Page 473 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 23 ■ Myeloproliferative Neoplasms 457

Cytogenetic response correl tes with incre se surviv l, PCR ppro ch, lthough levels th t re un etect ble by re l-

n p tients show ecre se in the presence o Ph chro- ti e PCR so eti es nee to be v li te by two-step neste

oso es by cl ssic k ryotyping o bone rrow cells. T is re l-ti e PCR.

etho is ble to etect 1 Ph-positive cell in 25 to 30 nor-

l cells (3% to 4% sensitivity) but c nnot etect ini l Prognostic Signi cance of Cytogenetic and

resi u l ise se in peripher l bloo . Fluorescence in situ Molecular Responses

hybri iz tion (FISH) c n etect BCR-ABL–positive cells Currently, the gol st n r or ev lu ting p tient response

with sensitivity o 1 in 200 to 500 nor l cells in either to tre t ent is convention l cytogenetic n lysis. Molecul r

bone rrow or peripher l bloo (Fig. 23.8). Another response is e erging s key en point or clinic l tri ls

incre se in sensitivity is chieve with re l-ti e PCR, which (Fig. 23.8) n y beco e key clinic l n ge ent tool.

uses pri er- plif e DNA to etect the BCR-ABL usion It h s been est blishe th t—p rticul rly or p tients

t the RNA level n ev lu tes the r tio o BCR-ABL RNA tre te with IFN-α, the f rst biologic l gent c p ble o

tr nscripts in bone rrow or peripher l bloo . R -PCR in ucing signif c nt nu ber o cytogenic re issions in

c n etect one leuke ic cell in 10 to 10 nor l cells. An CML—the egree o tu or lo re uction uring ther py is
4
3
even ore sensitive v ri tion o this technique is two-step n i port nt prognostic ctor.

neste re l-ti e PCR, using two roun s o R -PCR. It is T ree i erent levels o response c n be i erenti te .

ble to etect BCR-ABL tr nscripts in 1 o 10 cells without T e he tologic l response is chieve with the nor l-
6
qu nti ying the level o tr nscripts. Neste R -PCR is use ul iz tion o peripher l bloo counts n bsence o signs n

when other test results (inclu ing re l-ti e PCR) beco e sy pto s o ise se. T e cytogenetic responses est blishe

neg tive. In clinic l pr ctice, qM n (Applie Biosyste s on the b sis o the proportion o resi u l Ph-positive et -

qM n Foster City, C li orni ) or LightCycler (LightCycler, ph ses re ef ne s co plete (0% o et ph ses), p rti l

Roche Di gnostics Corp. In i n polis, In i n ) re l-ti e (1% to 33%), inor (34% to 66%), or ini l (67% to 99%).

PCR is now l rgely repl cing the nonqu ntit tive re l-ti e A jor response represents the su o the co plete n

p rti l cytogenetic responses. Molecul r re ission is tr i-

tion lly ef ne on the b sis o the etection o resi u l BCR-
Leukemic Burden Response ABL mRNA tr nscripts by qu lit tive R -PCR.

10 13 hematologic remission
Resistance in Chronic Myelogenous Leukem ia

10 12 Resist nce h s been observe in proportion o p tients er

v ri ble perio s o i tinib onother py. P tients in the

2 logs 10 11 cytogenic remission Ph positive 0% chronic ph se h ve respon e to i tinib ther py or ore
th n 2 ye rs, but ost respon ing p tients in bl st crisis y

10 10 experience rel pse e rly espite continue ther py. Clinic l

ech nis s o i tinib resist nce c n be ivi e into two

groups: (1) re ctiv tion o BCR-ABL with continuing epen-
4 logs 10 9 molecular remission PCR positive
ence on BCR-ABL sign ling n (2) re ining inhibition

10 8 but BCR-ABL sign ling is byp sse by ltern tive sign ling
p thw ys. In the l tter c se, resist nce y be c use by the

10 7 evolution o the ise se with occurrence o novel nu eric or

structur l cytogenetic berr tions [e.g., triso y 8, iso(17q)],
10 6
which le to BCR-ABL–in epen ent proli er tion o leuke-

ic cells.

10 5 molecular remission PCR negative T e evelop ent o i tinib resist nce presents new

ther peutic ch llenges. T e ct th t BCR-ABL is ctive in
10 4
ny i tinib-resist nt p tients suggests th t the chi eric

10 3 oncoprotein re ins r tion l rug t rget. Knowle ge o
the ut tions shoul per it the evelop ent o n ss y to

10 2 etect rug-resist nt clones be ore clinic l rel pse occurs.

10 1
Leukemia-Speci c Targets

10
Leuke i -specif c t rgets y involve leuke i -specif c

0 pepti es th t e i te gr -versus-leuke i e ect. In

FIGURE 23.8 Sche tic illustr tion o ther peutic response o CML, the only unique ino ci is the one or e by the
CML p tients on cytogenetic n olecul r level. (Fro S glio G. novel co ons t the b2- 2 or b3- e junctions in the BCR-ABL

Me suring olecul r response in CML: proble s n signif c nce, proteins. Evi ence pro uce by ss spectro etry v li tes

8th EHA Congress, June 2003.) th t CML cells o express this leuke i -specif c pepti e