# Presentation: 712852

## Diagnostic Assays to Plan Specific Drug Treatment 

- Elizabeth Hammond MD

## Criteria for Development of Diagnostic assays

- Defined assay characteristics for total test
- Standardized procedures for assay, reference materials and training plan to assure  initial and ongoing competence
- Acceptable interlaboratory variability evaluated in standard manner, possibly using TMA’s
- Plan for new laboratory validation
- Plan for ongoing laboratory competence assessment

## Assay Characteristics

- Specimen adequacy: definition of unacceptable samples
- Specimen handling: time from surgery to processing, time in fixative, temperature
- Standardized Reference Materials
- Assay conditions: precise, clearly reported
- Interpretation and reporting criteria: precise, including how reference material is used in the evaluation and acceptable limits of interobserver variation

## CAP FISH Survey Results

**FISH amplified**
- 2000: 35 participants
- 35/35 = amplified
- 2001: 63 participants
- 58/63= amplified
- (others= no response)

**FISH non amplified**
- 2000: 35 participants
- 35/35= non amplified
- 2001: 63 participants
- 49/63= non amplified
- (others= no response)

- CAP CYH survey results, 2000-2001

## CAP IHC (MK) Survey 

- FISH amplified case
- 357  participants
- IHC scores:
- 0        19 (3.7%)
- 1+        4
- 2 +     52
- 3 +   296

- FISH unamplified case
- 380 participants
- IHC scores:
- 0     275
- 1+    69
- 2+    27  (7%)
- 3+    10  (3%)

- Source: 2000 CYH 01, 02 and MK Surveys, CAP

## CAP MK B Survey Image Scoring

| Photo | Score | 0 | 1+ | 2+ | 3+ | Total |
| --- | --- | --- | --- | --- | --- | --- |
| 01 | 1+ | 25 | 352 | 80 | 0 | 457 |
| 02 | 2+ | 0 | 60 | 376 | 20 | 436 |
| 03 | 3+ | 8 | 0 | 3 | 445 | 456 |
| 04 | 1+ | 92 | 350 | 13 | 0 | 455 |
| 06 | 2+ | 7 | 133 | 282 | 33 | 455 |

- Score not provided for all images by all participants

## FISH vs IHC

- Specimen handling, adequacy not specified for either assay type; DNA less affected than protein
- FISH for Her2 has internal standard (Chr 17)
- Standard procedures and training are mandatory for laboratories performing FISH, but not required for all IHC assays
- Interpretation criteria are quantitative and clearly specified for FISH, ambiguous for IHC

## Conclusions

- Use of central laboratory during pivotal trial is necessary if there is not assay method standardization, standardized reference materials and training plans for assay and interpretation
- Interlaboratory comparison of assay and interpretation criteria should be conducted concurrently with pivotal trial
- Validated assay with standardized reference materials, training plan, and interpretation criteria is required prior to Phase III trial

## Treatment Guidelines for Patients with Negative Assay Results

- Assay should **not** be used to assign treatment if:
- Relationship between analyte and drug efficacy is unclear
- Interpretation guidelines of assay do not clearly specify  cut point of positive and negative
- Assay method is non validated
- Standardized reference materials are not available

## Package Insert Information

- Specific information about specimen adequacy and handling parameters
- Assay performance characteristics with assay comparisons, where appropriate
- Assay interpretation guidelines
- Acceptable methods of assay validation in a lab
- Acceptable levels of interlaboratory variability
- Requirement of laboratory participation in ongoing competency assessment

## Assay Utility Assessment

- Phase III clinical trials should be used to assess assay utility
- Tissue banking on such trials should be mandatory so that new assays can be validated on the same specimens
- TMAs can be created to promote new assay utility assessment while optimizing tissue bank specimen use.

## TMA Concordance with Slides 

| Arrays  | Head/Neck | Glioma | Prostate |
| --- | --- | --- | --- |
| One array | 90% | 86% | 86% |
| Two arrays
 | 95% | 93% | 93% |
| Three arrays
 | 99% | 95% | 93% |
| Four arrays
 | 100% | 97% | 97% |

- RTOG Study, presented USCAP, 2001; N= 150 tumors