Sacral chordoma : A review of literature

Abstract

Chordoma is a rare malignant tumor with predilection for the sacrum. A favorable outcome depends on early diagnosis and surgical excision with tumor free margins.

Aim

To review the incidence and prevalence of sacral chordoma and the appropriate surgical management and formulate a criteria for early diagnosis.

Materials and methods

Thirty eight articles on the subject of sacral chordoma and extrapolated data of clinical and surgical significance.

Results

The commonest presenting feature in patients with sacral chordoma was lower back pain which was worse on sitting and up to a third of these patients had associated urinary tract infections, constipation or symptoms of disc herniation. The hallmark of sacral chordoma is lower back pain with poor response to non-steroidal anti-inflammatory drugs.

Disease free eradication in chordoma is rare and not without neurological deficit. The common sacral levels involved ie. S2,3 have to be sacrificed to achieve adequate margins4. Whilst wide excision via posterior surgery shows a decrease in recurrence, the overall survival still remains low.

1. Introduction

Chordoma is a malignant, slow growing and locally aggressive tumor. It arises from remnants of the notochord and accounts for 1–4% of all primary bone tumors¹,⁶,⁷. Although reported to be rare, chordoma is the most common primary malignant tumor found in the sacrum³⁹.

The insidious onset and trivial symptoms caused by sacral chordoma may account for the late presentation³¹. These tumors are unfortunately diagnosed at a stage where prognosis is poor. The majority of patients are diagnosed in Eneking stage IB which, due to the close proximity to neurovascular structures in the sacrum and pelvis, present a challenge to the treating surgeon ⁴,⁵,¹². Chordomas are slow growing tumors and are not amenable to chemotherapy or radiation³². The first line of treatment is usually wide surgical excision.

However, excisional removal of the tumor is not without its complications, due to resection of the proximal sacral nerve roots. Many patients suffer urinary incontinence, sexual dysfunction and weakness of the lower limbs.

The tumor grows within the sacral foramina and obstructs the neural canal proximally. Posteriorly the tumor tends to invade the muscles around the hip and pelvis as well as the sacroiliac joints. Anterior invasion is uncommon due to the tough presacral fascia and thus the rectum is usually spared¹⁰,¹⁴,²⁴. Metastases of sacral chordoma occur late in the disease or even many years after surgical resection. The literature reports secondaries found in lung, bone, liver, lymph nodes, soft tissue and skin.

Recurrence many years after surgery can be explained by satellite lesions seeding via the tumors psuedocapsule which makes it difficult to achieve disease free surgical margins.

We undertook a review of the published literature on sacral chordoma from 1995 to 2014. Level 2,3,4 and 5 studies were included in the study and criteria for exclusion were chordoma present in regions other than the sacrum as well as unpublished literature.

The aim of this article is to highlight the clinical significance of this tumor and its prognosis.

2. Embryology

The spine develops from mesodermal structure known as somites. The development of somites proceeds from a cranial to caudal direction which occurs on either side of the notochord and neural tube. Somites are made up of 3 layers ie. Sclerotome(vertebral bodies and annulus fibrosis), myotome and dermatome ⁴⁴.

The neural crest progresses to form the peripheral nerves, ganglia and sympathetic trunk, as well as the pia mater.

The neural tube forms by a process called neurulation. The ectodermal cells elongate to form neural plate cells. The edges of these cells thicken and migrate to the midline. Their fusion leads to formation of a hollow neural tube. This process begins on the 3rd week of fetal life and is complete by the 4th week ³⁷.

The neural tube becomes the spinal cord, and the notochord forms the anterior part of the vertebral body as well as the nucleus pulposus (Fig. 1). It is not uncommon to find remnants of the notochord in the nucleus pulposus of intervertebral discs removed during surgery ³⁸.

Fig. 1.

Embryonic development of the neural tube.

2.1. Prevalence

Sacral chordoma is the most common primary malignant tumor of the sacrum. It accounts for 1–4% of all malignant bone tumors¹,⁶,⁷.

It is predominantly seen in the caucasian population with males being more affected than females. The male to female ratio ranges from 1.4 : 1 to 2.4 : 1 ²,³,⁸.

