HUMAN BODY PRESENTATION

RadioTherapy

Presented by: Yara Agbaria & Amal fadel

Supervisor: Dr. Haytham issa

what is radiotherapy

dental management

uses of radiotherapy

effects on oro-facial area

techniques

indications

mechanism of action

doses& fractionations

what is radiotherapy

Radiotherapy is the use of high-energy x-rays, electron beams or protons to destroy and damage cancer cells and\or shrink tumors. - The decision to use radiation therapy depends on the type and stage of cancer -The major goal of radiotherapy is to achieve local control of the tumor while minimizing damage to the critical organs and normal cells.

- each cancer and each person is different, Patients often receive differently doses and fractionations. That is because different tumor cells in different locations in the body respond differently to the radiation. And as well your body responds differently to amounts of radiation.

how can we use radiotherapy to treat cancerous cells

radiotherapy used alone when: the tumor is small and haven't spread, or when the surgery could have a serious effect on the speech or swallowing, like the tumor is found in areas that are hard to reach.

Radiotherapy can be used to treat many types of cancer either alone or in combination with other treatments, as an adjuvant to surgery or in combination with chemotherapy (synergistic effect).

If a cancer is affecting adjacent tissues (locally advanced), then it is combined with other treatments. especially surgical treatments

after surgery (with or without chemotherapy) to destroy any remaining cancer cells and reduce the risk of cancer coming back.For most locally advanced head and neck cancer, surgery and postoperative radiotherapy are complementary, a combination of the two modalities achieving the optimal result. in combination with chemotherapy (chemoradiation), without surgery. in combination with the targeted therapy drug cetuximab to reduce symptoms & enhancing the quality of life (palliative radiotherapy).

How radiotherapy works on killing cancer cells?

Indirect DNA damage

Direct DNA damage

Direct DNA damage

Direct-type damage results from radiation of charged particles with high energy being deposited directly into the DNA, causing DNA double strand break down and damage at the same spot.

Direct damage is less common: heavier particles like protons rely on this form of damage.

• in this process we aim to catch the cell at it M phase
• M phase is a very radio-sensitive phase, because of its highly mitotic activity , so highly suspicious to disruption. and at this phase the cell is well oxygenated

Normal cells

cancer cells

it will be affected too by radiation.the normal cells may be at their M phase, and gets a DNA breakdown. but the normal cells heals better than cancer cells, so it can repaid itself

The cancer cells divides more rapidly than normal cells without maturation.cancer cells can’t repair itseld when the radiotherapy breaks its DNA, so it will eventually die (even if it has the ability to repair)

VS.

In-Direct DNA damage

Most of our current techniques causes indirect DNA damage. This is when radiation contacts water around target cells to cause reactions that produce free radicals, then additional contact with nearby oxygen produces an even more toxic superoxide. These radicals in turn will cause damage to the cell.

Fundamental mechanism of RadioTherapy

The 4 R's

REPOPULATION

REPAIR

Tumor cells can repopulate themselves when in completely damaged. Each fractionation of radiation must cause more damage than a tumor cells ability to repopulate, with the permission of repair to the normal cells

Normal cells repair their DNA damage better than cancer cells and fractionations allows repair.

REOYGENATION

RE-DISTRIBUTION

Tumor cells farther away from the blood supply such as in the center of a tumor are more hypoxic. Most RT damage is produced by indirect DNA damage through radicals & oxygen is key in producing very toxic superoxide radicals. fractionation causes oxygen rich tumor cells to die first, and previously hypoxic cells to be re-oxygenated. These cells will be more susceptible to radiation in the next fraction.

Tumor cells are at different places at any given times, each fractionation allows re-assortment of tumor cells to be in the M phase and allows radiation to produce considerable DNA damage

Radiotherapy dosage & fractionations

Radiation is not selective to tumor cells and therefore targets any cells that are in the process of replication when the therapy is applied. This thereby stresses the importance of administering the correct dose in order to ensure optimal efficiency with minimal side effects.

Gray (Gy) is the unit used to measure the total amount of radiation that the patient is exposed to.

