Principles of Radiation Therapy — MCQs
Which of the following statements about thyroid eye disease is false?
What is the most effective management strategy for osteoradionecrosis?
A radioisotope used in both teletherapy and brachytherapy is
Principles used in Radio Therapy are:
Treatment of resectable T4N0M0 stage of head and neck carcinoma is?
Which of the following is not a cause of oropharyngeal carcinoma?
Epithelioid hemangioendothelioma of the nose is classified as which of the following?
What is the commonest malignancy type in the oral cavity?
Recurrent or residual cancer of the nasopharynx after supervoltage radiotherapy is treated by which of the following?
A 13-year-old boy presents with cheek swelling and recurrent epistaxis. What is the most likely cause?
Principles of Radiation Therapy Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following statements about thyroid eye disease is false?
- A. NOSPECS score is used to classify thyroid eye disease
- B. The management corresponds to improvement in thyrotoxic state (Correct Answer)
- C. Can lead to visual loss
- D. Seen in more than 10% of patients with hyperthyroidism
Explanation: ***The management corresponds to improvement in thyrotoxic state*** - Thyroid eye disease (TED) is an **autoimmune condition** that runs independently of the thyroid's hormonal status [1]. While hyperthyroidism can trigger or worsen TED, treating the hyperthyroidism does not necessarily resolve or improve the eye symptoms [2]. - The disease course of TED is often **biphasic**, with an active inflammatory phase followed by a quiescent phase. Treatment decisions for TED are based on the severity and activity of the eye disease itself, not solely on the thyroid hormone levels. *NOSPECS score is used to classify thyroid eye disease* - The **NOSPECS classification system** is a well-established method for grading the severity of thyroid eye disease. - This acronym stands for **N**o signs or symptoms, **O**nly signs (e.g., lid retraction) no symptoms, **S**oft tissue involvement, **P**roptosis, **E**xtraocular muscle involvement, **C**orneal involvement, and **S**ight loss (optic neuropathy). *Can lead to visual loss* - Thyroid eye disease can cause **optic nerve compression** due to enlarged extraocular muscles or increased orbital fat, leading to **compressive optic neuropathy** and potentially irreversible visual loss. - Severe **corneal exposure** from proptosis and lid retraction can also lead to corneal ulceration, infection, and scaring, affecting vision. *Seen in more than 10% of patients with hyperthyroidism* - Thyroid eye disease is the **most common extrathyroidal manifestation** of Graves' disease, occurring in approximately 25-50% of patients with Graves' hyperthyroidism [1]. - While it is less common in other forms of hyperthyroidism or euthyroid individuals, the prevalence in Graves' disease alone is significantly higher than 10%.
Question 2: What is the most effective management strategy for osteoradionecrosis?
- A. Hyperbaric oxygen therapy
- B. Fluoride treatment
- C. Combination of hyperbaric oxygen therapy and surgical removal of necrotic bone (Correct Answer)
- D. Surgical removal of necrotic bone
Explanation: ***Combination of hyperbaric oxygen therapy and surgical removal of necrotic bone*** - This combined approach is the most effective strategy for **osteoradionecrosis** as it addresses both the underlying tissue damage and the removal of compromised bone. - **Hyperbaric oxygen therapy** promotes angiogenesis and increases oxygenation in damaged tissues, while **surgical debridement** removes non-viable bone to facilitate healing. *Hyperbaric oxygen therapy* - While beneficial for promoting tissue healing and angiogenesis, **hyperbaric oxygen therapy alone** may not be sufficient to resolve established osteoradionecrosis, particularly in cases with significant bone sequestration. - It works by increasing the **partial pressure of oxygen** in tissues, which can improve blood supply and support cellular repair, but often needs debridement of necrotic tissue to be fully effective. *Fluoride treatment* - **Fluoride treatment** is primarily used to prevent dental caries and manage **dentin hypersensitivity**, not to treat established osteoradionecrosis. - It has no direct therapeutic role in revascularizing necrotic bone or promoting the healing of radiation-damaged tissue. *Surgical removal of necrotic bone* - **Surgical debridement** is crucial for removing non-viable bone tissue, which acts as a barrier to healing and can harbor infection. - However, without adjunctive therapies like **hyperbaric oxygen**, simple debridement may not adequately address the underlying **hypoxia and hypovascularity** of the irradiated tissue, leading to persistent or recurrent necrosis.
