External Medicine
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Melanoma: Staging/Prognosticating
SENTINEL LYMPH NODE BIOPSY
Predicting SLN Positivity
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The Melanoma Institute of Australia created a nomogram based on clinical factors to predict patients who are likely to have a positive sentinel node (here), and validated it in a cohort of ~60K US patients. It showed an ROC C-statistic of 0.733, indicating a good, but not strong predictive model. 37454700
Risks and benefits of SNLBx
Sharon CE, Straker RJ 3rd, Gimotty PA, Chu EY, Mitchell TC, Miura JT, Marchetti MA, Bartlett EK, Karakousis GC. Sentinel lymph node biopsy status improves adjuvant therapy decision-making in patients with clinical stage IIB/C melanoma: A population-based analysis. J Am Acad Dermatol. 2023. PMID: 36442639.
MY SUMMARY: This is a challenging study to comprehend statistically, but conceptually it sought to weigh the risks and benefits of SLNBx for patients with stage IIB/C melanoma for whom adjuvant immunotherapy is FDA approved. The challenge with answering the question is the variability of recommendations by oncologists for adjuvant immunotherapy, which often hinges on the risk of melanoma specific death. The conclusion was that if sentinel lymph node biopsy is completed and used as a prognostic variable in contrast to using clinicopathologic factors alone to estimate melanoma specific death, treatment recommendations will be more accurate. Numerically: 6 of 100 patients will avoid immunotherapy without missing the treatment of those destined to recur. When considering patients <65yo, this was 11 of 100 patients.
31-GENE EXPRESSION PROFILE
Podlipnik S, Martin BJ, Morgan-Linnell SK, Bailey CN, Siegel JJ, Petkov VI, Puig S. The 31-Gene Expression Profile Test Outperforms AJCC in Stratifying Risk of Recurrence in Patients with Stage I Cutaneous Melanoma. Cancers (Basel). 2024. PMID: 38254778.
MY SUMMARY: Cohort of AJCC Stage IA and IB tumors. Found 31-GEP better predicts recurrence and melanoma specific survival than AJCC IA or IB classification. All classes of GEP (1A, 1B/2A, and 2B) all predicted recurrence. Only 2B was an independent predictor of survival.
Not sure how much this would help clinically. Survival even for class 2B (highest 31-GEP risk) patients was over 90%. There may be some fringe benefit to modifying the psychology of getting a melanoma diagnosis but the value in management is not apparent. They did not evaluate value in predicting SLNBx positivity, and didn't appear to differentiate T1a tumors with high risk factors from those without.
In this study, if you had a T1a tumor you had an ~16% chance of getting a Class 2B result. If you were T1b you had a ~23% chance.