Background: Patients with advanced-stage lung adenocarcinoma (LADC) often develop
distant metastases in the skeletal system. Yet, the bone-specific metastasis pattern
is still controversial. We, therefore, aimed to examine how the primary tumor location
affects bone specificity and survival in LADC patients diagnosed with skeletal metastases.
Methods: In total, 209 bone-metastatic Caucasian LADC patients from two thoracic centers
were included in this study. Focusing on the specific location of primary tumors and
bone metastatic sites, clinicopathological variables were included in a common database
and analyzed retrospectively. Skeletal metastases were diagnosed according to the
contemporary diagnostic guidelines and confirmed by bone scintigraphy. Besides region-
and side-specific localization, primary tumors were also classified as central or
peripheral tumors based on their bronchoscopic visibility. Results: The most common
sites for metastasis were the spine (n = 103) and the ribs (n = 60), followed by the
pelvis (n = 36) and the femur (n = 22). Importantly, femoral (p = 0.022) and rib (p
= 0.012) metastases were more frequently associated with peripheral tumors, whereas
centrally located LADCs were associated with humeral metastases (p = 0.018). Moreover,
we deduced that left-sided tumors give rise to skull metastases more often than right-sided
primary tumors (p = 0.018). Of note, however, the localization of the primary tumor
did not significantly influence the type of affected bones. Multivariate Cox regression
analysis adjusted for clinical parameters demonstrated that central localization of
the primary tumor was an independent negative prognostic factor for overall survival
(OS). Additionally, as expected, both chemotherapy and bisphosphonate therapy conferred
a significant benefit for OS. Conclusion: The present study demonstrates unique bone-specific
metastasis patterns concerning primary tumor location. Peripherally located LADCs
are associated with rib and femoral metastases and improved survival outcomes. Our
findings might contribute to the development of individualized follow-up strategies
in bone-metastatic LADC patients and warrant further clinical investigations on a
larger sample size.
