Carbon Ion Radiotherapy for Rare Skull Base Tumors

What Is Carbon Ion Radiotherapy?

Carbon-ion radiation represents an innovative type of radiotherapy. A multidisciplinary approach is required to treat cancer, which comprises radiotherapy, chemotherapy, and surgery. The carbon-ion beam represents the highest level of particle radiation techniques.

What Are Skull Base Tumors?

Skull base tumors develop beneath the brain in the skull's base. It is a highly complex structure that traverses each nerve in the body that supplies and receives signals from the brain. This region harbors tumors due to its proximity to vital blood vessels and nerves of the brain, spinal cord, skull, and neck. These tumors can develop internally and externally in the skull.

What Characteristics Determine Carbon-ion Radiotherapy?

• Accurate Radiation Treatment of a Tumor Buried Deep: One of their basic physical characteristics is that carbon-ion beams release their maximum energy near the end of the beam's range and deliver comparatively low doses on approach to the target. The "Bragg curve" refers to this feature, while the "Bragg peak" designates the location of the greatest energy deposition. The Bragg peak's position and form are adjusted to the tumor region in three dimensions as part of the technical approach of carbon-ion radiation therapy. Consequently, the dose can be suppressed in the normal tissues around the target and concentrated on it.

• Potent Ability to Destroy Cancer Cells: Compared to photon and proton beams, carbon-ion radiation therapy can destroy cancer cells. Carbon-ion radiation is far more effective than photon and proton beams in eliminating cancer cells. It is consequently more effective for malignancies resistant to traditional photon/proton radiation.

• Shorter Course of Therapy: Intensity-modulated radiation therapy (IMRT) requires around 40 fractions of radiation to treat prostate cancer, but carbon-ion radiotherapy only needs 12 fractions.

For stage I lung cancer, stereotactic radiotherapy (SRT) only calls for one carbon-ion beam irradiation, although SRT often takes four or six portions. A shorter time frame is used to compare carbon-ion with traditional radiation.

What Are the Indications and Manifestations of Skull Base Tumors?

The majority of skull base tumors are asymptomatic. Symptoms, when they occur, can exhibit significant variation. Typically, the presence of the tumor is the cause.

• Exerting force on the brain.
• Impacting the secretion of hormones in the pituitary gland.
• Constricting the optic nerves.

What Is the Diagnostic Process for Skull Base Tumors?

• Physical Examination: To detect a skull base tumor, a physician performs a physical examination to identify symptoms such as epistaxis or nasal obstruction. A healthcare professional may do visual and auditory assessments and a neurological examination to evaluate the reflexes, equilibrium, and muscular mobility. In addition, our medical professionals may prescribe one or many supplementary procedures to diagnose skull base tumors accurately.

• Magnetic Resonance Imaging: Magnetic Resonance Imaging (MRI) scans are typically employed to diagnose skull base tumors. MRI employs a magnetic field and radio waves to generate three-dimensional images of anatomical structures within the body. This imaging technique is particularly valuable for visualizing the soft tissues of the cranial base. Before the scan, experts may administer a contrast dye intravenously to augment the MRI images.

• Computed Tomography (CT) Scans: Tumors in the skull base develop near the bones, resulting in bone deterioration, bone remodeling (replacing old bone tissue with new bone tissue), or excessive bone production. Chordomas and chondrosarcomas cause significant damage to the bones of the skull base. A CT scan is a highly accurate technique for observing bone alterations, and it is employed with MRI scans to diagnose and analyze tumors and adjacent tissues. CT and MRI scans are utilized in conjunction to facilitate surgical planning.

• PET Scans: A positron emission tomography (PET) scan can assist a physician in ascertaining the spite of a skull base tumor and its specific classification. During this examination, a physician administers radioactive glucose, sometimes known as sugar, into a vein. This chemical accumulates in malignant tissue and is visible on PET scan images. In cases when there is a possibility of a cancerous tumor spreading, the doctor may employ a PET scan to get comprehensive images of the complete body.