No single fractionation schedule has proved to be optimal for all head and neck cancers. Conventional fractionation consists of daily fractions of 1.8 to 2 Gy, five treatments per week.

Hyper fractionation

Accelerated fractionation

Hypo fractionation

hyper fractionations

delivers two or more small-dose fractions on each treatment day and keeps the overall treatment time the same or slightly reduced. 1) higher biologically effective dose to be delivered to the tumors, 2) increases the tolerance of late-responding normal tissues. But, associated with more severe acute mucositis

accelerated fractionations

the overall treatment time is reduced, but the number of dose fractions, total dose, and size of dose per fraction are unchanged or somewhat reduced. The basic rationale is that reduction in overall treatment time decreases the opportunity for tumor cell regeneration during the treatment course.

hypo fractionations

shortens the overall duration of a radiotherapy treatment course by delivering fewer treatments but with a higher dose of radiation per daily treatment. it is beneficial when used as palliative treatment for inoperable cancers reduce side effect and enhance the quality of life.

DOSE FRACTIONATION:

Radiation therapy is usually divided or “fractionated” over a treatment course lasting multiple weeks. Fractionation in the context of radiotherapy is the process of dividing a dose of radiation into multiple “fractions”. This practice seeks to maximize the destruction of malignant cells while minimizing damage to healthy tissues.

Repair

Re-oxygenation

Redistribution

splitting the dose allows healthy cells an opportunity to repair this sublethal damage between fractions. Meanwhile, malignant with impaired DNA repair pathways are less able to recover from radiation damage to their DNA.

Fractionating R.T allows cells which are closer to sources of oxygen to be killed first, and the intervening time between fractions allows the relatively hypoxic cells to improve their oxygen supply. These cells are then more sensitive radiation.

Dividing the total dose of radiation into multiple fractions maximizes the probability of irradiating cells when they are in the most radiosensitive PHASE, M phase of their cell cycle.

general doses used in head & neck cancers

IN HEAD & NECK The optimal radiation dose depends on the size and location of the primary tumors and the neck lymph nodes. In general:

- primary tumors and gross lymphadenopathy require a total of 70 Gy or more, with a daily fraction of 2 Gy. - Radiation to low-risk neck nodal regions requires a total of 50 Gy or more. - For postoperative radiotherapy, higher doses of radiation (60 to 66 Gy), which generally required for microscopic disease to decrease the risk of locoregional failure resulting from interruption of the normal vasculature, scarring, and relative hypoxia in the postoperative tumor bed.

SCC of H&N- notes & doses used.

Radiation doses in the postoperative setting range from: - 70 Gy for gross disease - 60–66 Gy for high-risk regions and - 50–54 Gy to cover low-risk areas subject to microscopic spread. (adjuvant)

In the oral cavity, stages I and II are treated with primary surgery or definitive RT. stages III and IV (loco-regionally advanced) are treated with surgery followed by aRT with or without CRT.

Laryngeal squamous cell carcinoma is the second most common head and neck cancer. Early-stage laryngeal cancer can be managed by single modality RT without surgical resection. More advanced laryngeal cancers are typically managed with CRT for voice preservation.

Hypopharyngeal squamous cell carcinoma is typically diagnosed in the later stages of cancer (III-IV) due to the lack of clinical presentation until a bulk tumor volume can be palpated during swallowing

There are three main volumes to be considered in radiotherapy planning:1) position and extent of the primary tumour; this is known as the gross tumour volume (GTV). 2) the second volume surrounds the GTV and describes the extent of microscopic, un-imageable tumour spread (draining lymph nodes & metastatic lymph nodes) this is known as the clinical target volume (CTV). 3) the third volume, the planning target volume (PTV), which allows for uncertainties in planning or delivery, must be added, and the normal tissue structures in the vicinity of the target must be considered. (safety margins)

case

Proton beam therapy for locally advanced and unresectable (T4bN0M0) squamous cell carcinoma of the ethmoid sinus

- In principle, the clinical target volume (CTV) included the gross tumor volume and bilateral ethmoid sinuses. - and the initial planning target volume was determined by adding margins of 8–10 mm to the CTV. - To spare the surrounding normal tissues and to adapt the planning target volume to the tumor volume reduction, treatment plans were commonly changed twice to the total doses of 30–40 Gy equivalents (GyE) and 60 GyE. - A median total dose of 72 GyE was delivered at a fractional dose of 2 GyE. - Patient underwent two 28-day cycles of chemotherapy which was administered concurrently with Proton Beam Therapy.

