Bath Cancer Research

Bath Cancer Research DiSC assay for CLL endorsed by US government panel

In 1999 two US companies selling drug response testing services applied to the US government's Medicare Coverage Advisory Committee (MCAC) to have Human Tumour Assay Systems (HTAS) reimbursed by Medicare. HTASs or drug response assays are laboratory tests that identify individual patient response to anticancer drugs (because cancer is a heterogeneous disease treatment must be tailored to the individual). A hearing was arranged where interested parties could present evidence to a MCAC panel about HTASs. The panel of experts spent two days hearing wide-ranging evidence about the benefits and limitations of drug response testing.

Dr Andrew Bosanquet, Director of Bath Cancer Research, presented his work with chronic lymphocytic leukaemia (CLL). Complimentary comments were made about Dr Bosanquet's work with the DiSC assay (a drug sensitivity test) in haematological malignancies - an "elegant" 10-year study with fludarabine in CLL was thought to show "very good evidence of clinical utility". Work with other assay systems and solid tumours was seen as having conflicting results and not adequately addressing survival.

Dr Bosanquet supported Dr Robert Nagourney from California who maintained that the different drug response technologies encompassed by the catch-all "HTAS" should be assessed separately. Technologies like the DiSC assay look at cell death or apoptosis and can accurately discriminate between sensitivity and resistance to a drug. Older technologies and their descendants look at inhibition of cell proliferation and identify extreme drug resistance. This important distinction between the two different technologies was eloquently addressed by Dr Elizabeth Panke, a pathologist and ovarian cancer patient.

Dr Panke was treated with standard ovarian chemotherapy - carboplatin + taxol, then topotecan - her tumour grew rapidly and ascites developed. She wanted drug response data to identify effective treatment and, aware of the different technologies available, sent malignant cells to two US companies. She received two very different sets of results. The inhibition of cell proliferation (or extreme drug resistance - EDR) test (predictive accuracy 74%) found her cells not resistant to most drugs tested and least resistant to carboplatin, taxol and topotecan. Results from the DiSC assay (predictive accuracy 83%) found her cells resistant to carboplatin, taxol and topotecan and most drugs tested but sensitive to cisplatin + gemcitabine combination. Cisplatin + gemcitabine had Dr Panke's ascites under control in two weeks and her tumour marker fell by two thirds.

This distinction between testing systems was not welcomed by those selling EDR inhibition of cell proliferation technologies but accepted by the MCAC panel. Consequently, the application for Medicare coverage may be withdrawn and DiSC assays for CLL not covered. However, recognising the quality of research from Dr Bosanquet's labs, the MCAC unanimously concluded that "HTASs demonstrate clinical utility for directing treatment of CLL".

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