The Society of Breast Imaging (SBI) has issued a statement regarding the Women Informed to Screen Depending on Measures of Risk (WISDOM) trial, results of which were published December 12 in JAMA.
The trial's conclusions are "unsupported," the society said, "due to significant methodological flaws," and "it remains uncertain whether risk-based screening is feasible for population-wide application." It listed the following concerns about the study:
- 40% of women declined randomization and participated in a separate observational cohort. "It is unclear why this large number of women declined randomization and why these women were given the choice to decline randomization," the SBI wrote.
- The study enrolled considerably fewer women than expected (28,372 women enrolled to be randomized, far fewer than the expected 65,000 women). "This limits the power of the study to detect differences in cancer rates," according to the society.
- The overall number of cancers was low (21 in the risk-based screening cohort and 31 in the annual mammogram screening cohort). "This outcome … suggests an underpowered study which cannot support its proposed conclusions," it explained.
- The study recorded only stage ≥ IIB breast cancers, which are often clinically detectable, the SBI wrote, noting that "annual screening detects cancers at earlier, non-palpable stages" and that "thus the exclusion of earlier stage breast cancers fails to acknowledge the critical benefit of screening mammography."
- "Contamination and noncompliance within the randomized cohorts was substantial," according to the SBI.
- "Risk-based screening led to more biopsies than annual screening, though the difference was nonsignificant," the society said. "Thus, risk-based screening did not reduce percutaneous needle biopsies."
- The study relied on self-reporting of cancers, biopsies, and imaging procedures. Patient self-reporting is an unreliable source of data, according to the SBI. It also noted that the study population was largely college-educated white women, which means the results "are not generalizable across the population."
The society did praise the study for the fact that the "risk-based screening cohort were counseled to implement risk-reducing strategies," but noted that "even with this intervention, adherence to risk-reducing strategies was poor."
"Ultimately, risk-based breast cancer screening could theoretically help to personalize screening regimens for all women and triage precious medical resources to maximize population benefit, a goal which the SBI supports in principle," it concluded. "However, the contaminated and underpowered WISDOM trial has not demonstrated a reliable pathway for systematic implementation and effective risk-based screening regimens. Therefore, the SBI continues to recommend annual mammogram screening starting at age 40 for all women at average risk, which confers the greatest mortality benefit."
