Think before you shave: Factors influencing choice of biopsy technique for invasive melanoma and effect on definitive management.

Abstract

Partial biopsies are sometimes used for melanoma diagnosis with anticipated time and cost savings compared to excisional biopsy. However, their impact on subsequent melanoma management is unknown. Determine factors related to choice of partial over excisional biopsy to diagnose invasive melanoma and examine the effect of partial biopsies on definitive melanoma management. Retrospective repeated cross-sectional population-based study through the Victorian Cancer Registry of diagnosed melanomas in 2005, 2010 and 2015. A random sample of 400 patients per year, stratified by tumour thickness, was selected. A total of 1200 patients had 833 excisional and 337 partial biopsies. Omission of suspected diagnosis on pathology requests affected 46% (532/1151) of all diagnostic biopsies. Diagnostic suspicion did not influence preference for partial over excisional biopsy [Odds Ratio (OR) 1.2, 95%CI 0.8-1.7; P=0.40]. The partial:excisional biopsy usage ratio was higher in patients aged >50years than patients aged <50years [relative risk ratios (RRR) 1.5; 95%CI 1.0 to 2.2; P=0.03]. In 34% and 17% of tumours diagnosed with punch and shave, respectively, three procedures were required for definitive excision instead of two, compared with 5% of excisional biopsies When partial biopsy was used, patients were at greater risk of requiring three-staged excisions when controlled for age, anatomical site, melanoma subtype and thickness (RRR 6.7; 95%CI 4.4-10.1; P<0.001). Diagnostic suspicion does not appear to be a major factor influencing choice of biopsy technique. Using partial biopsy to diagnose melanoma often leads to an extra procedure for definitive treatment compared with excisional biopsy.