Radiotherapy pt.1

Question 1

What is the crucial point of radiotherapy?

Answer 1

• The crucial point is to hit the target, by hitting the DNA you can induce transformation and increase
  the damages that will induce apoptosis (self-death mechanism) or necrosis.
• If you can induce a certain damage on DNA cells, tumor cells can detect that there are so many damages to induce their own death
• The damage to the DNA and on other structures is the key for the damage mediated by radiation therapy.

Question 2

What is chemoradiation?

Answer 2

The delivery of chemotherapy with radiotherapy

Question 3

Does radiotherapy take a local or diffuse approach?

Answer 3

Radiotherapy and ration oncology, similar to surgery, is a local discipline that applies a local or locoregional approach

Question 4

What can the modality of radiotherapy be?

Answer 4

• Sequential or concomitant
• Sequential means one after the other, and concomitant means that the chemotherapy that we are concomitantly administering through the
  radiotherapy has not any major aim in terms of systemic effectiveness, because it is a local approach.

Question 5

What is the aim of using concomitant chemotherapy with radiation?

Answer 5

• It aims to chemo-sensitize the tissues for the effect of radiotherapy
• Chemo is provided at very small doses because we want to make all the tissues to be sensitized, so that the DNA damage is magnified when the x-rays damage the DNA or any other target. With this in mind a smaller dose of radiation is thus required since the tissue is already sensitized
• In case of indirect damage instead chemotherapy can be used simultaneously to Cause more DNA breaks, increasing damage so the cell cannot repair the strands and will
  undergo apoptosis; Drugs like 5-FU (Fluorouracile) which inhibits thymidilate synthase (enzyme) will instead block
  DNA synthesis, so repair systems
  -In this way radioT and chemoT have a synergistic effect on the tumor cell

Question 6

What can oncological treatment be divided into based on approach?

Answer 6

• Locoregional: Radiotherapy and surgery
• Systemic: Oncology, Hematology

Question 7

What can oncological treatment be divided into based on treatment aim?

Answer 7

• Radical – curative, full eradication
• Neoadjuvant- To reduce/to prevent
• Palliative - you cannot change the survival or final outcome, you can manage the quality of life, reduce symptoms
• Benign diseases: To cure
• Prolonged checkup - can be local or general. In between the two previous mentioned aims, you can delay the final phase of the most advanced growth of the tumor, although you know the global survival will not be changed. It delays the more aggressive disease and complications, keeps the situation stable but doesn’t change prognosis

Question 8

What other conditions aside from cancer is radiotherapy used?

Answer 8

• We may treat also other benign conditions like restenosis (reduction of the vessel lumen) after an angioplasty, adenomas, AVM, trigeminal neuropathies, cardiac tachyarrhythmias
  not manageable with drugs or local ablation
• drug resistant arrhythmias, trigeminal neuralgia, Graves disease exophthalmos, arteriovenous malformations, some epilepsies and even psychosis
• This is due to improvements in radiotherapy technology

Question 9

What can oncological treatment be divided into based on modality?

Answer 9

• Adjuvant: post operative
• Neoadjuvant: preoperative
• RT+ chemotherapy, when you escalate you usually escalate the chemo, you’re treating the patient with RT and use the chemo to sensitize the patient to radiations
• External beam radiotherapy and brachytherapy
• Metabolic radiotherapy

Question 10

What is radiotherapy?

Answer 10

Radiotherapy is the killing of cancer cells by ionizing radiation (x-rays or ionizing particles).

Question 11

How does the damage to DNA occur in radiotherapy?

Answer 11

By ionizing radiation (X-rays or ionizing particles) Then, in the presence of oxygen, the DNA damage is magnified,
the oxygen increases the damage, so we prefer, if possible, to have a better oxygenated tissue

Question 12

What is the mechanism of action of radiotherapy? What can the damage to the DNA be divided into in radiotherapy? Which is seen more?

Answer 12

• Radation passes through a cell killing it or causing so many damages that apoptosis is induced. The effect of radiations is usually indirect.
• Direct and indirect
• Most of the damage is not direct: not always the x-rays, the quantum of energy, reach directly the DNA of the cell, since DNA occupies a very small part of the cell. BUT since water is 85% present in the body, the x-rays hit and energize the water that is inside the cell and produce some free radicals and ROS, that are very reactive species (like a modified version of water molecule).
• So, most of the damage is actually mediated by indirect action in the presence of oxygen or chemotherapy, this damage is fixed and is less likely to be repaired by the cell

Question 13

Describe external beam radiotherapy

Answer 13

• X rays come from outside, are generated and come inside the body
• It is the most indicated (more than brachytherapy) and easily handled method, it is also easier since the X-rays are generated so there is no exposure (doctor/technician not exposed to x-rays)
• The RT source is far out of the patient
• The RT beam pass through the patients
• The max dose is released at the level of the Target (tumor)

Question 14

Basic difference between brachytherapy and external beam radiotherapy

Answer 14

The basic difference between these 2 modalities is that the radioactive sources for brachytherapy can be brought in contact with the lesion to treat, for example inside the bronchus through needles that perform a sort of catheterization inside the
muscles, it can also occupy some other cavities like the esophagus for a superficial cancer or if there is a bulky disease that we want to make a palliation for the patient that cannot eat
anymore, or we can treat after a surgery for cervical cancer that the patient has been operated for the removal of the uterus, and a sort of reconstruction of the vagina can be done that has a high risk of relapse, so a so-called applicator that makes the residual vagina having a very regular shape, and inside the applicator a source can be inserted that will sterilize the possibly remaining cells of the cancer.

Question 15

Application of metabolic radiotherapy

Answer 15

A classic example is thyroid cancer, as the function of thyroid cells is to accumulate iodine so we can provide radioactive iodine to treat the cancer

Question 16

What could be considered an exception to the rule that radiotherapy is locoregional?

