1 Introduction

The incidence and histological type of spinal cancer is diverse. It is country specific and has distinctive demographics. It's epidemiological trends are complex and multifactorial. However, as a nation, we are poor to document these unique characteristics. According to the recent census carried out in April 2022, the population in the Republic of Ireland has reached 5.1 million people. This is highest population count since the census of 1851. While this demographic is considered small in contrast to others, it does not excuse the fact that there are little population-based studies that define the epidemiology of all spinal cancers here in the Republic.

Although, the management of primary and metastatic spinal disease has changed considerably over the last number of years. Surgical technique and patient survival have improved and increased exponentially. It is the recommendation of international guidelines that we promote spinal surgical input for malignant spinal cord compression. However, treatment strategies for spinal tumours are rarely applicable to all and must be devised on an individual basis. For this, we need valuable demographic information.

In 2020, the European Cancer Information System (ECIS) announced that Ireland had the highest cancer rates of all the 27 Countries of the European Union. According to the Irish Cancer Society, 1 in 4 deaths in Ireland is caused by cancer each year. That is over 9000 people, accounting for approximately 30% of deaths nationally per year. Improved medical and oncological treatments are leading to increased survival times. In this current climate, an understanding of primary spinal and metastatic disease demographics is essential to guide healthcare strategy. Independent of the histological typing, it is our role as physicians to explore the epidemiology of spinal cancers so that several projections can be made. Resource allocation, cost analyses, and the requirement of rehabilitation facilities all need to be considered.

Examination of spinal oncological trends here in Ireland may also allow for the development and implementation of primary or secondary prevention strategies. For example, with the use of diet and smoking cessation in primary disease or the use of adjuvant or neoadjuvant therapy in the case of secondary disease. Prolonged evaluation of the demographics of spinal cancers will have the ability to interpret the success and failures of such prevention strategies over time.

A tertiary referral centre for spinal injuries, the National Spinal Injuries Unit (NSIU) at the Mater Misericordiae University Hospital (MMUH) in Dublin is a focal point for the management of spinal oncological cases requiring intervention here in the Republic. It is an eight-bedded specialist unit that now serves a population of 5.1 million and a geographical area of approximately 70,273 km².

It is the aim of this study to examine the epidemiology and demographics of patients referred and operated on for spinal primary and metastatic cancers over a decennary in the NISU. The objective of this paper is to provide an account of the acute oncological admissions to the NISU in both 2010 and 2020 in the hope that upward trends will be noted. It is the author's hope, that even in the presence of the COVID pandemic, that a significant increase in patients presenting with spinal primary and metastatic disease requiring fixation will be illustrated. Only by exemplifying this trend, will it highlight the need to give spinal cancer the attention it deserves in the Republic of Ireland.

2 Inclusion & exclusion criteria

All patients referred to the national spinal injuries unit with spinal primary or metastatic cancer were included in this study. All patients without the required data were excluded from the analysis of this study. The inclusion and exclusion criteria are shown in Table 2.

3 Methods

After establishing available literature, all patients who underwent spinal surgery for primary or metastatic spinal cancer in the Mater Misericordiae University Hospital (MMUH) in 2010 and 2020 were included in this retrospective cohort study. The primary investigator (PI) obtained a list of medical record numbers (MRNs) for all patients who underwent spinal surgery using the theatre log books, cross referenced by the National Spinal Unit's, “Spinal Portal”, and “Patient Centre”, databases.

Available data was combined to produce a dataset which was used to investigate epidemiological trends in spinal cancers over a decade. Data pertaining to patient demographics (age, gender), type of referral i.e. elective or emergent, referring hospital, spinal region affected, surgical procedure undertaken, tumour histological type, length of hospitalisation, and post-operative complications were noted. Ethical approval was obtained from the research ethics committee at the MMUH.

4 Results

A total of 90 patients we included in this retrospective cohort study. 37 patients in 2010, had increased to 53 by 2020. This is a 43% increase, despite the prevalence of COVID in 2020. Male to female ratios were similar for both years. In 2010, male to female sex ratio (M:F) 1.3:1.0, with an average age of 61.03 ± 14.20 (range 28–85). For 2020 the (M: F) was 1.25:1.0, with an increase in the average age 65.23 ± 12.16 (range 40–83).