It is typically seen in the 5th and 6th decade with a mean age of 55 years⁹. Less than 25% of patients present in the 3rd and 4th decades, majority of these have chordoma of the mobile spine and cranium³.

Unfortunately, almost all patients have extra-compartmental invasion at the time of diagnosis ⁴,⁵,¹². Symptoms are related to compression and/or destruction of the tumors neighboring structures. Communication between multiple disciplines is essential in decision making and has been shown to minimize neurological symptoms and improve patient outcome ³¹.

2.2. Presentation

A frequent referral presenting to the orthopaedic surgeon is lower back pain and quite commonly these patients are in the 5th and 6th decade. The vague symptoms produced by sacral chordoma thus poses a challenge for early diagnosis.

All patients with sacral chordoma presented with lower back pain which was typically worse when sitting and pathological in nature¹⁰,¹¹.

Pain and radiculopathy due to compression of the sciatic nerve or iliolumbar trunk was reported in up to one third of these patients¹³. A few cases with tumor presenting in the S1- S2 region had weakness or total loss of L5-S1 function unilaterally¹⁷.

Up to one third of patients presented with symptoms urinary tract infections and 10% had constipation or cauda equina symptoms (Table 1)¹,¹⁵,¹⁶,¹⁹.

Table 1.

Presentation of sacral chordoma.

Many of these patients had been treated for years for the above symptoms with NSAIDs, antibiotics, laxatives as well as steroid injections by general practitioners before the pathology necessitated further investigations¹⁶,¹⁹.

2.3. Investigations

On plain film sacral chordoma appears as a large lytic lesion which crosses the midline > 50% of cases (Fig. 3)¹⁸,¹⁹,²⁰. Lesions may occur anywhere from the first to fifth sacral vertebrae with predilection to the 2nd and 3rd sacral bodies (Fig. 2)¹,⁶,⁸.

Fig. 3.

Pelvis x-ray showing tumor mass extending across midline and involving (R) sacroiliac joint.

Fig. 2.

Chordoma involving almost the entire body of the sacrum with minimal presacral swelling due to the tough anterior fascia. (KGV Hospital 2013).

The destruction of bone extends to the sacro-iliac joints and progresses to the ilium as well as posteriorly which may cause skin changes in the lower back. Destruction of the anterior ligamentous structures as well as the L5-S1 junction leads to listhesis and pelvic instability³⁹.

A full skeletal survey must be performed to include the hips, lumbar spine as well as the skull. Technecium[99] scan may assist in localizing the pathology for a more focused review.

CT scan assists in delineating the bony extent of the lesion and is of great value in patients with chordoma to plan any surgical intervention (Fig. 4)¹⁴,¹⁹.

Fig. 4.

CT scan delineates extent of lesion and shows sacroiliac joint involvement. MRI (T2) findings show a large hyper-intense inhomogeneous mass with a pseudocapsule (Fig.5). The mass is usually lobulated or may be multilobulated ¹²,¹⁴,19, 20, 21, 22. MRI should include the entire pelvis as well as the abdomen. Santos-Rancano et.al highlighted.

the significance of the abdominal MRI and has reported metastasis in the anterior abdominal wall²³.

At surgery chordoma is commonly found attached to the piriformis and gluteal muscles which is of significance in determining the surgical approach (Fig. 5, Fig. 6).

Fig. 5.

T2 weighted saggital MRI show large lobulated chordoma invading soft tissues. Anterior extension of the tumor is seen in less than 25% and is probably due to the tough sacral fascia present on the anterior part of the sacrum10,14,24.

Fig. 6.

45–60% of sacral chordomas occur at S2-3, S1 being the least likely location for tumor.

Several authors have correlated the volume of the tumor as a predictor of the outcome¹,¹⁰,²⁵,²⁶. They have found that at the time of diagnosis sacral chordomas larger than 10 cm or a volumetric dimension of > 200cm3 invariably carried an unfavorable prognosis.

Histologically the classic chordoma mass consists of chords of tumor cells and lobules with a mucoid matrix and extensive fibrous tissue inbetween (Fig. 7).

