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For demonstration of interpreting a strong positive interaction see slides 25-30.

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For demonstration of interpreting a strong positive interaction see slides 25-30.

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    1. For demonstration of interpreting a strong positive interaction see slides 25-30.

    2. NPC-9902 Trial on Therapeutic Gain by Concurrent Chemotherapy and/or Accelerated Fractionation for Locally-Advanced Nasopharyngeal Cancer Anne W. M. Lee for Hong Kong Nasopharyngeal Cancer Study Group

    3. Estimation on Sample & Eligible Patients

    4. NPC-9902: Eligibility Criteria

    5. Eligibility Criteria

    7. RT: Same for all Arms

    8. RT: Fractionation

    9. Treatment in CRT Arm

    10. Statistical Consideration

    11. Other End Points

    12. Participating Centers

    13. Accrual Rate

    15. Results

    16. Patient Characteristics

    17. Tumor Staging

    18. Radiotherapy

    19. Comparison of Prognostic Factors

    20. Major Violation of Protocol

    21. Compliance to Chemotherapy

    22. Acute Toxicity (Grade >3)

    23. Chemotherapy Toxicity in CRT Arm

    24. Overall Acute Toxicity (Grade >3)

    25. Overall Acute Toxicity (Grade >3)

    26. Failure-Free Survival (3-year)

    27. Failure-Free Survival (3-year)

    28. Hazard Ratio = .11 = 1/9 ? Nine-fold decrease in failure with AF + CRT together rather than separately. But the decrease is a product of three effects: RT + AF CRT + CF RT + CF ------------------------------------------------ CRT + AF

    29. That is, the benefit due to CRT + AF being delivered in tandem vs. separately is due to: The apparent disadvantage of CRT + CF over RT + CF (1.1 increase); The apparent disadvantage of RT + AF over RT + CF (1.4 increase); and The advantage of CRT + AF over RT + CF (six-fold reduction): 1.1 ? 1.4 ? 6 = 9, the total interaction effect.

    30. A clinically important question: Suppose we don’t believe the first two effects – we don’t believe that acceleration or adding chemotherapy can cause failures, and fix their hazard ratios at 1.0: What is the significance of the “restricted interaction effect”, the hazard ratio of 6? Answer: p = ????. Modest evidence that AF and CRT do seem to work better together.

    31. Locoregional Failure-Free Rate (3-year)

    32. Distant Failure-Free Rate (3-year)

    33. Disease Status at Last Assessment

    34. Overall Survival

    35. Progression-Free Survival

    36. Late Toxicity (Grade >3)

    37. Late Toxicity (Grade >3)

    38. Subset Analyses – Absolute Gain

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