Blood cancers

High dose cyclo ruled out in PBSC mobilisation

Granulocyte-colony stimulating factor (G-CSF) plus cyclophosphamide at high dose is not warranted for peripheral blood stem cell mobilisation after bortezomib-based induction in transplant-eligible patients with multiple myeloma, an Australian study shows.

A review of outcomes in 288 patients across six centres in Victoria found a non-significant difference in stem cell yield between patients receiving G-CSF and cyclophosphamide at 1.5-2 g/m2 or the higher dose of 3-4 g/m2.

Study author Dr Chong Chyn Chua told the limbic the higher dose may have been more useful when myelosuppressives such as melphalan and thalidomide which tended to reduce stem cell yield were more commonly used.

“So we think in this era where we are using more novel agents we might not need to use such a high dose of cyclophosphamide,” she said.

Dr Chua, from Austin Health, said the higher dose treatment also resulted in more febrile neutropenia and hospital admissions.

“So overall we feel that the high dose cyclophosphamide doesn’t really add much benefit – not much extra yield – and we think the standard dose is a better option for those patients.”

The study also compared G-CSF alone with the combination treatment and found stem cell yield was improved by the addition of cyclophosphamide. Median total yield was 5.3 x 106/kg with G-CSF alone versus 9.2 x 106/kg with the addition of cyclophosphamide.

The proportion of patients achieving target levels of mobilisation with one or two aphereses without rescue (69 v 88%) and overall with a plerixafor salvage (83 v 95%) was also improved with cyclophosphamide.

“With G-CSF alone you don’t have additional chemo exposure and you are not at risk of having neutropenia. And with G-CSF alone, if the institution can access plerixafor, which is one of the newer mobilisation medications, that actually helps.”

“The problem with plerixafor is that it is not accessible on PBS if you are just mobilized by G-CSF alone.”

Dr Chua said the study was not large enough to definitely say which mobilisation strategy was better. The decision came back to weighing up the risk and benefits for individual patients.

“At the moment in Victoria, physician or institutional preferences dictates which regimen is used.”

She added that from a practical point of view the day of collection was less predictable when mobilising with G-CSF plus cyclophosphamide than G-CSF alone.

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