Types of RadioTherapy

1) Internal radiotherapy (brachytherapy):

Internal radiotherapy delivers a high dose of radiation with fewer side effects than external radiotherapy. This is because internal radiotherapy delivers radiation from inside the body, close to the cancer, so affects fewer healthy cells. However, internal radiotherapy is only suitable for accessible smaller cancers. radioactive sources are placed in and\ or around the tumor.

2) systemic radiotherapy:

A type of radiation therapy in which a radioactive substance, such as radioactive iodine or a radioactively labeled monoclonal antibody, is swallowed or injected into the body and travels through the blood, locating and killing tumor cells.

3) External beam radiotherapy:

This is the most common form of radiotherapy. A beam, or combination of beams, of either X rays or electrons is directed at the tumour and/or surrounding tissues. the machine used is usually Linear Accelerator.

These high energy x-rays can deposit their dose to the area of the tumor to destroy the cancer cells and, with careful treatment planning, spare the surrounding normal tissues.

Intensity modulated radiation therapy (IMRT).

Three-dimensional conformal radiation therapy (3D-CRT).

Stereotactic body radiation therapy (SBRT)

Image-guided radiation therapy (IGRT)

Proton beam therapy.

Proton beam therapy

It uses high-powered energy particles known as protons instead of X-rays to directly deliver radiation to the tumours. Proton beam therapy delivers less radiation outside of the tumour by directing a beam of proton particles that stops at the tumour, so the chances of damage to nearby healthy tissues are low. SO ADVANTAGES ARE:

1) Minimizes damage to vital organs and lowers the risk of side effects during and after treatment.

2) Reduces the risk of secondary cancers, so its highly indicated for pediatric cancers due to the high risk of children to develop secondary cancers from their initial treatment later in life

3) we can deliver higher curative doses of radiation, due to the lower side effects

forms of treatment:

indications of radiotherapy

Contraindications of radiotherapy

side effects cont.

side effects

TirednessHair loss Nausea and vomiting Diarrhea Skin changes (peeling, dryness, irritation) Anemia (low red blood cell count).

oral complications

Radiation therapy can directly damage oral cavity including:1) Breakdown of tissue in the area that receives radiation. 2) Breakdown of bone in the area that receives radiation. 3) Fibrosis of muscle in the area that receives radiation. 4) Inflamed mucous membranes in the mouth. 5) (mucositis) Taste changes:change in sweet, sour, bitter, and salty tastes( usually its permanent damage to taste buds). 6) Bleeding: lower the platlet count, mild (small red spots on the lips, soft palate, or bottom of the mouth) or severe, especially at the gum line and from ulcers in the mouth.

oral complications cont.

general oral management

Dental management

extractions should be done 14–21 days earlier to avoid the risk of osteoradionecrosis (ORN). All major surgeries should be performed 4–6 weeks in advanced to start of radiotherapy.Osteoradionecrosis may be prevented by extracting these teeth at least 2 weeks before radiotherapy, (periodontally involved teeth, unerupted teeth). Prevention of dental caries and periodontal disease and their sequelae can prevent ORN in most cases. If teeth are extracted after radiotherapy care should be given to use atraumatic technique, smooth sharp edges of bone, and avoid reflection of the periosteum if possible. The prevalence of ORN following a dental extraction was 21.9%. Dental extraction of more than five years after RT. (2021) Extremely mobile periodontally compromised teeth can be safely removed with minimal risk of developing ORN.

It may be advisable to place the patient on prophylactic antibiotics for one week after extraction to reduce the risk of infection.

Thanks!