Synchronous versus metachronous spinal metastasis: a comparative study of survival outcomes following neurosurgical treatment

Systemic tumor disease with singular or multiple spinal metastases (SM) has assumed an increasingly prominent role in the daily clinical practice of spine surgeons and the lives of affected patients (Coleman 2006; Brande et al. 2022). It is estimated that approximately 5–15% of all cancer patients will ultimately develop spinal metastases (Brande et al. 2022; Jenis et al. 1999; Jacobs and Perrin 2001). Among the primary culprits are breast cancer, prostate cancer, and lung cancer, with the primary tumor remaining elusive in 3–10% of cases (Greenlee et al. 2000; Ulmar et al. 2007).

In the therapeutic arsenal for this profoundly affected patient population, surgery stands as a common treatment modality (Furlan et al. 2022). After lungs and liver, skeletal system and bones bear the brunt of systemic metastases (Macedo et al. 2017; Maccauro et al. 2011). Surgical options for managing spinal metastases encompass a spectrum, from biopsy coupled with vertebroplasty or kyphoplasty (Stangenberg et al. 2017; Georgy 2010), to spinal canal decompression in isolation (Patchell et al. 2005), or in conjunction with minimally invasive percutaneous procedures (Miscusi et al. 2015) and open instrumentation with augmented screws (Ringel et al. 2017; Park et al. 2019a), at times necessitating anterior–posterior stabilization (Ulmar et al. 2006; Gezercan et al. 2016). The overarching objective of surgical intervention is the mitigation or prevention of neurological deficits, coupled with a focus on enhancing the patient’s quality of life (Fehlings et al. 2016; Depreitere et al. 2020). Additionally, surgery provides a means to attain a definitive histological diagnosis of the spinal tumor lesion and potentially improves overall survival (OS) (Patchell et al. 2005; Krober et al. 2004).

SM may arise within the context of a previously known and managed systemic cancer disease (metachronous presentation), often preceded by multimodal therapies, such as radiation, systemic chemotherapy, immunotherapy, or specifically targeted therapies (Gerszten et al. 2009; Berger 2008; Choi et al. 2015, 2019). Alternatively, newly diagnosed SM may serve as the inaugural presentation of a previously undiscovered systemically disseminated cancer (synchronous presentation) (Jacobs and Perrin 2001; Bollen et al. 2018; Patnaik et al. 2020).

Despite existing literature, it remains uncertain whether the choice to surgically resect SM in cases of synchronous versus metachronous presentation significantly influences surgical decisions and patient survival. This study seeks to clarify this issue by examining the prognostic implications of synchronous versus metachronous SM diagnoses, measured from the day of neurosurgical SM resection, in patients who underwent surgical intervention for SM.

This study analyzes the prognostic impact of metachronous vs. synchronous SM diagnosis in patients who had undergone surgical therapy for SM. We found that the time of SM diagnosis does not impact 1-year mortality and patient survival when measured from the day of SM resection.

In the group of patients with SM from lung and breast cancer, SM significantly more often occurred in the synchronous than in the metachronous situation. Compared with this, SM from prostate and other carcinoma significantly more often occurred in the course of the known underlying cancer disease (metachronous situation). Lung cancer is notably associated with the highest incidence of spinal metastases (SM) and brain metastases (BM). The occurrence of SM in lung cancer patients, as reported in the literature, ranges from 5% to a significant 56%. This variation is influenced by factors, such as the histological type of the cancer, the status of the epidermal growth factor receptor (EGFR) mutation, and the stage of the disease (Berghoff et al. 2016; Nayak et al. 2012; Goncalves et al. 2016; Wang et al. 2017; Zhang et al. 2020; Rizzoli et al. 2013). Similarly, SM is observed in 5–15% of breast and prostate cancer cases, making these two types of cancer among the most common to develop SM (Rizzoli et al. 2013; Hong et al. 2020; Kumar et al. 2020; Park et al. 2019b). The observed difference in the frequency of synchronous versus metachronous spinal metastasis (SM) diagnosis between lung and prostate cancer may be partially attributed to the diagnostic practices for these cancers. Prostate cancer may often be detected during routine medical check-ups for men, leading to earlier diagnosis. In contrast, lung cancer typically remains undetected until it reaches more advanced stages of the disease (Goldsmith 2014; Lux et al. 2019; Vinas et al. 2016).

Our findings regarding the distribution of cancer entities align with those reported in well-established studies (Krober et al. 2004; Hosono et al. 2005; Sciubba and Gokaslan 2006). Consistent with numerous publications, we observed that the thoracic spine was the most frequently affected spinal segment in both synchronous and metachronous SM groups (Bach et al. 1990; Comey et al. 1997). However, our study did not identify a specific dissemination pattern linked to the primary tumor, such as a preference for lung cancer metastases to manifest singularly or multiply in the thoracic spine, as noted in some reports (Schiff et al. 1998; Gilbert et al. 1978). Conversely, other researchers have observed a concentration of bronchial carcinoma in the thoracic spine and a predominance of prostate carcinoma in the lumbar spine (Krober et al. 2004).

In contemporary literature, the incidence of multiple spinal canal metastases in cases of spinal infiltration with SM is reported to be up to 30% (Sande et al. 1990). Our cohort demonstrates a prevalence with 45% in synchronous SM and 36% in metachronous SM involving more than three segments.

To the best of our knowledge, this study is the first to investigate the prognostic impact of synchronous versus metachronous SM. A notable aspect of our approach is the emphasis on postoperative survival in the survival analysis. This focus is crucial as it aligns with the typical juncture at which neurosurgeons encounter patients with spinal metastasis. These findings suggest that the indication for surgery should be considered regardless of whether the SM is synchronous or metachronous. This conclusion is significant for clinical decision-making in neurosurgery, suggesting that the timing of metastasis, in relation to the primary tumor, should not be a deterrent to surgical intervention.

In essence, our findings advocate for a surgical approach in managing spinal metastasis without bias toward the metastasis’ temporal classification. This has direct implications for neurosurgical management, underscoring the importance of considering surgery as a viable treatment option in both synchronous and metachronous scenarios and providing a clear directive for surgical intervention.

The present study indicates that the timing of SM diagnosis, whether synchronous or metachronous, does not substantially influence patient survival following surgical treatment. These findings imply that decisions regarding neurosurgical intervention should be considered independently of the temporal classification of SM.