Patients' understanding of how genotype variation affects benefits of tamoxifen therapy for breast cancer.
BACKGROUND
CYP2D6 is a critical enzyme in the metabolism of tamoxifen and potentially a key determinant in breast cancer outcomes. Our study examined patients' beliefs about how the CYP2D6 genotype would affect their prognoses.


METHODS
Women enrolled in a pharmacogenomic clinical trial and on tamoxifen for prevention or treatment of breast cancer underwent CYP2D6 genotyping (EM = extensive, IM = intermediate, PM = poor metabolizing alleles). The informed consent said that the purpose of the trial was to examine effects of dose adjustment based on genotype, but that clinical benefits were uncertain. Our embedded sub-study surveyed 320 patients prior to receiving their genotypes. We experimentally manipulated 6 vignettes to describe hypothetical tamoxifen treatment (no or yes) and hypothetical genotype (EM, IM or PM). For each vignette, women gave their perceived recurrence risk (RR; 0-100%).


RESULTS
Women believed that genotype would not affect their RR if they did not take tamoxifen (p = 0.06). However, women believed that if prescribed tamoxifen, genotype would affect their RR (22% if EM, 30% if IM and 40% if PM, p < 0.001).


CONCLUSIONS
Women believed that extensive tamoxifen metabolizers had better prognoses, despite study materials stating uncertainty about any benefit. The rapidly changing nature of genomic science calls for caution when communicating clinical utility.
Department of Health Behavior, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, N.C., USA.
N T
NT
Brewer
J T
JT
Defrank
W K
WK
Chiu
J G
JG
Ibrahim
C M
CM
Walko
P
P
Rubin
O A
OA
Olajide
S G
SG
Moore
R E
RE
Raab
D R
DR
Carrizosa
S W
SW
Corso
G
G
Schwartz
J M
JM
Peppercorn
H L
HL
McLeod
L A
LA
Carey
W J
WJ
Irvin
D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000523:psychology*; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005838:Genotype; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000235:genetics / Q000523:psychology*; D010353:Patient Education as Topic / Q000379:methods*; D010597:Pharmacogenetics; D011379:Prognosis; D013629:Tamoxifen / Q000627:therapeutic use
D018931:Antineoplastic Agents, Hormonal; D013629:Tamoxifen; D019389:Cytochrome P-450 CYP2D6