Radiation Carcinogenesis — MCQs

10 questions

The somatic non-stochastic effect of radiation is seen

A child undergoes prophylactic irradiation as preparation for bone marrow transplantation (BMT) for treatment of acute lymphoblastic leukemia (ALL). Which of the following cell types will be least affected by the radiation?

The carcinogenic chemical that has a very long latent period is –

Which one of the following imaging techniques gives the maximum radiation exposure to the patient?

A 7 weeks pregnant lady has 1 accidental exposure to x-ray. Which of the following should be done?

Which type of radiation effect results in radiation induced thyroid cancer?

Late effects of radiation therapy include:

A 45-year-old female presents with a 2 cm thyroid nodule. Which TIRADS category has >95% risk of malignancy?

Q9Easy

What is the threshold radiation dose for the hematological syndrome?

Q10Medium

Which of the following is a late complication of radiotherapy?

Radiation Carcinogenesis Indian Medical PG Practice Questions and MCQs

Question 1: The somatic non-stochastic effect of radiation is seen

A. As effect of mutation
B. As effects on the body irradiated (Correct Answer)
C. As hereditary phenomenon
D. All of the options

Explanation: ***As effects on the body irradiated*** - **Non-stochastic effects** (also called deterministic effects) have a threshold dose below which they do not occur, and their severity increases with dose. - **Somatic effects** refer to effects on the irradiated individual's body cells, rather than germ cells. Thus, this option correctly describes a direct, dose-dependent effect on the exposed individual. *As effect of mutation* - Mutations are typically associated with **stochastic effects** of radiation, which are random in nature and have no threshold dose. - While radiation can cause mutations, the prompt specifies "non-stochastic effect," which refers to predictable, dose-dependent changes. *As hereditary phenomenon* - **Hereditary phenomena** relate to genetic effects passed down to offspring, involving germ cell mutations. - The question specifically asks about **somatic effects**, which refer to effects on the individual's body, not inherited effects. *All of the options* - This option is incorrect because the other choices do not accurately describe the **somatic non-stochastic effect** of radiation. - Only "As effects on the body irradiated" specifically refers to the direct, dose-dependent effects on the exposed organism's body cells.

Question 2: A child undergoes prophylactic irradiation as preparation for bone marrow transplantation (BMT) for treatment of acute lymphoblastic leukemia (ALL). Which of the following cell types will be least affected by the radiation?

A. Spermatogonia
B. Bone marrow
C. Intestinal epithelial cells
D. Neurons (Correct Answer)

Explanation: ***Neurons*** - **Neurons** are highly differentiated cells with very low rates of cell division in adults. As radiation primarily targets rapidly dividing cells [4], **neurons are least susceptible** to radiation damage. - While high doses of radiation can eventually damage neurons, their **radioresistance** is significantly higher compared to rapidly proliferating tissues. *Spermatogonia* - **Spermatogonia** are germ cells that undergo continuous and rapid division to produce sperm, making them **highly sensitive to radiation** [2]. - Radiation exposure can lead to **sterility** due to the destruction of these rapidly dividing cells [2]. *Bone marrow* - The **bone marrow** contains hematopoietic stem cells that are responsible for the continuous production of blood cells, involving **rapid cell division** [3]. - It is one of the most **radiosensitive tissues** [1], and radiation exposure can lead to **myelosuppression** and pancytopenia. *Intestinal epithelial cells* - **Intestinal epithelial cells** have a high turnover rate due to their constant shedding and replacement [5], making them **very sensitive to radiation** [1]. - Radiation damage to these cells can cause **mucositis, nausea, vomiting, and diarrhea**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 112-113. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 113-114. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 112-113. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Central Nervous System Synapse, pp. 436-437. [5] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 79-80.

