What is the difference between the ECOG (Eastern Cooperative Oncology Group) and Karnofsky performance status scales in assessing adult cancer patients?

ECOG vs Karnofsky Performance Status Scales

Core Differences

Both ECOG and Karnofsky Performance Status (KPS) scales assess functional status in cancer patients, but they differ fundamentally in scoring direction: ECOG ranges 0-4 where higher scores indicate worse function, while KPS ranges 0-100 where lower scores indicate worse function. 1, 2

Scale Structure

ECOG Performance Status:

• 5-point scale (0-4) 1
• Lower numbers = better function 1
• Simpler, more categorical assessment 3

Karnofsky Performance Status:

• 11-point scale (0-100 in increments of 10) 2, 4
• Higher numbers = better function 1, 2
• Evaluates three core domains: activity level, work capacity, and self-care abilities 2

Standard Conversion Between Scales

The National Comprehensive Cancer Network uses these equivalent cutoffs for treatment decisions: 1

• Good performance status: ECOG 0-2 = KPS ≥60 1, 5
• Poor performance status: ECOG ≥3 = KPS <60 1, 5

More granular empirical conversion (based on 1,385 patient assessments): 6

• ECOG 0 = KPS 100 6
• ECOG 1 = KPS 80-90 6
• ECOG 2 = KPS 60-70 6
• ECOG 3 = KPS 40-50 6
• ECOG 4 = KPS 10-30 6

This conversion achieved 75% accuracy with strong statistical agreement (weighted kappa 0.84). 6

Clinical Treatment Implications

Chemotherapy Eligibility

Patients eligible for systemic therapy (per NCCN guidelines): 1, 5

• ECOG PS ≤2 OR KPS ≥60 1, 5
• Should receive chemotherapy plus best supportive care 1, 5

Patients who should receive best supportive care only: 1, 5

• ECOG PS ≥3 OR KPS <60 1, 5
• No systemic chemotherapy recommended 1, 5

Intensity of Chemotherapy Regimens

Three-drug regimens: 1, 5

• Reserved exclusively for patients with good performance status (KPS ≥80, roughly ECOG 0-1) 1, 5
• Requires access to frequent toxicity monitoring 1, 5

Two-drug regimens: 1, 5

• Preferred for patients with ECOG 2 or lower KPS scores 1, 5
• More appropriate for those with limited monitoring access 1, 5

Comparative Performance in Clinical Practice

Predictive Validity

ECOG demonstrates superior prognostic discrimination compared to KPS. 3 In a prospective study of 536 lung cancer patients with 1,656 performance status assessments, both scales showed strong correlation (Spearman R = -0.869), but multivariate survival analysis revealed ECOG had better ability to discriminate patients with different prognoses. 3

Reliability

Both scales demonstrate high inter-rater reliability when used by trained oncologists: 7

• KPS inter-observer correlation: K = 0.921 7
• ECOG inter-observer correlation: K = 0.914 7
• Intra-observer reliability even higher (K = 0.960-0.993 for KPS; K = 0.920-0.982 for ECOG) 7

Limitations and Biases

Both scales share critical weaknesses that clinicians must recognize: 2, 8

• Subjective assessment: Both are inherently subjective and open to bias 2, 8
• Age bias: Clinicians assign worse scores to patients >65 years despite no objective difference in physical activity 2
• Less predictive in elderly: Both scales are less predictive of cancer outcomes in older adults 2
• Unidimensional: Neither accounts for multimorbidity, frailty, or cognition 8
• Cause-agnostic: Cannot differentiate whether poor performance stems from disease burden, comorbidities, or treatment toxicity—clinically relevant since disease-related poor performance may improve with effective treatment 2

Practical Recommendations

Use ECOG as the primary scale in clinical practice. 3 The simpler 5-point ECOG scale shows better prognostic discrimination and is easier to apply consistently than the 11-point KPS scale. 3

When interpreting published guidelines or trial eligibility: 1, 6

• Apply the standard conversion: ECOG 0-2 = KPS ≥60 for treatment eligibility 1
• Use the granular conversion table for more precise translation between scales 6

Reassess performance status regularly: 5

• Performance status changes over time and should not be recorded only once 8
• If status deteriorates to ECOG ≥3 or KPS <60 during treatment, discontinue chemotherapy and focus on best supportive care 5

Consider supplementing with additional assessment tools: 8

• Clinical Frailty Score for older patients 8
• Palliative Performance Scale (PPS) in palliative care settings, which adds domains for ambulation, self-care, and oral intake 4