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are used to generate a standard curve [log (copy number) vs. threshold cycle (CT)], from which the unknown sample quantity is determined and then normalized against an internal reference (ideally ABL). The final result is usually reported as a percentage ratio (e.g., BCR-ABL/ABL).

Interpretation

The establishment of specific criteria to define molecular response, remission, and relapse has been difficult in light of the on-going evolution, and increasing sophistication, of quantitative technology, without universal technical standardization. Nevertheless, pertinent information can be ascertained.

With respect to monitoring postransplantation, several quantitative indicators emerge. Thus, a modified definition of molecular relapse has been proposed as rising or persistently high levels of BCR-ABL, delineated as a BCR-ABL/ABL ratio of >0.02% (-10"4), in two sequential specimens procured more than 4 months after asct.[17]

Although imatinib has shown encouraging results in the treatment of CML, the long-term correlates of clinical outcome remain to be defined. Nonetheless, recent studies suggest that quantitative RT-PCR values correlate with established cytogenetic response criteria and are associated with a differential short-term out-come.[18] In the IRIS study, a ''major molecular response (MMR)'' is defined as a > 3 log reduction in BCR-ABL/BCR levels compared to median pretreatment levels. Here, MMR was achieved in 39% of newly diagnosed CML patients after 12 months of imatinib as compared to only 2% of patients on interferon plus Ara-C.[10] Patients with this degree of molecular response to imatinib had a negligible risk of disease progression in the short-term.

One additional advantage of kinetic monitoring with imatinib is that it allows for the early recognition of therapeutic resistance. In this scenario, patients with a suboptimal therapeutic response may undergo screening for causative point mutations (e.g., using allele-specific

Fig. 2 Algorithms for the frequency of therapeutic monitoring in CML: (A) after allogeneic stem cell transplantation (ASCT), (B) with interferon-a, and (C) with imatinib mesylate therapy. [FISH, fluorescence in situ hybridization; mos, months; Ph, Philadelphia chromosome; PCR, qualitative reverse transcription polymerase chain reaction; Q-PCR, quantitative reverse transcription polymerase chain reaction; wk(s), week(s)].

oligonucleotide PCR), the identification of which could prompt implementation of alternative treatment strategies. Preliminary work with microarrays has identified differential gene expression profiles between patients with imatinib sensitivity and resistance.[19] In the future, this technology may predict therapeutic response and thus dictate front-line therapy.

Regardless of the therapeutic strategy, large prospective studies that correlate quantitative RT-PCR data with long-term clinical outcome are keenly anticipated. These investigations will direct the formulation of new guidelines to assist with the future therapeutic monitoring and clinical interpretation of these tests. Until then, a number of algorithms have been proposed for posttherapeutic monitoring (Fig. 2).[20,21] One final caveat in molecular RT-PCR analysis, whether qualitative or quantitative in methodology, is that it cannot assess the clonal evolution of disease. For this assessment, cytogenetic karyotypic analysis is required and must be performed every 6 months throughout the monitoring process regardless of the therapeutic modality employed. The emergence of cyto-genetically abnormal (but Ph-negative) clones with the use of imatinib further underscores the need for periodic conventional cytogenetic analysis.[22]

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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