Radiation Oncology Basics Practice Questions

Q: What is the standard radiation dose for treating Hodgkin lymphoma?

20-30 Gy. **Explanation:** The treatment paradigm for Hodgkin Lymphoma (HL) has shifted significantly toward **Combined Modality Therapy (CMT)**, which utilizes chemotherapy followed by low-dose **Involved-Site Radiation Therapy (ISRT)**. **Why 20-30 Gy is correct:** Hodgkin Lymphoma is highly radiosensitive. Modern protocols (like ABVD chemotherapy followed by radiation) have shown that lower doses are sufficient for disease control while minimizing long-term toxicities. * For patients with **favorable early-stage HL** who achieve a complete response on PET scan, the standard dose is **20 Gy**. * For **unfavorable early-stage HL** or those with a partial response, the dose is typically **30 Gy**. Thus, the range of 20-30 Gy represents the current standard of care. **Why other options are incorrect:** * **30-40 Gy:** This was the historical standard (Extended Field Radiation) used before the era of modern chemotherapy. Currently, doses above 30 Gy are reserved only for bulky disease or salvage therapy. * **40-60 Gy:** These high doses are typically used for solid epithelial tumors (e.g., Squamous Cell Carcinoma of the head and neck). Using such doses in HL would lead to unacceptable risks of secondary malignancies and cardiovascular disease. **NEET-PG High-Yield Pearls:** * **Radiosensitivity:** Lymphocytes are among the most radiosensitive cells in the body (Law of Bergonie and Tribondeau). * **Field Evolution:** The field has evolved from **Mantle Field** (historical) → **Involved Field (IFRT)** → **Involved Site (ISRT)** (current standard). * **Late Complications:** The primary goal of using 20-30 Gy is to reduce the risk of secondary breast cancer, lung cancer, and coronary artery disease.

Q: For radiotherapy, an isotope is placed in or around the cancer site. What is this called?

Brachytherapy. **Explanation:** The correct answer is **Brachytherapy**. This term is derived from the Greek word *'brachys'*, meaning 'short distance.' In this modality, radioactive sources (isotopes) are placed directly into (interstitial), inside a body cavity (intracavitary), or on the surface of the tumor. This allows for a high dose of radiation to be delivered to the tumor while rapidly sparing the surrounding healthy tissues due to the **Inverse Square Law**. **Analysis of Incorrect Options:** * **Teletherapy (Option B):** Derived from *'tele'*, meaning 'far.' This refers to radiation delivered from a source located at a distance from the body (usually 80–100 cm). * **External Beam Radiotherapy (EBRT) (Option C):** This is a synonym for Teletherapy. It uses machines like Linear Accelerators (LINAC) or Cobalt-60 to aim high-energy beams at the cancer from outside the body. * **Intensity Modulated Radiotherapy (IMRT) (Option D):** An advanced form of EBRT that manipulates the intensity of individual beams to conform precisely to the tumor shape, minimizing damage to adjacent organs at risk (OARs). **High-Yield Clinical Pearls for NEET-PG:** * **Common Isotopes:** Cesium-137 (Cervical cancer), Iridium-192 (Breast/Prostate), and Iodine-125 (Permanent seeds for Prostate). * **Manchester System:** A classic dosage system used specifically for Brachytherapy in Carcinoma Cervix. * **Advantage:** Brachytherapy provides a superior "biological dose" because the radiation source moves with the organ (e.g., the uterus), unlike external beams.

Q: Which of the following is true regarding brachytherapy?