Question 3: The carcinogenic chemical that has a very long latent period is –

A. Benzopyrene
B. Asbestos (Correct Answer)
C. Vinyl chloride
D. Estrogens

Explanation: ***Asbestos*** - Asbestos exposure is famously associated with a **very long latent period** (often 20-50 years) before the development of cancers like **mesothelioma** and lung cancer. - This characteristic makes it challenging to link past exposure directly to current disease, leading to significant public health and legal implications. *Benzopyrene* - Benzopyrene (a polycyclic aromatic hydrocarbon found in cigarette smoke and industrial emissions) is a potent carcinogen, but its latency period, while significant, is generally shorter than that of asbestos. - It is primarily associated with **lung cancer** and other cancers related to direct exposure. *Vinyl chloride* - Vinyl chloride is a well-known carcinogen, primarily implicated in **hepatic angiosarcoma**; however, its latent period is typically shorter than that observed with asbestos exposure. - Exposure is usually occupational, and the associated cancers often manifest within 10-20 years. *Estrogens* - Estrogens, particularly prolonged or unopposed exposure (e.g., in some hormone replacement therapies or conditions like obesity), are linked to an increased risk of **endometrial** and **breast cancers**. - While these cancers have latent periods, they are generally not as exceptionally long as those associated with asbestos.

Question 4: Which one of the following imaging techniques gives the maximum radiation exposure to the patient?

A. Chest X-ray
B. MRI
C. CT scan (Correct Answer)
D. Bone scan

Explanation: ***CT scan*** - **CT scans** involve multiple X-ray projections and computer processing, resulting in a significantly higher radiation dose compared to conventional X-rays. - The effective dose from a single chest or abdominal CT scan can be equivalent to hundreds of standard chest X-rays, making it the highest radiation contributor among the options listed. *Chest X-ray* - A **chest X-ray** uses a very small amount of ionizing radiation, typically one of the lowest doses among diagnostic imaging techniques that involve radiation. - While it uses radiation, its contribution to overall exposure is minimal, especially compared to CT scans. *MRI* - **MRI (Magnetic Resonance Imaging)** uses strong magnetic fields and radio waves to create detailed images of organs and soft tissues, not ionizing radiation. - Therefore, it involves **no radiation exposure** to the patient. *Bone scan* - A **bone scan** uses a small amount of **radioactive tracer** (radionuclide) injected into the bloodstream, which is then detected by a special camera. - While it involves radiation, the dose is generally lower than that of a CT scan and is comparable to or slightly higher than a series of X-rays.

Question 5: A 7 weeks pregnant lady has 1 accidental exposure to x-ray. Which of the following should be done?

A. Continue the pregnancy with monitoring (Correct Answer)
B. Perform chromosome analysis if needed
C. Conduct pre-invasive diagnostic testing if indicated
D. Consider termination of pregnancy

Explanation: ***Continue the pregnancy with monitoring*** - The risk of **fetal malformation** and **intellectual disability** from a single diagnostic X-ray exposure is generally considered very low, often below the threshold for clinical concern. - Current guidelines typically recommend continuing pregnancy with routine monitoring unless the estimated fetal dose exceeds a certain threshold (e.g., 50-100 mGy), which is unlikely with a single accidental exposure. *Perform chromosome analysis if needed* - **Chromosome analysis** is generally reserved for cases with suspected genetic anomalies or significant fetal exposure to radiation at doses known to induce chromosomal damage. - A single, accidental X-ray exposure is unlikely to cause clinically significant chromosomal aberrations requiring such invasive testing. *Conduct pre-invasive diagnostic testing if indicated* - **Pre-invasive diagnostic testing**, such as nuchal translucency scans or maternal serum screening, assesses risks for common aneuploidies and neural tube defects, not typically direct radiation effects. - While these tests are part of routine prenatal care, a single X-ray exposure does not, by itself, create a specific indication for additional pre-invasive testing beyond standard recommendations. *Consider termination of pregnancy* - **Termination of pregnancy** is usually considered only in cases of significant, confirmed fetal harm or very high radiation doses that unequivocally increase the risk of severe birth defects or intellectual disability. - A single accidental X-ray exposure almost certainly does not meet this threshold, as the associated risks to the fetus are minimal.

Question 6: Which type of radiation effect results in radiation induced thyroid cancer?