For presentation, 2010 saw more elective referrals, 16.2% (n = 6), compared to in 2020, where only 5 patients were referred electively (9.4%). Emergency referrals still encompassed most of the referrals 86.5% (n = 32) and 83% (n = 44) respectively. Back in 2010, the MMUH was the main hospital noting the presentation of spinal oncology patients. Interestingly by 2020, the NSIU received more referrals from outside establishments, than in house referrals. The most common of these being University Hospital Waterford and St. James Hospital, Dublin. See Table 5 a&b.

In line with most previously published literature, metastatic disease to the spine was still the most prominent reason for referral. In 2020, metastatic disease burden made up 86.5% of all referrals to the NISU. Interestingly, this decreased to 83% in 2020. Primary spinal cancers in 2010 made up 13.5% of referrals (n = 5), this saw an increase of 3.5% by 2020 to 17% (n = 9). With regards to spinal region affected, the thoracic region was the most commonly region affected for both years, 51.4% (n = 19) and 58.5% (n = 31) respectively.

On examination, the most prevailing metastatic cancer to the spine in 2010 was breast cancer n = 7 (23%). This was followed closely by prostate cancer and multiple myeloma, both n = 4 (14%), see Fig. 1. By 2020, the most prevalent metastatic cancer had changed to lung, see Fig. 2. This was followed closely by prostate and breast, n = 8, and n = 7 respectively. For primary spinal cancers, the most common type in 2010 was Osteogenic Sarcoma and in 2020, Chordoma, both n = 2. See Figs. 3 and 4.

As expected, the most common surgical procedure performed for both years was a posterior spinal fusion, 67.6% in 2010 and 90.6% in 2020 respectively. In 2020, interestingly, the next most common choice of management was either debulking surgery or conservative/palliative management, both n = 4 (10.8%). By 2020, the second most prevalent surgical procedure was an anterior cervical discectomy and fusion (ACDF) n = 4 (7.5%) with no patients managed conservatively.

Looking at post-operative complications, anaemia was the most prevailing complication in 2010 n = 3 (8.1%). In 2020, remarkably, no patient required a blood transfusion post operatively, however the most common post-operative complication that was year was urinary incontinence, with greater than 1:10 patients being affected n = 6 (11.3%). For a full list of post-operative outcomes, see Table 6.

Naturally as more patients underwent surgical fixation, more patients’ higher levels of care post operatively. In 2010, saw more patients going to the High Dependency Unit (HDU) 29.7% than the Intensive Care Unit (ICU) 8.1%. Conversely, 2020 saw more people going to ICU than HDU, 15.1% and 5.7% respectively. 2010 saw a total of 37.8% i.e., nearly 1:4 patients requiring higher levels of care. This decreased to a total of 20.8% by 2020 1:5. Exploring the mean length of stay in ICU and HDU, the average length of stay decreased from 5.4 days in 2010, to 4 days in 2020. This significant decrease was also seen in relation to the mean length of hospital stay, plummeting from 23.6 days in 2010, to only 7.6 days in 2020. Unfortunately, the same could not be said for the 30-Day Mortality Rate, increasing from 5.4% in 2010, to 9.4% in 2020.

Finally, on investigating patient follow up, 70.3% of patients were seen back at follow up in 2010, this has increased to 75.5% by 2020. The mean follow-up in 2010 was 4.2 weeks, increasing to 5.8% by 2020.

5 Discussion

As forementioned in the introductory piece, we are a small country. A review of the literature noted one paper published on the epidemiology of spinal cancer in Ireland. This is not predictive. The paper, a recent publication in October 2020, focused on metastatic bone disease here in Ireland. McCabe et al. included patients with known metastatic cancer to bone between the years 1994–2012.¹ This is, at this point in time, a decade ago.

