Metastases with definitive pathological diagnosis but no detectable primary tumor: A surveillance epidemiology and end results‐based study

Abstract

Background This study investigates the characteristics of a special type of cancer of unknown primary site (CUP, type 2), which is a metastasis of a definite pathological diagnosis without a detectable primary site. Patients and methods Patients diagnosed between 2004 and 2014 were identified from the Surveillance Epidemiology and End Results (SEER) database. The characteristics of type 2 CUP from different sources were analyzed. For each source of type 2 CUP, tumors of the corresponding TnN0‐XM1 stage were used as controls. Results A total of 8505 patients with type 2 CUP were included in this analysis. Type 2 CUP shows an increasing trend, while type 1 shows the opposite. Type 2 CUPs have significant differences with stage IV of the same pathological primary lesion. Many characteristics influenced the prognosis of type 2 CUP patients, including marital status, age, race, sex, registration time, lymph node metastasis, surgery, chemotherapy, and radiation. Conclusion Our study suggests that identifying the source of metastasis is the key to the selection of treatment and the determination of the prognosis for CUP.

Risk factors and predictors for tumor site origin in metastatic adenocarcinoma of unknown primary site

“…Additionally, subsequent site-specific therapy would be tailored individually by referring to the protocol of the known tumor site, and these patients could benefit from this treatment model. 10 Nevertheless, there are still some shortcomings and limitations in this study. First, it was a retrospective analysis based on the SEER database, and the current determination of the origin sites by pathological examination and immunohistochemistry lacked a specific standard, which might be due to the complexity of MACUP and the future direction of prediction for the primary sites.…”

“…Hayashi et al 18 and Fizazi et al 19 conducted randomized controlled trials and found that site-specific therapy based on T A B L E 5 Logistic regression analysis of the risk factors for the source site of respiratory system in MACUP patients microarray profiling could not improve the survival, meanwhile it would cost a lot. According to the definition, Tao et al classified CUP into two states 10 : Type 1 refers that tissue of origin cannot be determined by pathological examination and immunohistochemistry of the metastatic cancer; Type 2 means that tissue of origin can be identified by pathological examination and immunohistochemistry of the metastatic cancer, resulting in that the T staging is defined as T0. Moreover, it was reported that type 2 of CUP exhibited better prognosis than the type 1 in the study of Tao et al 10 Metastatic adenocarcinoma of unknown primary site (MACUP) is the most common CUP 20 and signals an unfavorable prognosis.…”

“…According to the definition, Tao et al classified CUP into two states 10 : Type 1 refers that tissue of origin cannot be determined by pathological examination and immunohistochemistry of the metastatic cancer; Type 2 means that tissue of origin can be identified by pathological examination and immunohistochemistry of the metastatic cancer, resulting in that the T staging is defined as T0. Moreover, it was reported that type 2 of CUP exhibited better prognosis than the type 1 in the study of Tao et al 10 Metastatic adenocarcinoma of unknown primary site (MACUP) is the most common CUP 20 and signals an unfavorable prognosis 4 . Considering the data availability, we planned to include the MACUP patients whose potential primary sites were identified by pathological examination and immunohistochemistry, and next profiled their demographic variables and tumor characteristics.…”

“…In some CUP cases that T staging is classified as T0, the primary site could be determined by pathological examination and immunohistochemistry, although no tumor site of origin could be detected by imaging examination. Compared with other CUP, the overall survival of these T0NXM1 patients is significantly prolonged 10 …”

“…Compared with other CUP, the overall survival of these T0NXM1 patients is significantly prolonged. 10 Therefore, we aimed to analyze the relationship between clinical characteristics of MACUP and different origin tumor sites determined by pathological examination and immunohistochemistry, and to study the survivals of the origin sites, based on the Surveillance, Epidemiology, and End Results (SEER) database. In this study, we focused on the primary tumor sites of digestive system, respiratory system, and female breast.…”