Brachytherapy is used in carcinoma of the cervix.. **Explanation:** **Brachytherapy** (derived from the Greek word *brachys*, meaning "short") is a form of radiotherapy where a sealed radioactive source is placed inside or in close proximity to the area being treated. **Why Option C is Correct:** Brachytherapy is a cornerstone in the management of **Carcinoma Cervix**. It allows for the delivery of a very high dose of radiation to the tumor (via intracavitary applicators like Tandem and Ovoids) while sparing adjacent critical organs like the bladder and rectum. It is typically used as a "boost" after External Beam Radiation Therapy (EBRT). **Why Other Options are Incorrect:** * **Option A:** Brachytherapy follows the **Inverse Square Law**, meaning the radiation intensity decreases rapidly as the distance from the source increases. This results in **highly non-homogeneous** dose distribution (high dose near the source, low dose further away), which is actually its primary clinical advantage. * **Option B:** Brachytherapy is distinct from **Teletherapy** (External Beam Radiation). In teletherapy, the radiation source is at a distance from the patient (e.g., Linear Accelerator or Cobalt-60 unit), whereas in brachytherapy, the source is internal. **High-Yield Clinical Pearls for NEET-PG:** * **Common Isotopes:** Iridium-192 (most common for HDR), Cesium-137, Iodine-125 (permanent seeds for prostate), and Cobalt-60. * **Types:** * *Intracavitary:* Cervix, Endometrium. * *Interstitial:* Breast, Soft tissue sarcoma, Tongue. * *Surface Mold:* Skin cancers. * *Intraluminal:* Esophagus, Bronchus. * **Advantage:** It provides a high "therapeutic ratio" by delivering a localized ablative dose with a rapid dose fall-off.

Q: Concomitant chemoradiotherapy is indicated in all of the following conditions EXCEPT:

T2 N0 M0 glottic cancer. **Explanation:** The core concept tested here is the standard of care for various malignancies. **Concomitant Chemoradiotherapy (CCRT)** is used as a primary treatment for advanced or aggressive tumors to improve local control and survival. **Why Option C is the Correct Answer:** For **Early Glottic Cancer (T1-T2, N0, M0)**, the standard of care is **single-modality therapy**—either radiotherapy alone or organ-preserving surgery (like CO2 laser excision). CCRT is not indicated because single-modality treatment achieves excellent cure rates (85-95%) while preserving voice quality. Adding chemotherapy would increase toxicity without providing a significant survival benefit in early-stage disease. CCRT is reserved for advanced laryngeal cancers (T3-T4) as an organ-preservation strategy. **Analysis of Incorrect Options:** * **Stage III B Ca Cervix:** CCRT (Cisplatin-based) is the gold standard for locally advanced cervical cancer (Stage IB3 to IVA). * **T2 N0 M0 Anal Cancer:** The **Nigro Protocol** (CCRT with 5-FU and Mitomycin-C) is the definitive treatment for squamous cell carcinoma of the anal canal, avoiding the need for permanent colostomy. * **T1 N2 M0 Nasopharyngeal Cancer:** Because of its high radiosensitivity and chemosensitivity, CCRT is the standard treatment for all nasopharyngeal cancers except Stage I (T1N0). **Clinical Pearls for NEET-PG:** * **Nigro Protocol:** Definitive CCRT for Anal Canal Cancer. * **Cisplatin:** The most common radiosensitizer used in CCRT for Head & Neck and Cervical cancers. * **Early Glottic Cancer:** Radiotherapy and Surgery are equally effective; the choice depends on patient preference and functional outcome.

Q: All of the following are used in interstitial brachytherapy except?

Co-60. **Explanation:** The core concept in interstitial brachytherapy is the placement of radioactive sources directly into the tumor tissue. This requires sources that are small, flexible, and have a high specific activity to deliver a localized dose while minimizing damage to surrounding healthy tissues. **Why Co-60 is the correct answer:** **Cobalt-60 (Co-60)** is primarily used in **External Beam Radiation Therapy (EBRT)** via Telecobalt units. It is generally **not used for interstitial brachytherapy** because it has a very high energy (mean 1.25 MeV), which makes shielding difficult within the body, and it has a relatively large source size. While Co-60 can be used in some Intracavitary applications (like modern HDR units), it is not a standard choice for interstitial implants. **Analysis of other options:** * **Ir-192 (Iridium):** The most commonly used isotope for temporary interstitial brachytherapy (HDR and LDR). Its high specific activity allows for very small source sizes (wires/seeds), making it ideal for breast, head, and neck cancers. * **Au-198 (Gold):** Historically used as permanent interstitial "seeds" (e.g., for prostate or tongue) due to its short half-life (2.7 days), allowing the source to be left in the body permanently. * **Cs-137 (Cesium):** Traditionally used for LDR interstitial and intracavitary (cervix) brachytherapy. While being phased out by Ir-192, it remains a classic example of a brachytherapy source. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Brachytherapy:** Ir-192 is currently the most versatile and widely used isotope. * **Permanent Implants:** Iodine-125 (I-125) and Palladium-103 (Pd-103) are the modern choices for permanent prostate brachytherapy. * **Half-life Fact:** Ir-192 has a half-life of **74 days**, whereas Co-60 has a half-life of **5.26 years**. * **Ophthalmic Applicators:** Ruthenium-106 and Iodine-125 are used for choroidal melanoma (plaque brachytherapy).