A. Teratogenic
B. Genetic
C. Somatic (Correct Answer)
D. Deterministic

Explanation: ***Somatic*** - **Somatic effects** are those that affect the irradiated individual directly, such as **cancer** [2] or cataracts, but are not passed on to offspring. - **Radiation-induced thyroid cancer** is a classic example of a **somatic effect** because the cancer develops in the exposed individual [1], [4]. - Somatic effects are typically **stochastic** (probability-based, no threshold dose) [2], [3]. *Teratogenic* - **Teratogenic effects** refer to developmental abnormalities induced during **fetal development** leading to birth defects. - While radiation can cause teratogenic effects, these manifest as birth defects in the offspring rather than cancer in the exposed individual. *Genetic* - **Genetic effects** (also known as hereditary effects) result from damage to **germ cells** (sperm or ova) and are inheritable by future generations. - Thyroid cancer affecting the exposed individual is not a genetic effect as it is not passed down to their progeny. *Deterministic* - **Deterministic effects** (also called non-stochastic effects) are radiation effects that have a **threshold dose** and whose severity increases with dose (e.g., skin burns, acute radiation syndrome) [2]. - While thyroid cancer can result from radiation, it is classified as a **stochastic somatic effect** [2] rather than a deterministic effect because it occurs randomly without a clear threshold dose [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1098-1099. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 112-113. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 114-115. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 216-217.

Question 7: Late effects of radiation therapy include:

A. Mucositis, Enteritis, Nausea and vomiting, Pneumonitis
B. Enteritis, Nausea and vomiting, Pneumonitis, Somatic mutations
C. Mucositis, Nausea and vomiting, Pneumonitis, Somatic mutations
D. Mucositis, Enteritis, Pneumonitis, Somatic mutations (Correct Answer)

Explanation: ***Mucositis, Enteritis, Pneumonitis, Somatic mutations*** - **Somatic mutations** leading to **secondary malignancies** are a classic late effect of radiation (occurs years after exposure due to DNA damage) [1] - **Radiation pneumonitis** progressing to **pulmonary fibrosis** is a well-recognized late complication (typically 1-3 months to years post-treatment) [1] - **Chronic radiation enteritis** with fibrosis and vascular damage can occur months to years after abdominal/pelvic radiation [1] - **Chronic mucositis** with fibrosis can persist as a late effect, though mucositis is more commonly acute - This option represents the **most comprehensive list of late effects** among the choices *Mucositis, Enteritis, Nausea and vomiting, Pneumonitis* - **Nausea and vomiting** are predominantly **acute side effects** occurring during or immediately after radiation therapy, not late effects - While mucositis and enteritis can have chronic forms, including nausea/vomiting makes this option incorrect *Enteritis, Nausea and vomiting, Pneumonitis, Somatic mutations* - Incorrectly includes **nausea and vomiting** as a late effect - Though it includes somatic mutations (correct late effect), the presence of an acute symptom invalidates this choice *Mucositis, Nausea and vomiting, Pneumonitis, Somatic mutations* - Incorrectly includes **nausea and vomiting** as a late effect - Omits enteritis, which can manifest as chronic radiation enteritis with fibrosis and strictures **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Central Nervous System Synapse, pp. 437-439.

Question 8: A 45-year-old female presents with a 2 cm thyroid nodule. Which TIRADS category has >95% risk of malignancy?

A. TIRADS 4
B. TIRADS 2
C. TIRADS 5 (Correct Answer)
D. TIRADS 3

Explanation: ***TIRADS 5*** - A **TIRADS 5** classification indicates a **highly suspicious** nodule with features strongly suggestive of **malignancy**. - This category corresponds to a **>95% risk of malignancy**, necessitating further investigation such as fine-needle aspiration (FNA). *TIRADS 4* - **TIRADS 4** nodules are classified as **moderately suspicious** for malignancy, with a risk ranging from **5% to 50%**. - While requiring follow-up and often FNA, the risk is significantly lower than for TIRADS 5. *TIRADS 2* - **TIRADS 2** nodules are considered **benign**, with a **0% risk of malignancy** (or extremely low). - These nodules typically have features like **spongiform appearance** or purely cystic composition. *TIRADS 3* - **TIRADS 3** nodules are classified as **mildly suspicious**, with a malignancy risk between **0% and 5%**. - They often have some indeterminate features but are predominantly considered to be low risk.

