavior post-diagnosis.

Fig. 3

Trends in voice clarity, dry mouth, and voice volume over time by post-diagnosis smoking behavior