Q: Which of the following is NOT a brachytherapy technique used for carcinoma of the cervix?

New York technique. **Explanation:** In the treatment of Carcinoma Cervix, **Brachytherapy** (internal radiation) is a cornerstone of therapy. Historically, three major classical systems were developed based on different dose distribution philosophies and loading patterns. 1. **Why Option B is Correct:** There is no established **"New York technique"** in the classical nomenclature of cervical brachytherapy. This is a distractor option. 2. **Why Other Options are Incorrect:** * **Stockholm Technique (Option D):** One of the oldest methods, it uses an "intermittent" high-intensity loading approach. It utilizes a central tandem and a flat vaginal applicator (box) with high doses delivered in 2–3 sessions over a few weeks. * **Paris Technique (Option A):** Developed at the Curie Institute, this technique uses a "continuous" low-dose-rate approach. It is characterized by using a tandem and two vaginal cylinders (colpostats) joined by a spacer (cork). * **Manchester Technique (Option C):** This is the most high-yield system for exams. It evolved from the Paris system and introduced the concept of **Point A and Point B** to standardize dosage. It uses a fixed relationship between the intrauterine tandem and vaginal ovoids. **High-Yield Clinical Pearls for NEET-PG:** * **Point A:** Located 2 cm superior to the lateral vaginal fornix and 2 cm lateral to the uterine canal. It represents where the uterine artery crosses the ureter. * **Point B:** Located 3 cm lateral to Point A (5 cm from the midline). It represents the pelvic wall and lymph nodes (Obturator nodes). * **ICRU 38/89:** Modern brachytherapy has shifted from these classical systems toward Image-Guided Adaptive Brachytherapy (IGABT) using MRI-based volume planning (HR-CTV).

Q: What grade of mucositis is characterized by large painful ulcers?

Grade 3. Oral mucositis is a common and debilitating side effect of chemotherapy (e.g., Methotrexate, 5-Fluorouracil) and radiotherapy. The World Health Organization (WHO) grading system is the gold standard for classification, focusing on the presence of ulcers and the patient's ability to eat. **Explanation of the Correct Answer:** * **Grade 3 (Correct):** This stage is characterized by **extensive, painful ulcerations and erythema**. Clinically, the patient is **unable to swallow solid food** and is restricted to a liquid diet. The presence of "large painful ulcers" that significantly impair oral intake is the hallmark of Grade 3. **Analysis of Incorrect Options:** * **Grade 1:** Characterized by soreness and erythema (redness) of the mucosa, but **no ulcers** are present. * **Grade 2:** Characterized by erythema and **small, isolated ulcers**. The patient can still swallow solid food despite the discomfort. * **Grade 4:** This is the most severe stage where oral intake is impossible. The patient requires **total parenteral nutrition (TPN)** or enteral feeding due to the severity of the lesions. **NEET-PG High-Yield Pearls:** * **Drug Association:** Methotrexate is a classic cause of mucositis. **Folinic acid (Leucovorin)** is used as a "rescue" to prevent/limit this toxicity. * **Management:** Palifermin (Recombinant Human Keratinocyte Growth Factor) is used to reduce the incidence and duration of severe mucositis in patients receiving high-dose chemotherapy. * **Quick Recall Table:** * Grade 1: Erythema only. * Grade 2: Ulcers + Can eat solids. * Grade 3: Ulcers + Liquid diet only. * Grade 4: No oral intake possible (TPN required).

