A 48-year-old woman with a T3N2M0 squamous cell carcinoma of the floor of mouth is planned for concurrent chemoradiotherapy. She has normal renal function and good performance status. Which chemotherapy regimen is the drug of choice for concurrent administration with radical radiotherapy?

Explanation

## Concurrent Chemoradiotherapy for Locally Advanced Oral Cavity Carcinoma **Key Point:** Weekly cisplatin 40 mg/m² is the gold-standard chemotherapy regimen for concurrent chemoradiotherapy (CCRT) in locally advanced oral cavity carcinoma, as demonstrated by the RTOG and EORTC trials. ### Rationale for Weekly Cisplatin in CCRT **High-Yield:** Weekly cisplatin 40 mg/m² is preferred over other regimens in the concurrent setting because: 1. **Optimal radiosensitization:** Cisplatin enhances radiation-induced DNA damage and overcomes hypoxia-related radioresistance. 2. **Manageable toxicity:** Weekly dosing (rather than high-dose cisplatin every 3 weeks) allows better tolerance when combined with concurrent radiotherapy. 3. **Evidence-based:** RTOG 91-11 and EORTC trials demonstrated superior locoregional control and overall survival with cisplatin-based CCRT. 4. **Renal safety:** Weekly dosing permits adequate hydration between cycles and reduces cumulative nephrotoxicity. ### Comparison of Concurrent Chemotherapy Regimens | Regimen | Dose/Schedule | Setting | Radiosensitization | Toxicity | Evidence | |---------|--------------|---------|-------------------|----------|----------| | **Cisplatin (weekly)** | 40 mg/m² weekly × 6–7 weeks | **CCRT (standard)** | Excellent | Moderate (manageable) | RTOG 91-11, EORTC | | **Cisplatin (high-dose)** | 100 mg/m² every 3 weeks | Induction, then CCRT | Excellent | High (severe) | Not recommended concurrent | | **5-FU + Leucovorin** | 5-FU 1000 mg/m²/day × 4–5 days | Induction only | Poor | Moderate | Inferior to cisplatin in CCRT | | **Docetaxel + Cisplatin** | Docetaxel 20 mg/m² weekly + Cisplatin 20 mg/m² weekly | Experimental CCRT | Excellent but untested | High | Limited data; not standard | | **Cetuximab monotherapy** | 400 mg/m² loading + 250 mg/m² weekly | CCRT (cisplatin-ineligible) | Moderate | Low | BONNER trial; inferior to cisplatin | **Clinical Pearl:** The BONNER trial (2006) compared cetuximab + radiotherapy vs. radiotherapy alone in HNSCC and showed benefit, but cetuximab is reserved for cisplatin-ineligible patients. In a patient with normal renal function, cisplatin is superior. ### Concurrent Chemoradiotherapy Algorithm ```mermaid flowchart TD A[Locally Advanced OCC]:::outcome --> B{Candidate for CCRT?}:::decision B -->|Yes| C{Renal function & performance status?}:::decision C -->|Normal, PS 0-1| D[Weekly Cisplatin 40 mg/m²]:::action C -->|Impaired renal or PS ≥2| E[Cetuximab monotherapy]:::action D --> F[Radical radiotherapy 70 Gy/35 fractions]:::action E --> F F --> G[Reassess at 6-8 weeks]:::decision G -->|Complete response| H[Follow-up surveillance]:::outcome G -->|Partial response| I[Consider salvage surgery]:::action G -->|Progressive disease| J[Palliative care]:::urgent ``` **Mnemonic:** **CCRT-CISPLATIN** = **C**oncurrent **C**hemoradiotherapy **R**equires **T**he **C**hoice of **I**nduction or **S**tandard **P**rotocol: **L**ocal **A**dvanced **T**umors **I**nvolve **N**eeds for cisplatin weekly. **Warning:** High-dose cisplatin (100 mg/m² every 3 weeks) is used for induction chemotherapy, NOT concurrent chemoradiotherapy. Combining high-dose cisplatin with radiotherapy causes severe mucositis, dysphagia, and renal toxicity.