WBR0164
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | |
| Sub Category | |
| Prompt | [[Prompt::A four year old male is brought to the pediatrician by his parents after they noticed a large mass on his left flank and blood in the child’s urine. Biopsy of the mass reveals a mixed population of tubules, small round blue cells and stroma. The child undergoes left nephrectomy and is placed on a course of adjuvant chemotherapy. Two weeks after the chemotherapy is administered, the child complains of dizziness, has trouble walking and displays difficult in dorsiflexing both feet. Which of the following drugs is most likely responsible for these symptoms?]] |
| Answer A | AnswerA::Cisplatin |
| Answer A Explanation | [[AnswerAExp::Incorrect: Cisplatin is a non-cell cycle specific alkylating agent. It inhibits DNA and RNA synthesis by cross-linking DNA strands, thereby causing strand breaks. It is used for genitourinary tumors and is extremely effective for testicular cancers. Its most notable side effects are ototoxicity and nephrotoxicity.]] |
| Answer B | AnswerB::Dactinomyin |
| Answer B Explanation | AnswerBExp::'''Incorrect:''' Dactinomycin inhibits RNA polymerase by intercalating between Cytosine and Guanine nucleotides in DNA. |
| Answer C | AnswerC::Paclitaxel |
| Answer C Explanation | AnswerCExp::'''Incorrect:''' Paclitaxel hyperstabilizes microtubules and inhibits the disassembly of the mitotic spindle, thereby arresting dividing cells in M-phase. It is primarily used in breast and ovarian carcinomas. |
| Answer D | AnswerD::Vinblastine |
| Answer D Explanation | AnswerDExp::'''Incorrect:''' Vinblastine inhibits microtubule assembly but it is not associated with peripheral neuropathy. |
| Answer E | AnswerE::Vincristine |
| Answer E Explanation | [[AnswerEExp::Correct: Vincristine binds to tubulin dimers, thereby inhibiting the assembly of microtubulues and blocking cell progression through mitosis. Vincristine is used in a variety of cancers including Wilms’ tumor, choriocarcinoma and ALL. The most prominent side effect is peripheral neuropathy.]] |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Wilms' tumor or nephroblastoma is a rare cancer of the kidneys that typically occurs in children between the ages of 2 and 4. It may often present with a large flank or abdominal mass, fever and blood in the urine. These tumors are exceptionally responsive to therapy with a 5 year survival of 90%. WIlms’ tumor is most commonly treated with nephrectomy (most tumors are unilateral) followed by one of several possible courses of adjuvant chemotherapy. Nearly all of these regimens include the drug vincristine. Vincristine is a vinca alkaloid that binds to tubulin dimers, thereby inhibiting the assembly of microtubulues and blocking cell progression through mitosis. Vincristine is used in a variety of cancers including Wilms’ tumor, choriocarcinoma and ALL. The most prominent side effect is neurotoxicity which may include arelfexia and peripheral neuropathy. The child in this vignette is exhibiting foot drop, a sign of vincristine induced peripheral neuropathy.
Educational Objective: An important side effect of vincristine therapy is peripheral neuropathy. References: First Aid 2012 page 401 |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Chemotherapy, WBRKeyword::Cancer, WBRKeyword::Kidney, WBRKeyword::Wilms tumor, WBRKeyword::Mitosis, WBRKeyword::Peripheral neuropathy, WBRKeyword::Neuropathy, WBRKeyword::Side effect |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |