Sarcoma and chordoma

What are sarcomas and chordomas?

Sarcomas are rare cancers that develop in the bones and soft tissues, including muscles, fat, and connective tissues. They can occur anywhere in the body but are often found in the limbs, abdomen, and chest. Chordomas are a specific type of slow-growing bone cancer that arises in the spine and skull base, often affecting critical structures like the brainstem and nerves.

Radiotherapy  plays a critical role as a primary treatment for unresectable sarcomas (large bony sarcomas or large chordomas), small sarcoma metastases ( stereotactic body radiotherapy), as neoadjuvant or adjuvant in resectable sarcomas, or as palliative treatment in large symptomatic unresectable tumours.

Chordomas

Chordoma is a rare tumour which is thought to arise from remnants of the embryonic notochord (cartilage). Generally, it is slow-growing, although rarely, some chordomas can be more aggressive. It can grow anywhere along the spine column.

Managing base of skull chordoma typically involves a multi-disciplinary approach, combining surgery and radiation therapy. The anatomy is challenging due to close-ness to critical structures like the cranial nerves, eyes and brain.

1. 1. • • Proton Beam Therapy: Due to the location of base of skull chordomas, proton beam therapy may be preferred. Proton therapy delivers radiation more precisely, minimizing damage to surrounding healthy tissues.

Modern radiotherapy techniques, particularly with carbon or proton beam irradiation, have yielded excellent local control rates, even in the presence of large disease due to surgical challenges. There have been studies published by Japanese groups comparing carbon and proton beam. Outcomes are similar.

In this Japanese study published in 2018, both patients who had and did not have surgery were studied after treatment with carbon or proton beam therapy. At 5 years, local control was 85%, and results suggest patients who had good removal of tumour had better outcomes. In a more recent study published by doctors from the University of Florida using a more precise proton technology (pencil beam) reported that local control was 95% when patients had total removal versus 70%. There were no serious toxicities due to radiotherapy.

To coordinate efforts to manage this challenging and rare disease, large international groups have collaborated to publish guidelines for doctors. This includes the Global Chordoma Consensus and the ESTRO radiotherapy treatment guide.

Sarcoma

Radiotherapy plays a crucial role in the management of sarcomas, which are a diverse group of rare cancers that originate from the connective tissues, such as muscles, bones, and tendons.

• • Adjuvant Treatment:  After surgical removal of the primary tumor, radiation therapy may be employed to target any remaining cancer cells in the surrounding area.

• • Neoadjuvant Treatment: In some cases, radiotherapy is administered before surgery. This approach aims to shrink the tumor and facilitate a more effective surgical resection.

• • Palliative Care: For patients with advanced or metastatic sarcomas, radiotherapy can be used to alleviate symptoms and improve quality of life.

• • Definitive treatment: In patients whom sarcomas cannot be removed, e.g. large sacral chordoma, pelvic Ewing’s etc, radiotherapy, particularly particle treatment with carbon or protons, can offer a good chance of cure.

• •  High-grade sarcomas have a propensity for lung metastases. Stereotactic radiotherapy can still cure some patients with limited sites of disease.

In metastases to the lungs from other primary sarcoma sites, stereotactic body radiotherapy is highly effective and safe for eradication of these small spreads.

Here are some key points about radiotherapy for sarcomas:

1. 1. Types of Radiotherapy:
      • • External Beam Radiotherapy (EBRT): This is the most common type of radiotherapy for sarcoma. It involves directing radiation from outside the body toward the cancerous tumor. The patient typically lies on a treatment table, and a machine delivers the radiation precisely to the targeted area.
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      • • EBRT can be given with xray (photons) or proton therapy. In Singapore, proton beam therapy can be used for chordoma, chondrosarcoma, spinal and paraspinal bone and soft tissue sarcoma, and retroperitoneal sarcoma. Read more about proton beam therapy for sarcomas here.
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1. 1. Treatment Planning:
      • • Before starting radiotherapy, a detailed treatment plan is developed. This includes imaging studies, such as CT scans, to precisely locate the tumor and determine the optimal angles for radiation delivery.
      • • During simulation, if your tumour is near the diaphragm ( thoracic sarcoma, or retroperitoneal sarcoma), you may be asked to breathe slowly and regularly ( 4D CT scan) whereby your breathing cycle is imaged so that the tumour movement is tracked and delineated out for target planning.
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1. 1. Sessions and Duration:
      • • Radiotherapy is usually administered in multiple sessions, referred to as fractions. The total number of sessions and the overall duration of treatment depend on factors such as the type and stage of sarcoma.
      • • Treatments are typically given daily over several weeks, allowing healthy cells to recover between sessions.
      • • For stereotactic body radiotherapy, treatments range from 1 to 5 sessions.
      • • For conventionally fractionated EBRT ( 3D, IMRT, VMAT or proton beam), treatments range from 20# to 35# ( 4 to 7 weeks).
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1. 1. Side Effects:
      • • Radiotherapy may cause side effects, and these can vary from person to person.
      • • Acute side effects for cancer radiotherapy include fatigue, skin changes in the treated area and nausea.
      • • Most acute side effects are temporary and can be managed with supportive care.
      • • Long term side effects are dependent on area of irradiation. For thoracic radiotherapy, side effects include lung scarring, cardiac issues such as heart failure or ischemic heart disease. For extremity radiotherapy, lymphedema, muscles stiffness and skin changes are possible. For spinal or head and neck irradiation, nerve damage, mouth dryness and muscle stiffness are possible.
      • • Secondary cancers are possible but incidence is low.

1. 1. Combination with Other Treatments:
      • • Radiotherapy is often used in combination with surgery, chemotherapy, or both. The choice of treatment depends on factors such as the stage and type of cancer, as well as the overall health of the patient.

It’s important for individuals considering or undergoing radiotherapy for sarcomas to discuss the potential benefits and risks with their healthcare team, as well as to address any concerns or questions they may have about the treatment process.