How to confront the high prevalence of pulmonary micro nodules (PMNs) in osteosarcoma patients?

Pulmonary metastasis was a negative factor of osteosarcoma prognosis. However, there is no universal criteria to confirm pulmonary metastasis at pulmonary micro nodule (PMN, Dmax ≤ 5 mm) stage other than pathology. We aimed to identify prevalence of PMNs, determine prognosis of osteosarcoma with PMNs, and analyze risk factors related to PMN progression.

We retrospectively reviewed 425 consecutive osteosarcoma patients. According to dynamic change in size and number of PMNs, patients were divided into PMN progression and non-progression group. Demographic data, initial laboratory data, radiological features, and oncological evaluations were analyzed. Cox regression was used to identify risk factors for PMN progression. Overall survival rate was measured and analyzed with Kaplan-Meier method. Differences with p < 0.05 were considered significant.

PMNs were found in 74% (315/425) osteosarcoma patients, half of whom (157/315) suffering PMN progression. Overall survival rate was 70.2%, while survival rates for PMN progression group and non-progression group were 53.40% and 87.40%, respectively. Clinical risk factors for PMN progression in certain patients included blood vessel invasion, extrapulmonary metastases, low tumour cell necrosis rate, and large tumour size. Radiologic risk factors included greatest diameter, distance to pleura, CT value, solid components, and smooth border.

PMN is quite common in osteosarcoma patients. PMN progression is related to both certain clinical and radiological factors, which could assist surgeons to determine its possibility to progress at an early stage.