Section 4: Childhood Cancer Treatment- Radiation Therapy

Front 1

What are some of the roles that radiation therapy can play in the treatment of childhood cancer?

Back 1

- combo w/chemo, biotherapy, or surgery
- independently used
- many solid tumors & lymphomas are radiosensitive
- Leukemia/lymphoma CNS disease treatment
- emergent use to treat tumors that are causing problems like superior vena cava syndrome, spinal-cord compression or airway compromise
- Palliation

Front 2

How does radiation therapy treat cancer?

Back 2

High-energy particles or waves are used to destroy cancer cells by damaging their DNA, thereby preventing cell replication

Front 3

In what cell cycle is radiation therapy most effective?

Back 3

M and G2 phases when cells are rapidly dividing & are well oxygenated

Front 4

Why is intracellular oxygen so important to maximize the radiation therapy effect?

Back 4

Oxygen is needed to produce free radicals when lead to the chemical change that results in cell destruction

Front 5

What 2 other aspects of radiation treatment influence the response of cells to radiation therapy?

Back 5

Dose rate
Fractionation (daily administration divided in fractions)

Front 6

Is fractionated radiation less toxic to healthy surrounding tissues?

Back 6

Yes

Front 7

What does the RT planning process involve?

Back 7

1. Meeting w/radiation oncologist
2. Simulation using CT or MRI to identify specific radiation fields
3. Planning for immoblization (relaxation and/or anesthesia)

Front 8

What are the 7 different methods of RT delivery?

Back 8

1. External Beam
2. Brachytherapy
3. Conformal
4. IMRT (Intensity Modulated RT)
5. IORT (Intraoperative RT)
6. Proton
7. Sterotactic Radiosurgery

Front 9

What are the common types of external beam radiation?

Back 9

X-rays
Gamma rays
Electrons

Front 10

How does an external beam radiation treat the cancer?

Back 10

well-defined, 2-dimensional beam of radiation is aimed at specific anatomic site or tumor

Front 11

What is brachytherapy radiation treatment?

Back 11

temporary or permanent implantation of radioactive seeds or pellets directly into a body cavity, tissue, or skin surface

Front 12

What type of dose does brachytherapy radiation provide?

Back 12

A prescribed dose of radiation to a localized area alone or in combo w/external beam RT

Front 13

What are some common pediatric cancers that use brachytherapy radiation as treatment?

Back 13

1. Soft-tissue tumors
2. Retinoblastoma
3. CNS tumors

Front 14

What is conformal RT?

Back 14

3D radiation being delivered to contours of a tumor precisely to "conform" to affected area
(sparing healthy tissue)

Front 15

How does Intensity Modulated RT differ from other forms of RT?

Back 15

- it delivers varying intensities of radiation beams
- it modulates for high & low doses in same field
- starts w/high dose at target area, and lower doses around (sparing healthy tissue)
- can treat multiple sites at one time

Front 16

How is IORT (intraoperative) delivered?

Back 16

- as a single dose during surgery to exposed tumor, tumor bed & surrounding tissues

Front 17

What does IORT ensure in regards to treatment?

Back 17

that patient receives radiation only to affected site, preserving healthy tissue
- single dose delivery has biological effect of several daily fractions

Front 18

What is proton RT?

Back 18

Type of external beam radiation
- uses proton-charged particle to deliver energy over short distance

Front 19

What does Bragg peak refer to when talking about proton RT?

Back 19

the short distances that the proton-charged particles are delivered over
(low dose delivered in front of tumor, high dose delivered to entire tumor, minimal exit radiation

Front 20

What is the advantage of using proton RT?

Back 20

it can be directed to conform to tumor, minimizing radiation to normal tissue

Front 21

What is stereotactic radiosurgery?

Back 21

- a high-dose of radiation delivered via a focused beam to a small, well-circumscribed area of tumor

Front 22

How is stereotactic radiotherapy different than stereotactic radiosurgery?

Back 22

Stereotactic Radiotherapy is carried out over multiple fractions and can treat larger tumor volumes

Front 23

What does the concept of minimum tissue tolerance dose (TTD) refer to regarding radiation?

Back 23

the probability of a radiation-induced complication after a dose of radiation

Front 24

Do different organs have different TTD (tissue tolerance dose) values?

Back 24

Yes

Front 25

What other factors are related to the risk of side effects?

Back 25

- location of radiation field
- age of the child (younger = more vulnerable)
- adjuvant chemotherapy

Front 26

Do acute early and late side effects of radiation treatment usually resolve once treatment has been completed?