• Angiogram: If imaging tests show that the tumor is infiltrating vital blood vessels or receiving blood from nearby blood vessels, the doctor may request an angiography. This X-ray examination produces images of the blood vessels.
  • Before conducting the X-ray, medical experts administer a contrast dye into the arteries that provide blood to the base of the skull. This is done to enhance the clarity and precision of the images of the tumor and the adjacent blood vessels.
  • During an angiography, physicians may opt to do a tumor embolization procedure. This procedure entails the administration of chemicals into the blood arteries that nourish the tumor to obstruct its flow. This approach additionally minimizes hemorrhaging during surgical procedures.
• Nasal Endoscopy and Laryngoscopy: Physicians do these examinations to determine the presence of a visible mass in the nasal cavity or nasopharynx, which is the region located behind the nose in the upper portion of the neck.
  • Laryngoscopy is a medical procedure that entails inserting an endoscope, which is a slender tube equipped with a video camera, into the neck and windpipe to examine the voice cords and assess their mobility.
  • Medical professionals employ nasal endoscopy to assess the nasal cavity and sinuses of individuals experiencing nosebleeds or nasal obstruction. During this operation, experts utilize an endoscope to examine the nasal cavity for the presence of malignancies. Nasal endoscopy can be conducted at the physician's office by applying a local anesthetic.

• Biopsy: Medical professionals occasionally conduct a biopsy, a procedure in which they extract a small portion of tissue for microscopic inspection to aid in diagnosing skull base cancers. If an imaging test fails to yield sufficient information regarding a tumor, a physician may opt to extract a tissue sample by a nasal endoscopy.
  • In cases where endoscopy is unable to access a tumor, doctors may choose a stereotactic biopsy, which involves surgically extracting a minuscule portion of the tumor using a small, needle-like probe. A computerized navigation system utilizing three-dimensional CT or MRI pictures of the skull base assists clinicians in precisely identifying the tumor's location.
  • If imaging studies indicate the specific type of tumor, a biopsy may be deemed unnecessary. Alternatively, the doctor analyzes the tissue of the skull base tumor following a surgical procedure to extract a portion or the entirety of it.
  • A biopsy may be considered unnecessary if a tumor is asymptomatic and not exhibiting rapid growth during observation.

How Is the Treatment Being Applied for Rare Skull Base Tumors?

Skull-based tumors are infrequent and pose challenges for complete surgical removal due to their deep placement within the head and proximity to structures such as the brain, nerves, and blood arteries. Thus, the potential solution lies in carbon ion radiation. Carbon ion radiotherapy is recommended in cases where complete surgical removal is challenging, or the patient opts against surgery. For the carbon ion RT to be given correctly, the fixation devices for each patient must first be created.

• After that, a computed tomography (CT) scan is used to plan the patient's care while still wearing restraint devices.
• A lot of the time, fusion studies like CT, MRI, and positron emission tomography are used to find the target volume; the CT image data is sent to the treatment planning system to determine the target volume is defined and the irradiation parameters (the number and direction of radiation portals) are estimated.
• The beam-scattering method (wide beam) created at NIRS or the beam-scanning system is used to plan carbon ion RT treatments.
• The NIRS method uses high-LET neutron beams to predict clinically relevant RBE values.
• The GSI method for choosing the RBE is based on the local effects model.
• This model figures out biological efficiency by taking two sets of data as inputs: one describes the physical properties of radiation fields, and the other describes how cells or tissues react biologically. The parameters for both sets are set using a modified linear-quadratic approach.

Conclusion

High-dose carbon ion radiation therapy has been used to treat radio-resistant, unrespectable tumors in the head and neck, with great success in treating ACCs, MMMs, and sarcomas. Although these cancers are not very common, not many people have been treated with carbon ion RT, as several studies have looked into carbon ion RT for head and neck cancers. More clinical data is needed to provide a complete picture of carbon ion RT works for head and neck cancers that do not respond to radiotherapy. As a result, carbon ion RT looks like a hopeful way to treat head and neck cancers that cannot be removed surgically or are resistant to radiation.