Q: What is the best investigation for planning radiotherapy for carcinoma of the esophagus?

PET scan. **Explanation:** The correct answer is **PET scan (Positron Emission Tomography)**, specifically PET-CT, which is now considered the gold standard for planning radiotherapy in esophageal carcinoma. **Why PET Scan is Correct:** Radiotherapy planning requires precise **Target Volume Delineation**. PET scans utilize 18F-FDG uptake to differentiate viable tumor tissue from peritumoral edema, atelectasis, or normal tissue. This functional imaging allows for more accurate identification of the "Gross Tumor Volume" (GTV) and involved lymph nodes compared to anatomical imaging alone. Studies show that PET-CT significantly alters the radiation field in up to 30-40% of patients, preventing "geographical miss" of the tumor and sparing healthy surrounding tissues (like the heart and lungs) from unnecessary radiation. **Why Other Options are Incorrect:** * **CT Scan:** While CT is excellent for anatomical mapping and dose calculation, it often fails to distinguish the exact longitudinal extent of the tumor or identify small involved lymph nodes, leading to less precise targeting. * **Ultrasound:** Transabdominal ultrasound has no role in esophageal staging or RT planning. While **Endoscopic Ultrasound (EUS)** is the best for T and N staging, it cannot be used for radiotherapy contouring or detecting distant metastasis. * **MRI:** MRI provides superior soft-tissue contrast but is not the primary modality for RT planning in the esophagus due to motion artifacts (respiratory/cardiac) and lack of standardized protocols compared to PET-CT. **Clinical Pearls for NEET-PG:** * **Best for T and N staging:** Endoscopic Ultrasound (EUS). * **Best for M (Metastasis) staging:** PET-CT. * **Best for RT Planning:** PET-CT. * **Initial investigation of choice:** Barium swallow (shows "Rat-tail" or "Bird-beak" appearance depending on pathology). * **Definitive diagnosis:** Endoscopic biopsy.

Q: Which of the following is used in External Beam Radiotherapy?

LINAC. ### Explanation **Correct Answer: D. LINAC** **Concept:** External Beam Radiotherapy (EBRT) involves delivering high-energy radiation from a source outside the patient’s body. The **Linear Accelerator (LINAC)** is the most commonly used device for EBRT. It uses microwave technology to accelerate electrons to near light speed, which then collide with a heavy metal target to produce high-energy X-rays (photons) or are used directly as electron beams to treat tumors. **Analysis of Incorrect Options:** * **A. I-131 (Iodine-131):** This is a radioisotope used primarily in **Systemic Radionuclide Therapy**. It is administered orally for the treatment of hyperthyroidism and differentiated thyroid cancer. * **B. P-32 (Phosphorus-32):** This is a pure beta-emitter used in **Internal Radiotherapy**. Historically, it was used for polycythemia vera and is currently used for intracavitary treatment (e.g., cystic brain tumors) or pleurodesis. * **C. I-125 (Iodine-125):** This is a low-energy gamma emitter used primarily in **Brachytherapy** (permanent seed implants), most commonly for localized prostate cancer. **Clinical Pearls for NEET-PG:** * **LINAC vs. Cobalt-60:** While Cobalt-60 was the traditional EBRT source (using Gamma rays), LINAC is now preferred because it provides higher energy, better skin-sparing effects, and does not involve a radioactive source that decays. * **Teletherapy:** EBRT is also known as Teletherapy (source-to-surface distance is usually 80–100 cm). * **Brachytherapy:** Treatment where the source is placed inside or in close proximity to the tumor (short distance). * **Common EBRT Modalities:** 3D-CRT, IMRT (Intensity Modulated Radiotherapy), and VMAT (Volumetric Modulated Arc Therapy) are all delivered via a LINAC.