Question 3: A radioisotope used in both teletherapy and brachytherapy is
- A. Gold-198
- B. Iodine-125
- C. Cesium-137 (Correct Answer)
- D. Radium-226
Explanation: ***Cesium-137*** - Cesium-137 is used in both **teletherapy (external beam radiation)** units, particularly older ones, and in **brachytherapy sources** for interstitial or intracavitary applications. - It emits **gamma rays** with an energy suitable for both types of therapy, giving it versatility. *Gold-198* - **Gold-198** is primarily used in **brachytherapy** as temporary or permanent implants, particularly for conditions like prostate cancer. - Its short half-life and primary emission of **beta particles** with accompanying gamma rays make it less suitable for external teletherapy applications. *Iodine-125* - **Iodine-125** is almost exclusively used in **low-dose-rate (LDR) brachytherapy**, commonly for prostate cancer and ocular melanomas. - It emits **low-energy gamma and X-rays**, which have a very limited range, making it unsuitable for teletherapy. *Radium-226* - **Radium-226** was historically one of the first radioisotopes used in brachytherapy but has largely been replaced due to its strong **gamma emissions** and the associated safety risks. - It was never widely adopted for teletherapy machines because its decay products include gaseous **radon**, posing significant handling and safety challenges.
Question 4: Principles used in Radio Therapy are:
- A. Ultrasonic effect
- B. Charring of nucleoprotein
- C. Infrared rays
- D. Ionizing radiation (Correct Answer)
Explanation: ***Ionizing radiation*** - Radiation therapy primarily utilizes **ionizing radiation** (e.g., X-rays, gamma rays, protons) to damage the **DNA** of cancer cells. - This damage prevents cancer cells from growing and dividing, leading to their death and tumor shrinkage. *Ultrasonic effect* - **Ultrasound** uses high-frequency sound waves for imaging (sonography) and, in some therapeutic applications, to generate heat or mechanically disrupt tissues. - It is not the primary principle for general **radiotherapy** which aims to destroy cancer cells via DNA damage. *Charring of nucleoprotein* - **Charring** refers to the severe burning of organic material, often resulting in carbonization. - While radiation can cause significant cellular damage, the primary mechanism is not macroscopic charring but rather precise **DNA damage** at a molecular level. *Infrared rays* - **Infrared rays** are a form of electromagnetic radiation associated with heat, used in some warming therapies or for imaging (thermography). - They lack the energy to cause **ionization** and significant DNA damage to effectively treat cancer in the manner of therapeutic radiation.
Question 5: Treatment of resectable T4N0M0 stage of head and neck carcinoma is?
- A. Radiotherapy alone
- B. Surgery and Radiotherapy (Correct Answer)
- C. Chemoradiation
- D. Surgery alone
Explanation: ***Surgery and Radiotherapy*** - For **resectable T4N0M0 head and neck carcinoma**, the standard treatment is **surgical resection** of the primary tumor followed by **adjuvant radiotherapy**. - This approach achieves optimal **local control** for advanced primary tumors without nodal involvement. - **Adjuvant radiotherapy** is essential for T4 tumors due to high risk of microscopic residual disease and local recurrence. - Surgery allows for complete tumor removal with negative margins, while radiotherapy addresses subclinical disease. *Radiotherapy alone* - Radiotherapy alone is **insufficient as monotherapy** for T4 tumors due to the large tumor burden and extensive local invasion. - Single modality radiation cannot reliably achieve adequate tumor control for advanced primary lesions. - Generally reserved for early-stage disease or patients unfit for surgery. *Chemoradiation* - **Definitive chemoradiation** is an alternative for **unresectable T4 tumors** or when organ preservation is desired (e.g., laryngeal cancer). - For **resectable** T4N0M0 disease, surgery with adjuvant RT is preferred as it provides better local control and allows pathological staging. - Chemoradiation may be used postoperatively if high-risk features are found (positive margins, perineural invasion, extranodal extension). - In this **N0 case with resectable tumor**, upfront surgery is the preferred initial approach. *Surgery alone* - While surgical resection is crucial for T4 tumors, **surgery alone is inadequate** due to high risk of locoregional recurrence. - T4 classification indicates extensive local invasion, necessitating **adjuvant radiotherapy** to eradicate microscopic disease. - Combined modality treatment (surgery + RT) significantly improves local control and survival compared to surgery alone.
Question 6: Which of the following is not a cause of oropharyngeal carcinoma?
