SGD

Question 1

What is the primary aim of radiation therapy?

Answer 1

To deliver a precisely measured dose of irradiation to a defined tumor volume with minimal damage to surrounding tissue.

The intents of radiation therapy include curative, adjuvant, palliative, and neoadjuvant.

Question 2

What are the four intents of radiation therapy?

Answer 2

• Curative
• Adjuvant
• Palliative
• Neoadjuvant

These intents guide the application of radiation therapy in treatment plans.

Question 3

What types of radiation are used in radiation therapy?

Answer 3

• Photons
• Electrons
• Protons
• α particles
• Neutrons

Photons are the primary modality for therapeutic irradiation, especially in gynecologic carcinomas.

Question 4

Which type of radiation therapy is primarily used for superficial tumors?

Answer 4

Electrons

Electrons are suitable only for superficial tumors, such as skin cancers.

Question 5

What is the ‘ALARA’ principle in radiation exposure?

Answer 5

‘As Low As Reasonably Achievable’

This principle emphasizes minimizing radiation exposure to patients and staff.

Question 6

What is the SI unit of radiation-absorbed dose?

Answer 6

Gray (Gy)

1 Gy is equivalent to 100 cGy or 100 rads.

Question 7

What is ionization in the context of radiation therapy?

Answer 7

When an outer shell electron is stripped from an atom, leaving a positive charge.

This process can cause direct DNA damage.

Question 8

What are the two mechanisms of radiation action on cells?

Answer 8

• Direct Action
• Indirect Action

Direct action involves direct DNA damage, while indirect action produces free radicals that diffuse and damage critical targets.

Question 9

What is the Compton Effect?

Answer 9

The major interaction of photons in tissue used in modern radiotherapy.

It involves the scattering of photons, which is significant in radiation therapy.

Question 10

Define ‘half-life’ in the context of radioactive decay.

Answer 10

The time required for a radionuclide to disintegrate to half its original activity.

The half-life is important for understanding the longevity of radioactive materials used in therapy.

Question 11

What does the Inverse Square Law state?

Answer 11

Dose of radiation at a given point is inversely proportional to the square of the distance from the source of radiation.

This principle is particularly important in brachytherapy.

Question 12

What is the significance of tumor volume in radiation therapy?

Answer 12

The smaller the tumor volume, the less radiation is required to destroy all cells.

Larger tumors may require higher doses due to increased cell numbers and radioresistance.

Question 13

What is the ‘4R’s of Radiobiology’?

Answer 13

• Repair
• Reoxygenation
• Redistribution
• Repopulation

These factors influence the effectiveness of radiation therapy.

Question 14

What is the purpose of radiosensitizers in radiation therapy?

Answer 14

To increase the ability of radiation to cause permanent, lethal damage to tumor cells.

They help enhance the effectiveness of radiation by modifying cellular responses.

Question 15

What does ‘IMRT’ stand for?

Answer 15

Intensity-Modulated Radiation Therapy

IMRT uses smaller beams and can change the strength of beams to deliver higher doses to certain parts of the tumor.

Question 16

What is the typical dose for definitive EBRT in cervical cancer?

Answer 16

45 Gy (40-50 Gy), followed by brachytherapy with an additional 30-40 Gy.

The total dose may vary based on tumor size and patient factors.

Question 17

What is brachytherapy?

Answer 17

A form of radiation therapy where a radioactive source is placed inside or near the tumor.

It allows for high doses of radiation to the tumor while minimizing exposure to surrounding healthy tissue.

Question 18

What is the purpose of image-guided radiation therapy (IGRT)?

Answer 18

To use imaging during radiotherapy sessions to improve precision.

IGRT enhances the accuracy of radiation delivery to the target area.

Question 19

What is a common practice during EBRT for cervical cancer patients?

Answer 19

Concurrent platinum-based chemotherapy is usually given during EBRT.

This combination aims to enhance treatment effectiveness.

Question 20

True or False: Hypoxic cells are more sensitive to radiation than cells with normal oxygen tension.

Answer 20

False

Hypoxic cells are more resistant to the effects of radiation.

Question 21

What is intraoperative radiation therapy (IORT)?

Answer 21

Delivers a single, highly focused dose of radiation to an at-risk tumor bed or isolated unresectable residual disease during an open surgical procedure.

Useful in patients with recurrent disease within a previously radiated volume.

Question 22

What are the modes of Brachytherapy?

Answer 22

• Intracavitary irradiation
• Interstitial irradiation

Intracavitary uses applicators loaded with radioactive materials, while interstitial involves removable needles or permanent isotope implants.

Question 23

What is the typical dose for pelvic radiation therapy in high-risk factors for cervical cancer?

Answer 23

Pelvic RT 4500 to 5040 cGy in 180 cGy per fraction.

This is the recommended dose for patients with positive margins, positive lymph nodes, or parametrial involvement.

Question 24

What are common short-term side effects of radiation therapy?

Answer 24

• Fatigue
• Abdominal pain
• Diarrhea
• Nausea and vomiting
• Skin changes
• Radiation cystitis
• Vaginal pain
• Menstrual changes/Menopause
• Low blood counts

These side effects can occur during or shortly after radiation treatment.

Question 25

What are long-term side effects of radiation therapy?

Answer 25

* Vaginal stenosis * Vaginal dryness * Rectal bleeding/rectal stenosis * Chronic cystitis/vesicovaginal fistula * Weakened bones * Lymphedema ## Footnote Long-term effects can develop years after treatment.

Question 26

What is the maximum dose for vaginal mucosa in radiation therapy?

Answer 26

20,000 to 25,000 cGy. ## Footnote This dose is critical for avoiding damage to the vaginal mucosa.