The demographic data for this paper was obtained from the National Cancer Registry Ireland (NCRI). It focused on all patients with metastasis to bone, not specifically spine. While spine was not the primary focus of the paper, the article did note that the spine specifically, was the main bony metastatic site (47%) and overall skeletal site (44%).^1,2 Over a 19-year period, 14,495 cases of metastatic bone disease were diagnosed in the Republic.^1,2 The median age at primary diagnosis was 72 years old, interquartile range (IQR) 62–77.^1,2 The median age fell as the years progressed from 72 to 67 years of age (CI − 5 to 0, Mann–Whitney p < 0.001).^1,2 This differs from the above research which suggested an increasing age of diagnosis as the years progressed. In this paper, males also made up most of the cases established at 62%.^1,2 This was mimicked in the current research.

One of the more alarming features of the study by McCabe et al., was that the cases of bone metastasis more than doubled from 497 per year in 1994/1995 to 1033.5 per year in 2011/2012.^1,2 That was a 108% rise. In the 10-year period of the above study, an increase of 43% was noted in relation to disease presentation.^1,2 This is despite the COVID pandemic.

Focusing on the histological types presented in the paper by McCabe et al., the major primary types affecting individuals included lung (29.6%), prostate (25.8%), breast (14.3%), gastrointestinal (7.6%), renal (4.3%) and thyroid (0.4%).^1,2 Looking at the figures in 2010 and 2020, breast, lung, and prostate featured heavily. However, while McCabe et al. noted that lung and breast cancer proportionally increased, they noted a proportional decrease in prostate cancer.^1,2 This was not the case in the current study.

The take home point from McCabe et al. noted increases in incidence of bone metastasis across both genders and all age groups as seen in the above paper. With spine as a major site of bone metastasis,¹ maintained that given the rapid growth of cancers in our population, that patients may be left exposed to potentially serious adverse events. Therefore, they advocated for prudent resource planning. To do this, they expressed the need for records to be kept. They felt that these records should focus on the directed prophylactic and therapeutic treatments of metastases here in the Republic to allow for accurate evaluation and guidance of future care¹. This is still not being fulfilled.

While McCabe et al. provide an excellent portrayal of how cancer is proliferating in this country, it does have its limitations. As touched on, these numbers are already ten years old. The article does not delve into the demographics of where, specifically in the Republic, these cases are being referred from. This study does not remark upon treatment modalities, for example, types of surgical fixation. As a result, it does not refer to post operative outcomes or complications and does not reveal the follow up, if any, of this specific patient cohort.¹

Another abstract, also by,³ presented at the Irish Spine Society's Annual Conference 2018, investigated, and included patients with biopsy proven or MDT consensus malignancy of the spine. These patients were treated surgically at University Hospital Galway (UHG) from 2010 to 2018.³ 196 patients were included over the 8-year period.³ The abstract observed an increase in the average number of patients undergoing surgery for malignant disease i.e., 20 to 29 patients, with the most common types noted to be breast, myeloma, lung, prostate and renal.³ This is in line with the current research. McCabe et al. pointed out the clinical responsibility we have to spinal cancer patients. However, this abstract was not all inclusive, given the fact that primary spinal tumours and local invasion to the spine were excluded from their patient cohort.³ Given the fact that metastatic disease provides the true burden of disease in this country, the numbers were not representative.

Two recent research abstracts submitted to the University College Dublin (UCD) School of Medicine Summer Research Awards in 2021 touched on retrospective spinal cancer trends at the NSIU Dublin. The first abstract by Flaherty et al., 2021,⁴ looked specifically at primary spinal tumours, unlike previous research. The piece included all primary spinal tumours referred to the NSIU since 1992.⁴ A total of 31 cases were noted and demographics were obtained.⁴ Flaherty et al., 2021 noted a post operative complication rate of approximately 75%, a mortality rate of near 20%, and a mortality rate approaching nearly 50%.⁴ While primary spinal cancers exist, they are exceedingly rare. They do not place the same strain on the Irish Healthcare system as their metastatic counterparts. That is why it is essential on reviewing national numbers, that they are all encompassing.