- A. Occupational exposure to hydrochloric acid (Correct Answer)
- B. Smoking
- C. Human Papilloma Virus infection
- D. Occupational exposure to isopropyl oil
Explanation: **Explanation:** The primary risk factors for oropharyngeal carcinoma (OPC) are lifestyle-related and viral, rather than chemical or industrial. **1. Why Option A is the Correct Answer:** Occupational exposure to **hydrochloric acid (HCl)** is primarily associated with dental erosion and irritation of the upper respiratory tract, but it is **not** a recognized carcinogen for the oropharynx. In contrast, exposure to strong inorganic acid mists (like sulfuric acid) is linked specifically to **laryngeal cancer**, not oropharyngeal cancer. **2. Analysis of Other Options:** * **Smoking (Option B):** Tobacco use is a classic risk factor. Carcinogens like nitrosamines and polycyclic aromatic hydrocarbons cause field cancerization, leading to squamous cell carcinoma (SCC) of the entire aerodigestive tract. * **Human Papilloma Virus (Option C):** HPV (specifically **Type 16**) is now the leading cause of oropharyngeal cancer globally, especially involving the palatine tonsils and base of tongue. HPV-positive tumors have a better prognosis than tobacco-related ones. * **Isopropyl Oil (Option D):** Occupational exposure to the manufacture of isopropyl alcohol (specifically the "strong acid process" involving isopropyl oil) is a documented risk factor for cancers of the **paranasal sinuses and the oropharynx**. **Clinical Pearls for NEET-PG:** * **Most Common Site:** The **palatine tonsil** is the most common site for oropharyngeal SCC. * **HPV Marker:** **p16** immunohistochemistry is used as a surrogate marker for HPV-associated oropharyngeal cancer. * **Plummer-Vinson Syndrome:** Associated with post-cricoid (hypopharyngeal) carcinoma, not primarily oropharyngeal. * **Diet:** Deficiencies in Vitamin A and C are also implicated in the development of oral and pharyngeal malignancies.
Question 7: Epithelioid hemangioendothelioma of the nose is classified as which of the following?
- A. Carcinoma
- B. Sarcoma (Correct Answer)
- C. Carcinosarcoma
- D. Hamartoma
Explanation: **Explanation:** **Epithelioid Hemangioendothelioma (EHE)** is a rare vascular neoplasm of intermediate malignancy. The correct classification is **Sarcoma** because it originates from mesenchymal tissue (specifically vascular endothelial cells). 1. **Why Sarcoma is Correct:** By definition, a sarcoma is a malignant tumor arising from mesenchymal cells (bone, cartilage, fat, muscle, or blood vessels). EHE is characterized by "epithelioid" endothelial cells that mimic epithelial cells in appearance but are positive for vascular markers like **CD31, CD34, and Factor VIII-related antigen**. It is considered an intermediate-grade vascular sarcoma, falling between a benign hemangioma and a highly aggressive angiosarcoma. 2. **Why Other Options are Incorrect:** * **Carcinoma:** These are malignant tumors of **epithelial** origin (e.g., Squamous Cell Carcinoma). While EHE has "epithelioid" features histologically, its lineage is endothelial (mesenchymal). * **Carcinosarcoma:** This is a true "mixed" tumor containing both malignant epithelial and malignant mesenchymal components. * **Hamartoma:** This is a benign, disorganized growth of mature native tissue. EHE is a neoplastic process with metastatic potential, not a developmental malformation. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for "intracytoplasmic vacuoles" (lumina) containing red blood cells within epithelioid cells. * **Genetics:** Often associated with a specific translocation: **t(1;3)(p36;q25)** resulting in the **WWTR1-CAMTA1** fusion gene. * **Behavior:** It is locally invasive and has a metastatic rate of approximately 20-30%. * **Treatment:** Wide surgical excision is the primary modality; it is generally resistant to radiotherapy and chemotherapy.
Question 8: What is the commonest malignancy type in the oral cavity?
- A. Adenocarcinoma
- B. Transitional cell carcinoma
- C. Squamous cell carcinoma (Correct Answer)
- D. Basal cell carcinoma
Explanation: **Explanation:** **Correct Answer: C. Squamous cell carcinoma (SCC)** The oral cavity is lined by **stratified squamous epithelium**. Malignant transformation of these cells leads to Squamous Cell Carcinoma, which accounts for over **90-95%** of all oral cavity cancers. The primary risk factors include tobacco (smoking and smokeless), betel nut chewing, and chronic alcohol consumption. The most common site within the oral cavity for SCC is the **lower lip** (globally) or the **buccal mucosa/retro-molar trigone** (in the Indian subcontinent due to tobacco chewing habits). **Why other options are incorrect:** * **A. Adenocarcinoma:** These arise from glandular tissue. In the oral cavity, they originate from minor salivary glands. While they are the second most common group, they are far less frequent than SCC. * **B. Transitional cell carcinoma:** This type of epithelium is characteristic of the urinary tract (urothelium). It is not found in the oral cavity. * **D. Basal cell carcinoma (BCC):** BCC is a skin cancer (rodent ulcer) arising from the basal layer of the epidermis. While it commonly occurs on the face (above the line joining the tragus to the angle of the mouth), it does not arise from the oral mucosa. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site (India):** Buccal mucosa (often referred to as the "Indian Oral Cancer"). * **Most common site (Global):** Lower lip. * **Premalignant conditions:** Leukoplakia (most common), Erythroplakia (highest risk of transformation), and Oral Submucous Fibrosis (OSMF). * **Lymphatic spread:** Usually to Level I, II, and III neck nodes. * **Staging:** The "Worst Pattern of Invasion" (WPOI) and "Depth of Invasion" (DOI) are critical prognostic factors in the latest AJCC staging.