Answer 16

The metabolic radiotherapy could be the exception to the rule that radiotherapy is local, it is the only modality we can think of being a kind of systemic therapy, as it treats cell by cell
- But it is still somehow local since we inject the drug at a specific area to target a specific cell group
- Instead in chemotherapy we attack each cell, not only the tumor cells (tumor cells are more affected but it is
not very biologically selective as the metabolic radio).

Question 17

Repair of damage in healthy cells vs tumor cells

Answer 17

Normal cells can repair the damage from radiotherapy/chemotherapy much better than a tumor cell, as the tumor is affected by its growth by several transformations that it cannot deal anymore with the repair of
the damage.

Question 18

What is done before giving actual radiotherapy to the patient?

Answer 18

Since the tumor is not seen, we need to recall the image of where it is. This is the reason why there is a long preparation called the simulation, we simulate the treatment by pretending to treat the
patient.

Question 19

How many fields are used when giving radiotherapy

Answer 19

• We can single or multiple planes
• Usually, we don’t treat by one single field but multiple fields. The reason is that the higher the number of the fields the higher is the chance that they can distribute less the dose for each field
  inside the target.
• We want to use multiple fields, the simple approaches with single fields are not used anymore
• You want to distribute radiation on different fields since this way it is possible to concentrate the beams on the target. One single field will deliver all the dose of treatment, treating the target but we will have a peculiar dose distribution:

Question 20

What does prognosis depend on in radiotherapy?

Answer 20

Prognosis depends on the response to therapy

Question 21

What percentage of cancer patients receive radiotherapy?

Answer 21

Around 50% of cancer patients

Question 22

How can one be sure that the positioning of the patient is right during radiotherapy?

Answer 22

There are Vac-lock cushions on the RT couch (they inflate and vacuum themselves after positioning is confirmed), they resemble a bean bag which after positioning the patient helps
stabilize to stop them in position. They are also useful to reposition the patient often, since once the patient is locked you cannot reperform therapy, you have to have multiple sessions.

Question 23

How long does radiotherapy take?

Answer 23

• Usually therapy takes 3-5 up to 25-28 regular daily sessions
• In very few cases you can have 2 daily sessions, very few cases instead have a very short treatment period of 2-3 days.

Question 24

What affects beam attenuation?

Answer 24

The density of structures

Question 25

How are the diagnostic images for radiotherapy made?

Answer 25

• The diagnostic images are fused together to obtain a 3D model of tumor and organs. Technically it is
  a CT but there is not the contrast enhancement infusion.
• After obtaining the diagnostic images (high-detailed ones), they are merged with CT and PET images to obtain a 3D model of tumor and organs
• The energy for treatment is very high,
  so a regular X-ray source is used to
  obtain the reference images. This
  source rotates around the axis to detect
  the image. It is a 2D image and the
  process is called IGRT (image guided
  radiotherapy), while the system is OBI
  (on board imaging). Detailed images are obtained, they are called kV images and then they are overlapped with DRR
  (virtual image). Basically, it is the matching of the reality image with the theoretical and technical
  one.

Question 26

What does 3d radiotherapy mean?

Answer 26

Tridimensional radiotherapy means a tridimensional delineation of all the structures.

Question 27

Projection of the patient and its angle in radiotherapy

Answer 27

Frontal: Gantry 0 degrees
Lateral: Gantry 270 degrees

Question 28

What is cone-beam CT?

Answer 28

CBCT (cone-beam CT): rotate around the patient, capturing data using a cone-shaped X-ray beam.

Question 29

3d vs 2d radiothereapy

Answer 29

Before 3D radiotherapy (CBCT) there was a 2D radiotherapy (digital reconstruction radiograph, DRR). 2D is the only way of visualizing X-ray examination

Question 30

What is gating?

Answer 30

• Image guided radiotherapy (IGRT)
• a system that tracks a patient’s normal respiratory cycle with an infrared camera and chest/abdomen marker
• Gating= applies delivery conditions modifying RT delivery

Question 31

What is 4d radiotherapy

Answer 31

• 4D radiotherapy is born as an answer to the necessity of following what happens to the organs during the treatment.
• 4D gating system: fourth dimension, changes over the time.
• 4D gated CT scan: multiple levels of images for any point. The patient is put in the CT scan where detectors let us know in which position of the respiratory cycle we are.
• Real Time Position Management is the most used one.
  GateRT (VisionRT

Question 32

How is EBRT delievered?

Answer 32

EBRT delivers the treatment through linear accelerators and from outside.
. External beam radiation linear acceleration

Question 33

What does 3D conformed radiotherapy use?

Answer 33

3D Conformed Radiotherapy, it applies a simulator CT scan to define the density of the structures; very common.

Question 34

How is IMRT modulated?

Answer 34

Intensity modulated

Question 35

How is VMET modulated?

Answer 35

Volumetric modulated, advanced approach of IMRT

Question 36

Advantages of MRGRT

Answer 36

MR guided therapy has the advantages in terms of visualization of the target, and all of the other structures around the target
It enables the direct gating of the target

Question 37

What are the key features of continuous MRI imaging (Continuous MRI imaging)?

Answer 37

1st feature: Continuous visualization of the organs and target motion
2nd feature: Apply a gate that is directed to the structure (OAR tracking, organ at risk)
3rd feature: Apply small adaptions, acquiring new images recalculating the contouring.

Question 38

What happens in continuous MRI imaging?

Answer 38

• It can check the treatment positioning through MRI imaging, the soft tissue density differences can be enhanced for example.
• Expose the patient to continuous visualization through the whole treatment because it is without X-ray.