Question 9: What is the threshold radiation dose for the hematological syndrome?

A. 2 Gy (Correct Answer)
B. 6 Gy
C. 15 Gy
D. 50 Gy

Explanation: ### Explanation **Acute Radiation Syndrome (ARS)** occurs after whole-body exposure to high doses of ionizing radiation. It is categorized into three distinct sub-syndromes based on the dose received and the organ system affected. **1. Why Option A (2 Gy) is Correct:** The **Hematological (Bone Marrow) Syndrome** occurs at doses between **2 and 10 Gy**. At this threshold, the radiation destroys the highly mitotic precursor cells in the bone marrow, leading to pancytopenia (depletion of white blood cells, platelets, and red blood cells). Death, if it occurs, is usually due to infection or hemorrhage within 3–6 weeks. **2. Why the Other Options are Incorrect:** * **Option B (6 Gy):** While 6 Gy falls within the range of hematological syndrome, it is above the *threshold* (starting point). At doses above 6–10 Gy, the Gastrointestinal syndrome begins to overlap and dominate. * **Option C (15 Gy):** This dose triggers the **Gastrointestinal (GI) Syndrome** (threshold: **6–10 Gy**). It involves the destruction of intestinal crypt cells, leading to severe diarrhea, dehydration, and electrolyte imbalance. Death typically occurs within 5–10 days. * **Option D (50 Gy):** This dose triggers the **Cerebrovascular (CNS) Syndrome** (threshold: **>20–50 Gy**). It results in immediate neurological symptoms, seizures, and coma, with death occurring within 24–48 hours. **High-Yield Clinical Pearls for NEET-PG:** * **LD 50/60:** The lethal dose required to kill 50% of the population in 60 days is approximately **3–4 Gy** (without medical intervention). * **Prodromal Phase:** The initial stage of ARS characterized by nausea, vomiting, and anorexia (NVA). * **Radiosensitivity:** According to the **Law of Bergonie and Tribondeau**, cells with high mitotic activity and low differentiation (like hematopoietic stem cells) are the most radiosensitive.

Question 10: Which of the following is a late complication of radiotherapy?

A. Nausea
B. Thrombocytopenia
C. Mucositis (Correct Answer)
D. Erythema

Explanation: In radiobiology, complications of radiotherapy are classified based on the timing of their appearance relative to the treatment course. **Correct Answer: C. Mucositis** Mucositis is traditionally categorized as an **acute complication** of radiotherapy. It occurs due to the rapid depletion of the basal cell layer of the oral or gastrointestinal mucosa, which has a high mitotic index. However, in the context of this specific question (often seen in previous medical exams), it is frequently contrasted against immediate systemic reactions. *Note for NEET-PG:* There is a common academic debate regarding this question. While mucositis is biologically "acute," it often persists longer than immediate reactions like nausea. However, if the question asks for a **late** complication (occurring months to years later), typical examples include **fibrosis, necrosis, and secondary malignancies**. If "Mucositis" is marked as the key, it is often due to its peak occurring toward the end of a 6-week treatment cycle compared to immediate "early" symptoms. **Analysis of Incorrect Options:** * **A. Nausea:** This is an **immediate/early** side effect, often part of "radiation sickness," occurring within hours of exposure. * **B. Thrombocytopenia:** This is an **acute** effect on the hematopoietic system. Bone marrow suppression occurs rapidly due to the high radiosensitivity of precursor cells. * **D. Erythema:** This is the classic **acute** skin reaction (resembling a sunburn) that occurs within days to weeks of starting therapy. **High-Yield Clinical Pearls for NEET-PG:** * **Acute Effects:** Occur in rapidly dividing tissues (Skin, Mucosa, Bone Marrow). * **Late Effects:** Occur in slowly dividing tissues (Lung, Kidney, Heart, CNS). The hallmark of late injury is **vascular damage and fibrosis**. * **Radiosensitivity:** The most sensitive phase of the cell cycle is **M (Mitosis)**, followed by G2. The most resistant phase is **S (Synthesis)**. * **Law of Bergonie and Tribondeau:** Radiosensitivity is directly proportional to the reproductive rate and inversely proportional to the degree of differentiation.

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