Assessment of the time-tradeoff values for prophylactic mastectomy of women with a suspected genetic predisposition to breast cancer

Background. Female carriers of the breast-cancer-susceptibility genes BRCA1 and BRCA2 are at high risk for breast cancer (85%). They face the choice between prophylactic mastectomy (PM) and breast cancer screening. For this treatment choice, a shared-decision-making program was developed. In this program, the time tradeoff (TTO) was used to assess preferences for PM. Purpose. Assessment of the feasibility, constant proportional tradeoff, and reliability of using the TTO for this purpose. Methods. Fifty-four women suspected to carry the BRCA1/2 mutation were provided with comprehensive relevant information. Their preferences for PM were assessed on two occasions. Discrepancies between preferences indicated by the two tests were resolved by testing a third time. The preferences assessed on the last occasion were used for individual decision analyses. In order to test constant proportional tradeoff, the TTO consisted of four items with different numbers of life years. Results. Forty-two women (78%) completed the TTO twice and nine women (17%) performed the test a third time. Three women (5%) completed the TTO only once. The mean TTO value for PM at the last replication was 0.69 (SD = 0.30). Violations of constant proportional tradeoff were significant: the largest tradeoffs were recorded for the shortest durations. Pearson's correlation coefficient between the TTO values for the two last sessions was 0.96. Conclusion. Assessment of individual preferences by the TTO in this patient group is feasible and reliable. Therefore, the TTO can be used in clinical settings to elicit treatment preferences of women proven or suspected to have a genetic predisposition to breast cancer.