Manual microdissection to remove biopsy cavities from breast cancer specimens essential

Genomic Health, Inc. (Nasdaq: GHDX) today announced results from a study demonstrating the critical role of manual microdissection to remove all biopsy cavities from breast cancer specimens. Genomic Health's Oncotype DX is the only commercially available breast cancer test that employs manual microdissection following review by a board certified surgical pathologist with breast expertise to predict a patient's benefit from chemotherapy and risk of disease recurrence. This study was discussed in a poster presentation at the ASCO 2009 Breast Cancer Symposium in San Francisco.

Oncotype DX measures the expression of 21 genes of an individual tumor removed during surgery to generate a Recurrence Score result that quantifies the magnitude of chemotherapy benefit and the likelihood of recurrence for early-stage breast cancer patients. The Oncotype DX assay is performed on tumor tissue removed either by core biopsy, a commonly used diagnostic procedure for the initial diagnosis of breast cancer, or by surgery, lumpectomy or mastectomy. Since many tumor specimens removed by lumpectomy or mastectomy contain biopsy cavities researchers conducted this study to determine whether the presence of these cavities impacts gene expression and recurrence risk assessment.

"This analysis confirms that the inclusion of biopsy cavities in breast cancer specimens is associated with significant changes in the expression of individual genes, and can ultimately drive the Recurrence Score result higher," said Theodore Miller, MD, professor of pathology at the University of California San Francisco Medical Center. "The removal of biopsy cavities by manual microdissection is warranted by the study's findings and should be practiced as part of any molecular breast cancer diagnostic platform that assesses risk of recurrence by examination of tumor tissue."

The study assessed 53 invasive breast carcinomas (19 well-, 19 moderately-, and 15 poorly-differentiated) to determine differences in gene expression between whole sections that contained biopsy cavities, enriched tumors where biopsy cavities were excluded and the dissected biopsy cavities. Standardized quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis for the 21 genes was performed.

The results indicated that there was a statistically significant average increase in the Recurrence Score result for whole sections versus enriched tumors (5.35 Recurrence Score Units; p < .0001). There were also statistically significant differences in reference normalized gene expression between enriched tumor and whole sections in 12 of the 16 cancer-related genes. Additionally, biopsy cavities tended to have high-risk Recurrence Scores.

"Careful histologic review of each patient case by a board-certified surgical pathologist and manual microdissection to remove all biopsy cavities when necessary has been standard practice in our lab since the Oncotype DX test became available in 2004," said Rick Baehner, MD, director of pathology at Genomic Health and assistant professor of clinical pathology at the University of California San Francisco Medical Center. "This study underscores the critical role that expert pathologists play in working with the clinical laboratory to provide the most accurate molecular assessment of individual tumors so that physicians and patients can make well-informed individual treatment decisions."

Also presented at this week's Breast Cancer Symposium were results of a multi-center Japanese study demonstrating that the Oncotype DX breast cancer test had significant prognostic value in Japanese women with estrogen receptor-positive early-stage breast cancer. In this study that was originally presented at the 2009 Kyoto Breast Cancer Consensus Conference International Convention, Oncotype DX identified a large portion of patients in Japan who had estrogen receptor-positive early-stage breast cancer as having a low likelihood of distant recurrence.