Prognostic selection and long-term survival analysis to assess overdiagnosis risk in lung cancer screening randomized...

Overdiagnosis in low-dose computed tomography randomized screening trials varies from 0 to 67%. The National Lung Screening Trial (extended follow-up) and ITALUNG (Italian Lung Cancer Screening Trial) have reported cumulative incidence estimates at long-term follow-up showing low or no overdiagnosis. The Danish Lung Cancer Screening Trial attributed the high overdiagnosis estimate to a likely selection for risk of the active arm. Here, we applied a method already used in benefit and overdiagnosis assessments to compute the long-term survival rates in the ITALUNG arms in order to confirm incidence-excess method assessment.

Subjects in the active arm were invited for four screening rounds, while controls were in usual care. Follow-up was extended to 11.3 years. Kaplan-Meyer 5- and 10-year survivals of "resected and early" (stage I or II and resected) and "unresected or late" (stage III or IV or not resected or unclassified) lung cancer cases were compared between arms.

The updated ITALUNG control arm cumulative incidence rate was lower than in the active arm, but this was not statistically significant (RR: 0.89; 95% CI: 0.67-1.18). A compensatory drop of late cases was observed after baseline screening. The proportion of "resected and early" cases was 38% and 19%, in the active and control arms, respectively. The 10-year survival rates were 64% and 60% in the active and control arms, respectively (p = 0.689). The five-year survival rates for "unresected or late" cases were 10% and 7% in the active and control arms, respectively (p = 0.679).

This long-term survival analysis, by prognostic categories, concluded against the long-term risk of overdiagnosis and contributed to revealing how screening works.