RESULTS

We identified 4014 cases of invasive NSCLC as eligible for analysis. Most patients (94.9%) were Caucasian, and 55.7% were male. Approximately half of the patients lived in rural areas (48%). KCI scores were 0 (no or very low comorbidity), 1 (low comorbidity), 2 (moderate comorbidity), and ≥3 (severe comorbidity) in 46.8%, 29.1%, 10.8%, and 13.3% of the study sample, respectively.

Receiving lung cancer treatment


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The proportion of patients by stage who did not receive any treatment for lung cancer were 8.7%, 3.9%, and 19.1% for stage I, stage II, and stage III, respectively (p<0.0001). A total of 49.1% of stage IV patients did not receive any chemotherapy and 23.5% of this cohort did not receive any treatment modality (p<0.0001). Compared with the treated individuals, the untreated population had a higher proportion of patients >75 years old, diagnosed at stage IV, residing in rural areas, having higher comorbidity index scores, and more likely to live in areas of lower education levels. Of the patients with a KCI≥3%, 25.4% were untreated, compared with 16.4% of patients with KCI=0%, 15.7% with KCI=1%, and 18.2% with KCI=2 (p<0.0001) (Table 1). Across all stages, the proportion of patients with high comorbidity (KCI ≥3) was similarly distributed (15.2% in stages I–II, 12.9% in stage III, and 12% in stage IV). In multivariate analysis, older age, more advanced stage, higher comorbidity index, and residency in rural areas were significantly associated with a lower likelihood of receiving lung cancer treatment.

(To view a larger version of Table 1, click here.)

Survival analysis

In patients with KCI=0, the median OS for the untreated group was 17.7 months for stages I and II, 2.3 months for stage III, and 1.3 months for stage IV. For KCI=0 patients who received treatment, the median OS was 58.9, 16.8, and 5.8 months for stages I and II, III, and IV, respectively (Figures 2–4). In patients with KCI ≥3, the median OS for the untreated group was 6.1, 1.6, and 1.2 months for stages I and II, III, and IV, respectively. For the KCI ≥3 patients who received any treatment, the median OS was 22.9, 10.9, and 3.7 months for stages I and II, III, and IV, respectively (Figures 2–4). In multivariate Cox regression models, age, gender, stage, KCI scores, and receiving treatment were associated with survival (Table 2). In particular, higher comorbidity was independently associated with lower OS (HR=1.51 for KCI≥3 vs KCI=0; 95% CI 1.363–1.679; p<0.001).

 


 


 


Within each comorbidity index level, patients who received no therapy had worse survival than those who received any therapy (Table 3).