A 20-year Follow-up of the International Early Lung Cancer Action Program (I-ELCAP)

Abstract

Background The low-dose CT (≤3 mGy) screening report of 1000 Early Lung Cancer Action Program (ELCAP) participants in 1999 led to the International ELCAP (I-ELCAP) collaboration, which enrolled 31 567 participants in annual low-dose CT screening between 1992 and 2005. In 2006, I-ELCAP investigators reported the 10-year lung cancer-specific survival of 80% for 484 participants diagnosed with a first primary lung cancer through annual screening, with a high frequency of clinical stage I lung cancer (85%). Purpose To update the cure rate by determining the 20-year lung cancer-specific survival of participants diagnosed with first primary lung cancer through annual low-dose CT screening in the expanded I-ELCAP cohort. Materials and Methods For participants enrolled in the HIPAA-compliant prospective I-ELCAP cohort between 1992 and 2022 and observed until December 30, 2022, Kaplan-Meier survival analysis was used to determine the 10- and 20-year lung cancer-specific survival of participants diagnosed with first primary lung cancer through annual low-dose CT screening. Eligible participants were aged at least 40 years and had current or former cigarette use or had never smoked but had been exposed to secondhand tobacco smoke. Results Among 89 404 I-ELCAP participants, 1257 (1.4%) were diagnosed with a first primary lung cancer (684 male, 573 female; median age, 66 years; IQR, 61-72), with a median smoking history of 43.0 pack-years (IQR, 29.0-60.0). Median follow-up duration was 105 months (IQR, 41-182). The frequency of clinical stage I at pretreatment CT was 81% (1017 of 1257). The 10-year lung cancer-specific survival of 1257 participants was 81% (95% CI: 79, 84) and the 20-year lung cancer-specific survival was 81% (95% CI: 78, 83), and it was 95% (95% CI: 91, 98) for 181 participants with pathologic T1aN0M0 lung cancer. Conclusion The 10-year lung cancer-specific survival of 80% reported in 2006 for I-ELCAP participants enrolled in annual low-dose CT screening and diagnosed with a first primary lung cancer has persisted, as shown by the updated 20-year lung cancer-specific survival for the expanded I-ELCAP cohort. © RSNA, 2023 See also the editorials by Grenier and by Sequist and Olazagasti in this issue.

Graphical abstract

Figure 1:

Kaplan-Meier curve shows lung cancer–specific survival for all 1257 participants with lung cancer and for the 181 participants undergoing resection with resulting pT1aN0M0 and tumor size of 10 mm or less in the pathology specimen.

Figure 2:

(A, B) Two annual repeat low-dose CT scans in a woman who was 60 years old at baseline enrollment in 1999. At baseline enrollment, she was currently smoking and had a 30-pack-year smoking history. No nodules were identified on baseline low-dose CT scans. On the sixth annual low-dose CT scan (B), a right lower lobe solid nodule (arrow) measuring 4.5 mm in maximum diameter was identified. The nodule could be identified in retrospect on the prior annual CT scan (arrow in A), when it measured 2.0 mm in maximum diameter. Estimated tumor volume doubling time was 161 days. Lobectomy was performed 2 months later, and diagnosis of stage 1aN0M0 moderately differentiated adenocarcinoma measuring 6.0 mm in maximum diameter was made. Expert pathologic panel review (22) of the pathologic specimen updated the diagnosis to adenocarcinoma with mixed subtype (80% acinar, 20% bronchoalveolar carcinoma components) with 5 mm of invasion.

Figure 3:

Kaplan-Meier curve shows lung cancer–specific survival for all 1257 participants with lung cancer, organized by smoking categories (participants who never smoked or who smoked less than 10 pack-years, participants who smoked 10–29 pack-years, and participants who smoked at least 30 pack-years).