Question 27

What is the dose required to double the spontaneous mutation rate due to radiation?

Answer 27

100 cGy. ## Footnote This dose is significant in understanding genetic effects of radiation exposure.

Question 28

What are potential fetal effects of radiation exposure during pregnancy?

Answer 28

* Intrauterine and extrauterine growth restriction * Embryonic, fetal, or neonatal death * Gross congenital malformations ## Footnote The impact varies depending on the age of gestation at the time of exposure.

Question 29

What is the recommended fetal dose for entire gestation?

Answer 29

0.5 cGy. ## Footnote This recommendation is crucial for minimizing fetal risk during radiological procedures.

Question 30

What is the role of chemotherapy as a radiosensitizer in cervical cancer treatment?

Answer 30

Chemotherapy is used alongside radiation to enhance the effectiveness of the treatment. ## Footnote This approach is particularly noted in the context of adjuvant therapy.

Question 31

What is the significance of brachytherapy in the treatment of locally advanced cervical cancer?

Answer 31

Associated with improved survival compared with IMRT or SBRT as a boost. ## Footnote Brachytherapy remains a critical component despite declining utilization rates.

Question 32

What is the typical brachytherapy dose for locally advanced cervical cancer?

Answer 32

Dose required depends on the size of the involved node, typically 5500-6000 cGy for involved nodes. ## Footnote This is part of a comprehensive treatment plan including pelvic radiation.

Question 33

What are the recommended doses for adjuvant radiation therapy in intermediate risk factors?

Answer 33

* Pelvic RT 4500 to 5040 cGy in 180 cGy per fraction * Pelvic RT 4000 to 4400 cGy in 200 cGy per fraction ## Footnote These doses are tailored based on the patient's risk factors.

Question 34

What is the conclusion regarding the addition of Cisplatin-based chemotherapy to radiation therapy?

Answer 34

Improves progression-free survival (PFS) and overall survival (OS) in high-risk, early-stage cervical cancer patients. ## Footnote This conclusion is based on studies comparing RT alone with RT + CT.

Question 35

When is brachytherapy indicated for cervical cancer patients?

Answer 35

Indicated for patients with locally advanced cervical cancer, particularly those with stage IB3, IIA2 - IVA. ## Footnote Concurrent chemotherapy and pelvic EBRT + Brachytherapy is the preferred approach.

Question 36

What imaging techniques are used in brachytherapy planning?

Answer 36

* 2D/Point-based (AP and lateral films) * 3D imaging techniques ## Footnote These techniques help in accurately delivering doses to target areas.

Question 37

What is the recommendation regarding adjuvant hysterectomy after radiation therapy?

Answer 37

Not routinely recommended due to no improvement in survival outcomes and increased toxicity. ## Footnote This highlights the importance of evaluating treatment options carefully.

Question 38

What is the significance of the study comparing IMRT and 3D RT?

Answer 38

Pelvic IMRT was associated with significantly less GI and urinary toxicity compared to standard RT. ## Footnote This finding underscores the benefits of advanced radiation techniques.

Question 39

What is the optimal imaging for brachytherapy treatment planning?

Answer 39

MRI and CT are standard for brachytherapy treatment planning ## Footnote MRI is better for soft tissue definition and visualization of cervix and residual disease, while CT may overestimate tumor width.

Question 40

What is Point A in brachytherapy planning?

Answer 40

Point A is located where the uterine artery and ureter cross: 2 cm superior and 2 cm lateral to external os.

Question 41

What is Point B in brachytherapy planning?

Answer 41

Point B is located 5 cm lateral to midline at the level of Point A, corresponding to pelvic sidewall/obturator lymph nodes.

Question 42

What is the significance of EQD2 in brachytherapy?

Answer 42

EQD2 is the dose calculation to an equivalent dose of 2 Gy with an α-to-β ratio of 10.

Question 43

What is the recommended brachytherapy regimen in combination with EBRT for cervical cancer?

Answer 43

Brachytherapy regimens are given in combination with 4500 cGy EBRT.

Question 44

What is the role of supplemental interstitial needles in brachytherapy?

Answer 44

Supplemental interstitial needles may help optimize dose distributions while meeting normal organs at risk constraints.

Question 45

What is D2cc in brachytherapy?

Answer 45

D2cc is the minimal dose to the 2 cm³ (2 mL) of the organ at risk receiving the maximal dose.

Question 46

True or False: Vaginal stenosis is correlated with the combined EBRT and brachytherapy dose to the rectovaginal point.

Answer 46

True ## Footnote The EMBRACE study shows a correlation, with a 20% risk at 6500 cGy.

Question 47

What is the definition of the recto-vaginal point in brachytherapy?

Answer 47

The recto-vaginal point is defined 5 mm posterior to the vaginal mucosa from the center of the vaginal sources.

Question 48

What imaging technique can reduce the risk of uterine perforation during brachytherapy?

Answer 48

Real-time guidance with transabdominal or transrectal ultrasound.

Question 49

What are the two types of planning for brachytherapy?

Answer 49

* 2D/Point-based (AP and lateral Films) * Volumetric/3D (CT/MRI)

Question 50

Fill in the blank: The dose calculation to an equivalent dose of 2 Gy with an α-to-β ratio of 10 is known as _______.

Answer 50

EQD2

Question 51

What is the advantage of using MRI over CT for brachytherapy?

Answer 51

MRI provides better soft tissue definition and easier visualization of the cervix and residual disease.

Question 52

What is the maximum dose constraint for the organ at risk in brachytherapy?

Answer 52

There will be occasions when exceeding maximum constraints is necessary to adequately treat targets, according to clinical judgment.