Early metastasis is a hallmark of small cell lung cancer (SCLC). However, the mechanisms
and resulting patterns of SCLC dissemination are unclear. Our aim was thus to investigate
the organ specificity and timing of blood-borne metastases in a comprehensive large
cohort of SCLC patients.In this retrospective non-interventional cross-sectional study
of 1009 Caucasian SCLC patients, we investigated the correlation between the distinct
locations of the primary tumor and metastatic sites.The onset of bone (p < 0.001),
brain (p < 0.001), and pericardial (p = 0.02) metastases were late events, whereas
adrenal gland (p = 0.005) and liver (p < 0.001) metastases occurred earlier. No significant
difference was found in the distribution of early versus late metastases when comparing
central and peripheral primary tumors. Patients with bone metastases had a higher
than expected likelihood of having liver metastases, while brain metastases tended
to appear together with adrenal gland metastases. Pleural and both lung and pericardial
metastases also tended to co-metastasize together more frequently than expected if
metastatic events occurred independently. Notably, patients with central primary tumors
had decreased median overall survival (OS) compared to those with peripheral tumors,
although this tendency does not appear to be significant (p = 0.072).Our results are
suggestive for particular site- and sequence-specific metastasis patterns in human
SCLC. SCLC bone metastases tend to appear together with liver metastases, while brain
metastases occur together with adrenal gland metastases. Better understanding of metastasis
distribution patterns might help to improve the diagnosis and therapeutic decision-making
in SCLC patients.