Back 26

Yes
- they are usually limited to area of body being irradiated

Front 27

As a general side effect when does fatigue usually begin?

Back 27

- can begin several weeks into RT, but can persist for several months after treatment completed

Front 28

Myelosuppression can occur specifically after RT to what locations?

Back 28

-pelvis
-sternum
-long bones
(also when chemo is given w/RT)

Front 29

Why is RT not recommended for children under age 3years?

Back 29

Myelination is incomplete at this age, and giving RT before it is complete can cause significant neurocognitive & functional impairment

Front 30

What are some common CNS side effects with RT to the brain?

Back 30

Brain: HA, n/v, somnolence

Front 31

What are some common CNS side effects with RT to the spinal cord?

Back 31

Spinal: radiation myelopathy (electrical shock sensation after neck flexion- usu resolves w/out treatment)

Front 32

What characterizes radiation somnolence syndrome?

Back 32

fatigue & slowed mentation
- occurs few weeks to months after cranial XRT
- usu. resolves w/out intervention in 4-6 weeks.

Front 33

What side effect of the digestive system may occur after the first or second RT treatment?

Back 33

-Swollen & painful salivary glands
-thickening of saliva
-decreased volume of saliva (xerostomia = dry mouth)

Front 34

What side effect of the digestive system can occur and last for months to years?

Back 34

Loss or change of taste

Front 35

What can one infer if the amylase is elevated after radiation to the parotid gland?

Back 35

Parotitis (it resolves quickly)

Front 36

What dental side effects can RT treatment cause?

Back 36

- dental caries (decr'd saliva & bacteria)
- microdontia (small teeth)
(developing teeth at highest risk)

Front 37

At what dose does erythema of oral mucosa and dysphagia typically occur?

Back 37

20Gy

Front 38

At what dose does desquamation occur in the oral mucosa?

Back 38

40Gy
- regeneration of oral mucosa occurs about 2-3 weeks after treatment

Front 39

Are ulcers of the stomach common in pediatric patients treated with RT?

Back 39

No, ulcers occur at 45Gy, and this is a rare, if ever, pediatric dose

Front 40

What chemotherapy used in combination w/RT increased hepatic radiosensitivity?

Back 40

Adriamycin (doxorubicin)
Actinomycin-D (dactinomycin)
Cytoxan (cyclophosphamide)
Oncovin (Vincristine)

Front 41

What side effect of the large intestines(colon) can occur with RT doses greater than 60Gy?

Back 41

Persistent proctitis
rectal ulceration
rectal stenosis

Front 42

What symptoms are characteristic of radiation pneumonitis?

Back 42

Dyspnea
Dry cough
Tachypnea
Tachycardia
Pulmonary infiltrates on X-ray

Front 43

What RT dose can cause radiation pneumonitis?

Back 43

>20Gy to both lungs
(TTD of whole lung is 20Gy)

Front 44

What combination chemotherapy with RT increases the incidence of radiation pneumonitis?

Back 44

Bleomycin (Blenoxane)
Dactinomycin (Actinomycin-D)

Front 45

What patients have an increased incidence of radiation-induced heart disease?

Back 45

Those given:
- high dose radiation
- combo chemo w/doxorubicin

Front 46

What does radiation-induced heart disease consist of?

Back 46

Fibrous thickening of pericardium
s/s = pericardial effusion or pericarditis
(can occur 2 month to years after RT)

Front 47

What side effect of RT can occur 6-12 months after treatment and present similar to nephrotic syndrome?

Back 47

Acute Radiation Nephritis (hypertension and proteinuria)

Front 48

What are the symptoms of acute radiation cystitis?

Back 48

urinary frequency
dysuria

Front 49

Why is RT not given to the bladder concurrently when cyclophosphamide therapy is being used?

Back 49

Already very high risk of hemorrhagic cystitis with cyclophosphamide

Front 50

What does of RT can cause azoospermia up to 5 years?

Back 50

4-6 Gy

Front 51

At what dose of RT can a female experience sterilization of her ovaries?

Back 51

Doses >6Gy

Front 52

T or F: Even when little or no bone marrow is included in the RT field, the peripheral lymphocyte count can fall

Back 52

True.
- circulating lymphocytes & pre-cursors to platelets are acutely sensitive to effects of RT.
- WBC (other than lymphocytes) and platelets are less sensitive

Front 53

AT what dose of RT is bone growth stopped & hypoplastic changes in muscle and tissue are noted?

Back 53

>20 Gy

Front 54

At what dose of RT does moist desquamation occur of the skin?

Back 54

50Gy
- resolves in a few weeks