Fig. 7.

showing physaliferous arrangement of tumor cells Image courtesy of http://www.wikimedia.org.

Physaliferous cells are pathognomic of chordoma and are characterized by their large size with a vesicular nucleus and vacuolated cytoplasm. Mitotic figures as well as bone and cartilage may also be seen.

Toru and Majunder have attributed poor prognosis to histological patterns which contain areas of high grade sarcoma and have been termed dedifferentiated chordoma¹¹,²⁷.

Sakwe and Cuenca et al. reported a cartilaginous counterpart and is termed chondroid chordoma. These tumors show chondroid differentiation and carry the most favorable prognosis. However, it is often found in the spheno-occiptial region and rarely seen in chordomas involving the sacrum²⁸,²⁹.

2.4. Differential diagnosis

Several conditions may mimic sacral chordoma and should be considered in the differential diagnosis. Chondrosarcoma closely mimics sacral chordoma both radiologically and histologically and should be high on the list of differentials. Immuno-histochemical studies may be required to differentiate these tumors histologically. Chordoma shows positive for epithelial membrane antigen (EMA), pan-cytokeratin (panCK)⁴⁰.

Giant cell tumor and Plasmacytoma are also found in the sacrum. The radiographs appear as large lytic lesions with poorly defined borders. These tumors are aggressive and expansile, and may cross the sacroiliac joint posing a radiological challenge to differentiate from chordoma.

Metastatic disease is especially seen in the sacrum in the elderly with primaries from the prostate, breast, thyroid, lung and colon. A thorough history pertaining to symptoms and previous ailments may help in guiding towards investigations (Fig. 8).

Fig. 9.

Large lobulated chordoma displacing the rectum but not invading the pre-rectal fascia. Note involvement of the femoral heads bilaterally.

Fig. 8.

Diagram showing innervation of bowel and bladder.Image courtesy of http://www.ccptr.org.

Chronic infections caused by tuberculosis and fungus should always be considered.

3. Management

3.1. Surgical

The goal of surgery in the management of sacral chordoma is eradication while retaining as much function as possible.

Meticulous planning the level of resection is important and requires careful assessment as tumor may extend via the sacrospinal canal into adjacent segments¹⁷,¹⁸,¹⁹ It is therefore not sufficient to determine the level of sacrectomy by assessing bony involvement alone. MRI is essential in the preoperative assessment and staging of the tumor.

Mavrogenis used target artery embolization to reduce pain as well as intraoperative blood loss and suggested that this may be the only option in patients not amenable to more invasive surgical intervention⁴¹.When possible at least one nerve root at each level of sacral

resection should be preserved. Care should be taken not to penetrate the capsule around the tumor at the time of surgery as this has been correlated with a high incidence of recurrence⁴,²¹.Sacral amputations below the level of S1 show great variance in neurological outcome. Motor deficit is rare but saddle anaesthesia and loss of bowel and bladder sphincter control is commonly seen⁵.

In resections involving the S1 nerve root, motor deficits and sexual dysfunction is almost always seen. Generally, patients with sacrectomy below the level of S3 have sphincter control with some perineal anaesthesia. In all cases, the lumbosacral trunks and Sciatic nerves should be protected where possible.

Gunterberg et al reported that one side of the sacroiliac joint may be removed before weight bearing was affected. Total sacrectomy however results in gross instability of the spino- pelvic junction and stabilizing procedures must be done before any mobilization⁴².

Ishida reported that spinopelvic reconstruction following sacral tumor resection requires three components ie. Anterior column support, posterior pelvic ring stablisation and spino- pelvic fixation. S2 alar-iliac screws has shown to have the greatest mechanical strength at

the lowest risk of visceral damage and blood loss. Fusion across the sacro-iliac joint however is rare with this construct which may lead to early osteoarthritis and require removal of the screws⁴³.

There has been much debate around the most appropriate approach for excising the tumor mass. While some authors advocate a posterior only approach³⁵, others believe that a combined anterior and posterior surgery is beneficial in reducing reccurrences³⁶.