Question 9: Recurrent or residual cancer of the nasopharynx after supervoltage radiotherapy is treated by which of the following?
- A. Intracavitary radioactive implants
- B. Cryotherapy
- C. Surgery
- D. All of the above (Correct Answer)
Explanation: **Explanation:** The primary treatment for Nasopharyngeal Carcinoma (NPC) is **Radiotherapy (RT)** because the tumor is highly radiosensitive and the anatomical location makes primary surgical access difficult. However, managing **recurrent or residual disease** after full-course supervoltage radiotherapy is challenging because the area has already received its maximum tolerance dose of radiation. **Why "All of the above" is correct:** When external beam radiation fails, a multi-modal salvage approach is required: 1. **Intracavitary Radioactive Implants (Brachytherapy):** This allows for a high dose of radiation to be delivered directly to the tumor site while sparing the surrounding healthy tissues that were previously irradiated. Gold grains or Iridium-192 are commonly used. 2. **Surgery (Nasopharyngectomy):** While technically demanding, salvage surgery (via maxillary swing or endoscopic approaches) is indicated for localized resectable recurrences. 3. **Cryotherapy:** This is a palliative or adjunct option used to destroy localized residual tumor cells using extreme cold, especially in patients who are not candidates for major surgery. **Clinical Pearls for NEET-PG:** * **Primary Treatment of Choice:** Radiotherapy (specifically IMRT) is the gold standard for NPC. * **EBV Association:** NPC (especially Type 2 and 3) is strongly associated with the **Epstein-Barr Virus**. Monitoring EBV DNA levels is useful for detecting recurrence. * **Fossa of Rosenmüller:** This is the most common site of origin for NPC. * **Trotter’s Triad:** A classic presentation of NPC involving: 1. Conductive deafness (Eustachian tube blockage) 2. Ipsilateral temporoparietal neuralgia (CN V involvement) 3. Palatal paralysis (CN X involvement)
Question 10: A 13-year-old boy presents with cheek swelling and recurrent epistaxis. What is the most likely cause?
- A. Angiofibroma (Correct Answer)
- B. Carcinoma of the nasopharynx
- C. Rhabdomyosarcoma
- D. None of the above
Explanation: **Explanation:** The clinical presentation of a **13-year-old boy** with **recurrent epistaxis** and **cheek swelling** is a classic "spotter" for **Juvenile Nasopharyngeal Angiofibroma (JNA)**. **1. Why Angiofibroma is correct:** JNA is a benign but locally aggressive, highly vascular tumor that occurs almost exclusively in **adolescent males** (testosterone-dependent). * **Epistaxis:** The most common symptom is profuse, painless, recurrent epistaxis due to the tumor's extreme vascularity. * **Cheek Swelling:** As the tumor grows, it typically expands from the sphenopalatine foramen into the **pterygopalatine fossa** and then laterally into the **infratemporal fossa**, leading to the characteristic "frog-face" deformity or cheek swelling. **2. Why other options are incorrect:** * **Carcinoma of the nasopharynx:** While it can cause epistaxis and nasal obstruction, it is rare in young children and more commonly presents with cervical lymphadenopathy and serous otitis media. * **Rhabdomyosarcoma:** This is the most common soft tissue sarcoma in children. While it can occur in the head and neck, it usually presents as a rapidly enlarging, painful mass rather than the classic pattern of recurrent, profuse epistaxis seen in JNA. **3. High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Sphenopalatine foramen (near the posterior end of the middle turbinate). * **Holman-Miller Sign (Antral Sign):** Anterior bowing of the posterior wall of the maxillary sinus seen on CT/MRI. * **Diagnosis:** Contrast-enhanced CT (CECT) is the investigation of choice. **Biopsy is strictly contraindicated** due to the risk of torrential hemorrhage. * **Treatment:** Surgical excision (Pre-operative embolization is often done to reduce blood loss).
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