Another abstract submitted to the same conference looked admissions to the NSIU from 2016 to 2020 i.e., over a four-year period (Wilson et al., 2021).⁵ The aim was to analyse admission trends to the unit to allow for resource planning.⁵ The patient cohort was restricted to those over the age of 65 with cervical injuries. 52 patients met this inclusion criteria, 7 of whom had spinal tumours.⁵ The summation was that those with worse neurology, had longer hospital stays, and higher rates of mortality.⁵ While the author agrees that it is pertinent that we take such information into account when deliberating if patients should undergo operative management, it is not representative of all patients with spinal cancers.

At the Irish Spine Society's Annual Conference in 2019, a preceding abstract concentrating on Irish trends in spinal cancers was presented by.⁶ This presentation aimed to identify the most common tumour type operated on in the NSIU over a 12-year period (2006–2018).⁶ Breast and prostate were the most common malignancy noted, which differed from¹ results from 1994 to 2012.⁶ This emphasises the ever changing demographics of spinal cancers and stresses the need for continuous epidemiological trends to permit healthcare planning.

2009 also saw a paper published from the NSIU, by Lenehan et al.⁷ This was a prospective demographic study which looked at the epidemiological data of all acute admissions to the NSIU from 1999 to 2003 i.e., a 5-year period.⁷ Over this timeframe, the study saw 686 admissions, of which neoplasia made up 7.5% (n = 71).⁷ While the primary focus of this paper was spinal trauma, and how it could be used to formulate the future development of the unit, it did demonstrate how demographic data could be used to distinguish key areas to allow for healthcare projections and guide healthcare strategy.

It is not just in the Republic where the recognition for a need for spinal disease service provision is being highlighted. A letter to the Editor published in the Ulster Medical Journal back in 2012 observed the “ever increasing demand for metastatic spinal surgery” (⁸ pg. 156–157). They observed great increases in numbers undergoing surgery for malignant spinal cord compression (MSCC) over a ten-year period (2000–2010).⁸ 18 patients in 2000 underwent decompressive surgery in comparison to 78 patients, 10 years later.⁸ Even over a decade ago, increasing numbers could be seen, stressing the importance of “appropriate resource planning” (⁸ pg. 156).

As discussed, various abstracts and papers have documented demographical information on spinal cancer over different periods. The Irish Spine Society's Annual Conference in 2018, saw a neurosurgical focused abstract from Cork presented, emphasising the epidemiology of spinal tumours undergoing operative management from 2004 to 2017.⁹ During this timeframe, 139 patients underwent 162 procedures.⁹ Various tumour histological types were noted, the most common being glial tumours 23% (n = 37) and schwannoma 20% (n = 33) respectively.⁹ A combination of complete surgical resection n = 86 (53%) and debulking surgery were discussed n = 67 (41%).⁹ They also reviewed post operative complications which mostly included motor weakness, CSF leak, infection, and urinary retention. This abstract was the first noted piece of research outside of Dublin or Galway, which had a focus on spinal tumours, which also included metastatic disease.⁹ What stood out, was this abstract's mention of post operative complications. This had not been focused on by other papers.

Post operative complications allow for the critical analysis of the efficacy surgical procedures. They provide information on whether surgery can be considered a success or a failure and whether certain procedures are more futile than fruitful. This is essential information as we review our practise over time. While the demographics may not yet exist in the Republic in relation to the effect that spinal surgery has on oncological patient's life expectancy, what is important, is quality of life. With advancements in medical oncology, patients with both primary and metastatic spinal disease are living longer. In 2008, the National Institute for Health and Care Excellence (NICE) published their guidelines on the diagnosis and management of metastatic spinal cord compression in adults with cancer.¹⁰ These guidelines promoted spinal surgical input.¹⁰

On review of the literature, a couple of papers have looked at the evolution of spinal surgery here in Ireland. A paper out of Galway in 2016 looked at spinal surgery trends in UHG over a 7-year period (2005–2013).¹¹ This period seen a rise in the total number of spinal operations performed, with an increasing trend towards multilevel spinal surgery.¹¹ This era also saw an increase in all aetiologies of spinal pathology, with the exclusion of infection. Based on the results of this paper, the authors support the need to plan for future service provision, specifically in relation to teaching and training within the area of spinal surgery.

