Discussion
osteosarcoma, tumor
TUMOR, METASTASIS, RECURRENCE, SECOND PRIMARY CANCER, LUNG METASTASIS, BRAIN METASTASES, DISEASE, OSTEOSARCOMA, LUNG METASTASES, TUMOR PROGRESSION, LATE EFFECT
To the best of our knowledge, this is the first study of attempting to describe the epidemiology, and identify risk factors and prognostic factors for pediatric and young adulthood osteosarcoma patients with SLM, by using the SEER database. The result turned out that, between year 2010 and 2019, approximately 14.1% of all pediatric and young adulthood osteosarcoma patients developed a SLM at diagnosis. The rate was lower than that of entire osteosarcoma patients with SLM, mainly because of a relatively higher proportion of SLM in the elder patients [A few previous studies with SEER database reported clinical risk factors for lung metastases in entire osteosarcoma patients, including advanced age, gender, large tumor size, higher N stage, advanced tumor grade, presence of bone and/or brain metastases, and axial location [For nonmetastatic osteosarcoma patients, lung metastasis was also the most common site in the later stage of disease, with a rate of approximately 40–55% [Nigris and colleagues demonstrated that the growth and development of osteosarcoma, as well as the metastasis development, depend on a tightly regulated and balanced angiogenesis [Some inflammatory cytokines may also get involved in the tumor progression, recurrence and metastasis of osteosarcoma [The most common and valuable method to screen lung metastasis is chest computed tomography (CT) [This study found a dismal CSS in pediatric and young adulthood osteosarcoma patients with SLM, with a median CSS of only 25 months, which was similar with previous studies [Approximately 12.2% of patients received radiotherapy, but this treatment also demonstrated no impact on survival. A concern should be acknowledged, radiotherapy in young patients may cause second primary cancer as a late effect [There are some limitations in this study. First, the nature of retrospective study might lead to data bias. Second, though we select patients from the SEER database, the sample size of this study is still limited because of the rare incidence of osteosarcoma. Besides, we did not perform external validation. Hence, more samples are warranted to identify the predictive power of the nomogram. Third, the information available from SEER database are limited, many associated risk factors mentioned above are not provided. Further studies should include more factors to construct a more powerful model. Last, limited to the follow-up time, the long-term survival for pediatric and young adulthood osteosarcoma patients with SLM could not be estimated accurately. This should be investigated in the future studies.