The posterior only approach has been successfully carried out with good results at a number of institutions³⁵. The rate of recurrences has been shown to be marginally lower than that of the combined anterior approach (Table 2)³⁶. This approach however may not be possible with tumors involving bowel and other viscera³⁵.

Table 2.

Posterior only approach has provided favorable outcomes on long term follow up. Anterior surgery requires an access surgeon as abdominal contents may show gross distortion due to tumor size or adhesions (Fig. 9). It provides direct access to the prerectal fascia and allows for bowel resection if needed. In cases where a layer of fat is still present anterior to the sacrum, the rectum can be left intact and a colostomy may not be required ⁴¹.

Author	No. of patients	Site	Surgical procedure	Recurrence	Metastases	Survival	Urinary / fecal incontinence
G. Housari	13	S2-5	Posterior	30% at 2 years	45% at 5 years	27% at 10 years	90%
M. Waisman	5	S2-3	Posterior	20% at 5 years	0% at 5 years	100% at 5 years	20%
A. Asavamongkolkul	21	S1-5	Posterior	0% at 2 years	9% at 7 years	5% at 7 years	100%
M. Clarke	30	S1-4	Posterior	20% at 5 years	6% at 3 years	96% at 4 years	67%

The combined anterior and posterior approach were previously reserved for tumors more than 10 cm and always included a colostomy⁵. The achievement of a wide resection came at the expense of increased morbidity and mortality. In a study done by Ozger et al. in 2010 an average 9 units of blood were required during surgery and neurological deficit post operatively was not uncommon.

3.2. Radiation therapy

It has long been believed that sacral chordoma was not amenable to radiation. However, the work published by Park et al.³² showed excellent results with localized radiation post en- bloc resection. He reported a 5yr and 10yr survival or 93% and 91% respectively.

For patients who are not candidates for surgical intervention due to poor host factors(renal/cardiac etc), radiation therapy alone may be warranted. Chen et al.³³ reported a 5yr survival rate of 78% with high dose radiation in his study of patients who where not fit for surgery

3.3. Chemotherapy

Due to poor sensitivity, chemotherapy is not instituted in patients with sacral chordoma³¹ in most centres and thus surgical management remains the mainstay of treatment. An ongoing study by Stacchiotti et al documents the use of Imatinib 800 mg/day for the non-surgical management of chordoma. He has reported a benefit rate of 64% with a 9 month progression free period of the tumor³⁴.

4. Discussion

Early diagnosis of sacral chordoma still remains an issue. The time of onset of pain to time of diagnosis is almost always more than 18 months. With the advent of CT/MRI as well as the availability of bone scan and X-Ray, these tumors may very well be diagnosed at an earlier stage offering the patient a more favorable diagnosis.

Criteria should be devised which should include a close follow up plan.From this review the following risk factors for sacral chordoma are highlighted :

Patients in the 5th and 6th decade presenting with a history of 1 year of dull aching but progressive lower back pain require further investigations. Pain has been typically described as worse on sitting and commonly disrupts sleep.

A history as above together with symptoms of a urinary tract infecrtion, saddle anaesthesia and/or constipation warrants an earlier follow up.

A plain film radiograph and inflammatory markers will help categorise patients into high or low risk.

Unlike most bone and spinal tumors, sacral chordoma does not have its own classification. The Weinstein-Boriani classification of spinal tumors does not hold much significance in management of sacral chordoma as the sacrum and surrounding structures require a different surgical approach.

The enneking classification serves as a more useful tool in staging and preoperative planning. Prognosis can be more accurately determined after biopsy and CT/MRI results.

With regards to management, a multidisciplinary approach must be adopted as resources permit. Although the frequency of recurrences is high, radical resection provides a longer disease free interval which may be further prolonged with radiation after surgery.

The posterior only approach has provided favourable results³⁵ when compared to the anterior approach. The combined approach has shown a greater margin of resection but at the expense of patient mortality with no increase in long term survival⁵.

All patients should be counselled on the high likelihood of loss of bowel and bladder function post operatively. Males in particular must be made aware of the loss of sexual function.

The posterior only approach has yielded favorable results and carries a lower risk of haemorrhage but may not always be possible where visceral adhesions are present.

Funding

No funding was received for the above study.