Chondrosarcoma

Chondrosarcoma is a type of bone sarcoma, a primary cancer originating from transformed cells that produce cartilage. It comprises about 30% of bone sarcomas and is notably resistant to chemotherapy and radiotherapy. Unlike other primary bone sarcomas primarily affecting children and adolescents, chondrosarcoma can present at any age and more commonly affects the axial skeleton than the appendicular skeleton.

Types

Chondrosarcoma can be categorised into several types based on histological and clinical features. The conventional subtype includes primary central (about 75% of cases), secondary peripheral (about 10%), and periosteal or juxtacortical (less than 1%). Rare subtypes include dedifferentiated (about 10%), mesenchymal (about 2%), and clear-cell (about 2%).

Symptoms and Signs

Patients with chondrosarcoma commonly present with symptoms such as back or thigh pain, sciatica, bladder symptoms, and unilateral oedema. Often, these symptoms are nonspecific, which can delay diagnosis.

Causes

The exact cause of chondrosarcoma is unknown. However, there may be a pre-existing history of enchondroma or osteochondroma. A small minority of cases are associated with genetic conditions like Maffucci syndrome and Ollier disease. Faulty isocitrate dehydrogenase 1 and 2 enzymes, which are linked to gliomas and leukemias, have also been associated with chondrosarcoma.

Diagnosis

Diagnosing chondrosarcoma involves imaging studies such as radiographs (x-rays), CT scans, and MRI. However, a definitive diagnosis requires identifying malignant cancer cells producing cartilage in a biopsy specimen examined by a pathologist. In certain cases, especially with highly anaplastic tumours, immunohistochemistry (IHC) may be necessary.

There are no blood tests available for diagnosing chondrosarcoma. Typically, the disease is discovered incidentally during investigations for other conditions, as patients often appear in good health until a noticeable lump or pain manifests. In some instances, the first indication might be a pathological fracture at the tumour site.

Treatment

Surgery is the mainstay of treatment for chondrosarcoma. Treatment varies depending on the tumour's location and aggressiveness and is usually carried out at specialist sarcoma centres. Orthopaedic oncologists or musculoskeletal tumour specialists typically handle these cases unless the tumour is in the skull, spine, or chest cavity, where a neurosurgeon or thoracic surgeon may be involved.

Limb-sparing procedures are often possible, but amputation might be necessary in some cases. Types of amputation include external hemipelvectomy (removal of half the pelvis with leg amputation) and internal hemipelvectomy (removal of half the pelvis leaving the leg intact). Hip disarticulation, or amputation at the hip, is also a potential procedure.

Chemotherapy and traditional radiotherapy are generally ineffective against chondrosarcoma, although proton therapy shows promise with over 80% local tumour control. Complete surgical ablation remains the most effective treatment, though proton therapy can aid in tumours located in difficult-to-reach areas, enhancing surgical outcomes.

Recent research suggests that inducing apoptosis in high-grade chondrosarcoma, either directly or by enhancing responses to chemotherapy and radiation, could be an effective therapeutic strategy.

Prognosis

The prognosis for chondrosarcoma depends on the cancer's stage at diagnosis and treatment efficacy. For low-grade tumours, the five-year survival rate is about 90%. However, for high-grade aggressive tumours, the one-year survival rate drops to around 10%. Regular follow-up scans are very important to monitor for recurrence or metastasis, commonly occurring in the lungs.

---

Self-assessment MCQs (single best answer)

What percentage of bone sarcomas does chondrosarcoma comprise?

Which part of the skeleton is more commonly affected by chondrosarcoma?

Which subtype of chondrosarcoma is the most common?

What is a common symptom of chondrosarcoma?

Which genetic conditions are associated with a higher risk of chondrosarcoma?

What is the primary method for diagnosing chondrosarcoma?

Which treatment is the mainstay for chondrosarcoma?

What is the five-year survival rate for low-grade chondrosarcoma tumours?

Which type of radiotherapy shows promise in treating chondrosarcoma?

What is a possible indication of chondrosarcoma in a patient?