Melanoma classification gets a face-lift


By Mardi Chapman

2 Nov 2017

The introduction of a fourth sub-group to Stage 111 melanoma and a new M1d designation for central nervous system metastases are two of the key changes to the melanoma staging system from the American Joint Committee on Cancer (AJCC).

The evidence-based revision of the Tumor, Nodes, Metastasis (TNM) classification and melanoma stage grouping criteria, recently published in CA: A Cancer Journal for Clinicians, will guide patient treatment, provide better prognostic estimates, and refine stratification of patients entering clinical trials.

Professor Richard Scolyer, vice chairman of the AJCC Melanoma Expert Panel and conjoint medical director of the Melanoma Institute of Australia, told the limbic the new system was implemented in Australia this year and will come into effect in the US in 2018.  

It was developed from an analysis of a new international database of almost 50,000 patients diagnosed with stages I, II and III melanoma since 1998 across multiple institutions in the US, Australia and Europe.

“The risk stratification of patients into more accurate prognostic groups was based on contemporary melanoma patients rather than historic data. It allows clinicians to give more up-to-date and accurate estimations of risk for their patients.”

The 8th edition of the Cancer Staging Manual clarifies previous advice regarding tumor thickness measurements.

It says they should be recorded to the nearest 0.1 mm, not the nearest 0.01 mm, because of the impracticality and imprecision of measurements particularly for tumors over 1 mm thick.

“The old staging system implied you had to measure to 0.01mm. Agreement from the international melanoma pathology community was that it didn’t make a lot of practical sense,” Professor Scolyer said.

Definitions of T1a and T1b have been revised with mitotic rate no longer a criterion.

“Another issue was some clinicians were using T1b as a criteria to select patients to undergo sentinel lymph node biopsy and that was not following clinical management recommendations of various guidelines.”

“Realigning the T1a and T1b with a thickness cut off and presence of ulceration is better for sentinel lymph node biopsy.”

Professor Scolyer said it had became apparent in node positive disease, that it wasn’t just features of nodal tumour burden that were strong predictors of outcome.

“Features of the primary tumour still remain important predictors of outcome and for that reason prognostic stage III groupings are based on both involves both T parameters and N parameters.”

The increase from three to four stage lll subgroups aligns better with clinical management and clinical trial design, he said.

“There are important implications for patient counselling, for management and for the design, conduct and analysis of contemporary clinical trials.”

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