Also from the Irish Medical Journal in 2020, was a descriptive article published by Leddy et al.¹² The aim was to discuss the, “individual and multimodal approach”, to the management of spinal tumours (¹² pg. 128). This paper illustrated the different types of primary spinal malignancy and haematological malignancies that can present in the vertebrae along with a discussion of the various treatment modalities that exist.¹² These including Stereotactic Radiosurgery (SRS) and Intensity-Modulated Radiotherapy (IMRT), along with surgical treatment in the form of Separation Surgery, En Bloc resection, Decompressive and Stabilisation surgery, and Cement Augmentation, Kyphoplasty, and Vertebroplasty.¹² While this paper gave a good overview of the existing treatments, it did remark that no one treatment fits all. The decision to operate on this patient cohort is dependent on numerous factors including patient pain, vertebral stability, and existing or impending cord compression.^12,13 As a result, it is crucial that data exists in the country looking at the surgical intervention applied and the patient outcome from same¹³. Only in this way can we make informed decisions on what the best individual treatment strategy to apply.

A poster that gathered some of this abovementioned data was on show at the Royal Academy of Medicine in Ireland (RAMI) Intern Study day way back in 2012.¹⁴ This poster, presented an analysis from UHG on their clinical practise in the management of MSCC.¹⁴ They identified 34 patients over a 3-year period (2006–2009) who had MRI evidence of MSCC.¹⁴ Radiotherapy alone was the most common therapy used for patients with MSCC.¹⁴ A surgical opinion and a multidisciplinary approach were only taken in the minority of cases.¹⁴ This is not congruous with NICE guidelines. The poster did mention that this may be representative of some centres in Ireland having no spinal surgeons as staff.¹⁴

Not all centres can have spinal surgery as an in-house specialty. It takes specialist equipment, surgical education and expertise. This is why we have tertiary referral centres such as the NSIU. An interesting paper which was reviewed, considered the impact of COVID on the referral patterns to the NSIU.¹⁵ This paper noted a significant reduction in the referral numbers for malignancy, down 33% in 2020.¹⁵ This paper not only demonstrated how important the referral process is, so that patients receive the best possible care, but the paper also validates the relevance of secondary and tertiary prevention strategies. Noting the affect that COVID had on patient malignancy demographics, supports the need to make patients aware of indicators of disease. This is essential if patients are to present early.

6 Conclusion

Spinal primary and metastatic disease can result in debilitating injury requiring hospitalisation, surgical treatment, and prolonged rehabilitation. While the proportions and causative types of spinal cancers have changed over time, one thing is clear. That is, that the results show a substantial rise in the incidence and prevalence of both primary and metastatic spinal disease here in Ireland. This is leading to a continued growth in the workload for the Republic's limited spine services.

More operations mean more potential complications. However, as we progress as a nation, one can see clear improvements in operative technique, seeing less patients proceed to higher levels of post-operative care, and more patients getting home earlier.

The study is not without its limitations. This is a largely observational, single centre study which set out to capture those patients requiring in-patient hospitalisation and surgical treatment for spinal cancers. The data presented is influenced by the Covid Pandemic, such that overall referrals to the NSIU during the time frame was substantially reduced. This should be taken into account when comparing the data with future studies.

This paper outlines the epidemiology of spinal cancers admitted to a national centre. It is the author's opinion that the data included can be used to plan future unit development. Not only does it highlight the economic cost of spinal oncological care, but it also identifies key areas where preventative campaigns can be targeted.

Source of financial support

None.

Ethical statement

In accordance with established guidelines and regulations governing research practices, the nature and scope of this study did not involve any activities or interventions that warranted ethical approval. The research adhered strictly to principles of integrity, transparency, and respect for all participants involved.

Guardian/patient's consent

NOT APPLICABLE.

Ethical statement

NOT APPLICABLE.

Source of financial support

None.

CRediT authorship contribution statement

Amanda O'Halloran: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Resources, Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Supervision, Project administration. Christopher McKee: Validation, Resources, Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Supervision, Project administration. Gráinne Cunniffe: Validation, Resources, Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Supervision, Project administration. Seamus Morris: Validation, Resources, Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Supervision, Project administration.