Sentinel lymph node biopsy rates in Victoria, 2018 and 2019

Sentinel lymph node biopsy (SLNB) is a staging procedure for assessing metastatic spread from a primary melanoma to the draining lymph nodes. In Australia, it is recommended that SLNB be considered for people with melanomas of Breslow thickness greater than 1.0 mm, or more than 0.8 mm for those with other high risk pathological features.1 Patients with a high risk primary melanoma and positive SLNB result are eligible for adjuvant systemic therapy. SLNB also allows risk stratification for guiding the frequency and extent of follow‐up. It has been reported that fewer than 50% of people with newly diagnosed invasive melanomas in Australia undergo SLNB.2,3

To provide more recent information on SLNB rates in Australia, we analysed aggregated Victorian Cancer Registry data for all people with newly diagnosed invasive melanoma in Victoria during the 2018 and 2019 calendar years. Formal ethics approval for our analysis was not required according to a memorandum of understanding with the registry.

During 2018 and 2019, 892 of 1855 people diagnosed with invasive melanomas of greater than 1.0 mm thickness (48%) and 151 of 597 with melanomas of 0.8–1.0 mm thickness (25%) underwent SLNB. In a logistic regression model adjusted for Breslow thickness, age group and sex, SLNB rates were similar in 2018 and 2019 (data not shown). Overall, 208 of 1050 SLNB results were positive (20%; expected range: 16–20%4), including 12 of 149 results for melanomas of 0.8–1.0 mm thickness (8%; expected range: 5–12%5). The proportions of people who underwent SLNB (22% v 17%) and of people with positive results (23% v 18%) were each higher for those under 60 years of age than for older people (Box). In a logistic regression model adjusted for Breslow thickness and age, SLNB rates were similar for men and women (data not shown).

Our findings suggest that the use of SLNB has not increased in Australia beyond previous reports,2,3 despite the availability of effective systemic therapy. Reasons may include the knowledge and beliefs of general practitioners and dermatologists,6 their views of the usefulness of SLNB,7 patient characteristics and preferences, and the local availability of radiography and surgeons trained in the procedure.6

However, attitudes to SLNB may be shifting.6 Recently introduced risk calculators facilitate personalised estimates of the risk of sentinel node involvement, based on age, Breslow thickness, histopathology subtype, mitotic rate, ulceration, and lympho‐vascular invasion.8 These calculators provide more personalised risk estimates than national guidelines with cut‐points based on Breslow thickness and ulceration alone. The calculators improve targeting of SLNB by distinguishing patients for whom positive SLNB results are more likely from those at lower risk, including people with melanomas of greater than 1 mm thickness but without high risk features.5 By improving the accuracy of staging, the calculators enable targeted access to adjuvant therapy.9 SLNB is typically recommended for patients with greater than 10% risk of nodal metastases, and can be considered for those with a 5–10% risk.8

Our study was limited by the fact that 40 SLNB results (4%) were unavailable, and because prognostic information about clinically positive nodes and some other melanoma characteristics were not included in the analysed dataset. Most cancer registries do not routinely collect these data, but they are important for evaluating clinical guideline adherence, melanoma treatment, health care use, and patient outcomes. Up‐to‐date evidence‐based information should be readily available to clinicians and patients for informing decisions about SLNB. The optimal use of online risk tools in practice, and barriers to patient access to SLNB, should be investigated.