Q: Whole body radiation is indicated in which of the following conditions?

Bone marrow transplantation. **Explanation:** **Total Body Irradiation (TBI)** is a form of radiotherapy where the entire body is exposed to ionizing radiation. The primary clinical indication for TBI is as part of the **conditioning regimen for Bone Marrow Transplantation (BMT)**, particularly in hematologic malignancies like leukemia or lymphoma. **Why BMT is correct:** TBI serves two critical purposes in BMT: 1. **Myeloablation:** It destroys the patient's own diseased bone marrow and residual cancer cells. 2. **Immunosuppression:** It suppresses the host’s immune system to prevent the rejection of the donor’s stem cells (Graft-versus-Host prevention). **Why other options are incorrect:** * **Advanced Head & Neck Tumors:** These are treated with **Localized External Beam Radiation Therapy (EBRT)** or Brachytherapy to spare surrounding healthy tissues like the spinal cord and salivary glands. * **Medulloblastoma:** This requires **Craniospinal Irradiation (CSI)**. Because this tumor spreads via CSF, the entire brain and the complete length of the spinal cord are irradiated, but not the whole body. * **Mycosis Fungoides:** This is a cutaneous T-cell lymphoma treated with **Total Electron Beam Skin Irradiation (TSEI)**. Electrons are used because they have low tissue penetration, treating only the skin surface while sparing internal organs. **High-Yield Clinical Pearls for NEET-PG:** * **Dose:** TBI is usually delivered in fractions (12–15 Gy total) to reduce toxicity. * **Critical Organs:** The **lungs** are the dose-limiting organs in TBI; shields are used to prevent radiation pneumonitis. * **Late Complication:** Cataract formation is a common long-term side effect of TBI.

Question 1

What is the standard radiation dose for treating Hodgkin lymphoma?

Accepted Answer

20-30 Gy

Answer

30-40 Gy

Answer

40-50 Gy

Answer

50-60 Gy

Question 2

For radiotherapy, an isotope is placed in or around the cancer site. What is this called?

Accepted Answer

Brachytherapy

Answer

Teletherapy

Answer

External beam therapy

Answer

Intensity modulated radiotherapy

Question 3

Which of the following is true regarding brachytherapy?

Accepted Answer

Brachytherapy is used in carcinoma of the cervix.

Answer

Brachytherapy always gives homogeneous radiation.

Answer

Brachytherapy is the same as teletherapy.

Answer

All of the above.

Question 4

Concomitant chemoradiotherapy is indicated in all of the following conditions EXCEPT:

Accepted Answer

T2 N0 M0 glottic cancer

Answer

Stage III B Ca cervix

Answer

T2 N0 M0 anal cancer

Answer

T1 N2 M0 nasopharyngeal cancer

Question 5

All of the following are used in interstitial brachytherapy except?

Accepted Answer

Co-60

Answer

Ir-192

Answer

Au-198

Answer

Cs-137

Question 6

Which of the following is NOT a brachytherapy technique used for carcinoma of the cervix?

Accepted Answer

New York technique

Answer

Paris technique

Answer

Manchester technique

Answer

Stockholm technique

Question 7

What grade of mucositis is characterized by large painful ulcers?

Accepted Answer

Grade 3

Answer

Grade 1

Answer

Grade 2

Answer

Grade 4

Question 8

What is the best investigation for planning radiotherapy for carcinoma of the esophagus?

Accepted Answer

PET scan

Answer

CT scan

Answer

Ultrasound

Answer

MRI

Question 9

Which of the following is used in External Beam Radiotherapy?

Accepted Answer

LINAC

Answer

I-131

Answer

P-32

Answer

I-125

Question 10

Whole body radiation is indicated in which of the following conditions?

Accepted Answer

Bone marrow transplantation

Answer

Advanced head & neck tumours

Answer

Medulloblastoma

Answer

Mycosis fungoides

Radiation Oncology Basics — MCQs

Radiation Oncology Basics — MCQs

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