Background:
Alternative diagnostic labels for melanoma in situ may better reflect its lower risk (15‑year survival 98%) compared to invasive melanoma (10-year survival ranging from 98% for AJCC stage IA to 19% for stage IV).
Design:
Secondary analysis of online randomised experiment in Australian adults without melanoma. Participants were randomised to a hypothetical diagnosis of “melanoma in situ (MIS)” (control), “low-risk melanocytic neoplasm”, or “low-risk melanocytic neoplasm, in situ” and completed a survey.
Outcomes:
Perceived risk measures: future invasive melanoma and mortality risk (0%–100%), comparative risk, affective risk, vulnerability (7-point Likert scales).
Calculated risk measures: lifetime invasive melanoma risk (from participants’ risk factors); melanoma mortality probability (Australian sex-age specific mortality rates).
Analysis:
Intention-to-treat analysis across randomised groups, unadjusted and adjusted for covariates (linear regression models).
Results:
1,668 adults were recruited. Compared to “MIS,” perceived melanoma mortality risk was lower for “low-risk melanocytic neoplasm” (−10.4%, 95% CI: −13.1% to −7.63%, p < .001) and for “low-risk melanocytic neoplasm, in situ” (−7.4%, 95% CI: −10.2% to −4.6%, p < .001). Similar patterns were observed for perceived risk of invasive melanoma, comparative, affective risk, and vulnerability. Participants in all groups substantially overestimated their lifetime risk of invasive melanoma (by 48.7%) and of dying from melanoma (by 32.0%) compared to the calculated risk; overestimation was lower in alternative label groups.
Conclusions:
Diagnostic labels without the word “melanoma” reduced risk overestimation, supporting MIS relabelling to mitigate overdiagnosis harm by reflecting its largely indolent nature.
Trial registration: ANZCTR: 386943