What is the role of Otoacoustic Emissions (OAE) in adjusting cisplatin dose?

Role of Otoacoustic Emissions (OAE) in Cisplatin Dose Adjustment

Otoacoustic emissions (OAE) testing should be used for early detection of cisplatin-induced ototoxicity and to guide dose adjustments when hearing loss reaches Chang grade 2a or higher, as this correlates with clinically significant hearing impairment requiring intervention. 1

Advantages of OAE Testing for Ototoxicity Monitoring

OAE testing offers several advantages over conventional audiometry for monitoring cisplatin-induced ototoxicity:

• More sensitive to early cochlear damage than pure-tone audiometry 2, 3
• Can detect changes in outer hair cell function before hearing loss becomes apparent on audiograms 2
• Particularly valuable for patients who may not be able to cooperate with behavioral hearing tests during chemotherapy 4
• Can detect damage at frequencies above 3 kHz without corresponding changes in pure-tone audiometry 3

Types of OAE Testing for Ototoxicity Monitoring

Two main types of OAE testing are used for cisplatin ototoxicity monitoring:

1. Distortion Product OAE (DPOAE):

   • Most sensitive method for early detection of cisplatin ototoxicity 3
   • Can test higher frequencies where damage first occurs
   • Provides quantifiable metrics that can be tracked over time
   • Superior to transient evoked OAE for ototoxicity monitoring 3

2. Transient Evoked OAE (TEOAE):

   • Shows decreased emission levels and reproducibility at high frequencies (4 kHz) 3
   • Less sensitive than DPOAE but still more sensitive than conventional audiometry 2

Protocol for OAE Monitoring and Dose Adjustment

Baseline Assessment

• Perform baseline OAE testing before initiating cisplatin therapy 5
• Focus on high frequencies (≥4 kHz) as these are affected first 1
• Document pre-treatment hearing status as baseline hearing is a significant factor in risk assessment 6, 4

Monitoring Schedule

• Perform OAE testing before each cisplatin dose 5
• Continue monitoring for delayed-onset hearing loss with follow-up OAEs at 3,6, and 12 months post-treatment 1

Interpretation and Dose Adjustment Criteria

When interpreting OAE results for dose adjustment decisions:

1. Early Warning Signs (Continue with planned dose but increase monitoring frequency):

   • Decrease in DPOAE amplitude at frequencies ≥3 kHz 3
   • Reduction in TEOAE emission level >13% from baseline 2

2. Dose Modification Threshold (Consider dose reduction of 25-50%):

   • When hearing loss reaches Chang grade 2a or higher 1
   • Significant threshold shift in DPOAE with reduced dynamic range 3
   • Complete disappearance of OAE responses at specific frequencies

3. Severe Ototoxicity (Consider 50% dose reduction or alternative therapy):

   • Chang grade 3 hearing loss 1
   • Absence of OAE responses across multiple frequencies
   • Symptoms of tinnitus or subjective hearing loss with corresponding OAE changes

Risk Factors to Consider with OAE Monitoring

When interpreting OAE changes, consider these risk factors that increase ototoxicity risk:

• Young age (<5 years) 5
• Cumulative cisplatin dose (higher risk with increasing dose) 6, 4
• Baseline hearing status (better pre-treatment hearing paradoxically increases risk) 4
• Concurrent use of other ototoxic medications (aminoglycosides, vancomycin) 5
• Renal impairment 5
• Prior or concurrent cranial radiation 5

Practical Implementation

1. Use DPOAE as the primary OAE monitoring method, focusing on frequencies near each patient's high-frequency DPOAE limit 6

2. Combine OAE metrics with pre-treatment hearing status and cumulative cisplatin dose for the most accurate ototoxicity risk assessment 6, 4

3. When significant OAE changes are detected that correspond to Chang grade 2a or higher hearing loss, implement dose adjustments according to the Chang grading system 1

Limitations and Considerations

• OAE testing may not be reliable in patients with pre-existing hearing loss >40 dB
• Environmental noise can affect test results, requiring proper testing conditions
• While OAE changes often precede audiometric changes, some patients may develop audiometric changes without significant OAE changes
• Symptoms of ototoxicity (tinnitus, subjective hearing loss) should not be ignored even if OAE results appear normal 7

By implementing systematic OAE monitoring and following the Chang grading system for dose adjustments, clinicians can minimize permanent hearing damage while maintaining effective cancer treatment.