A 80-year-old male patient recently diagnosed with non-Hodgkin’s lymphoma was staed on treatment with R- CHOP chemotherapy regimen. After few days, the patient comes to the clinic with complaints of tingling in his hands and feet. Neurological examination shows symmetric “stocking and glove” type distal neuropathy. If the patient’s symptoms are believed to be due to chemotherapy regimen, the drug responsible for these symptoms causes cell cycle arrest during which of the following stages?

**Core Concept**
The question requires knowledge of the mechanism of action of chemotherapy agents, specifically those used in the R-CHOP regimen, and their potential side effects. The correct answer involves understanding the cell cycle and how certain chemotherapy agents cause cell cycle arrest.

**Why the Correct Answer is Right**
The R-CHOP regimen consists of Rituximab, Cyclophosphamide, Hydroxydaunorubicin (Doxorubicin), Oncovin (Vincristine), and Prednisone. The drug responsible for the patient's symptoms is likely Vincristine, a vinca alkaloid that binds to tubulin and prevents microtubule formation. This leads to cell cycle arrest at the G2/M phase of the cell cycle, disrupting mitosis and causing neurotoxicity. The "stocking and glove" type distal neuropathy is a classic symptom of chemotherapy-induced peripheral neuropathy, which is a well-known side effect of Vincristine.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable, as this is a blank space.
* **Option B:** This option is not relevant to the context of the question.
* **Option C:** This option is not correct because the cell cycle arrest caused by Vincristine occurs at the G2/M phase, not the G1 phase.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Vincristine is a neurotoxic agent that can cause peripheral neuropathy, and its use should be carefully monitored in patients with a history of neurological disorders.

**Correct Answer:** C. G2/M

✓ Correct Answer: D. M phase