Number of excised lymph nodes as a quality assurance measure for lymphadenectomy in melanoma.

Importance: Although the number of excised lymph nodes (LNs) represents a quality assurance measure in lymphadenectomy for many solid tumors, the minimum number of LNs to be dissected has not been established for melanoma.
Objective: To investigate the distribution of the number of excised LNs in a large patient series (N = 2526) to identify values that may serve as benchmarks for monitoring the quality of lymphadenectomy in patients with melanoma.
Design, Setting, and Participants: A retrospective multicenter study was conducted (1992-2010) in tertiary referral centers for treatment of cutaneous melanoma. Medical records on 2526 patients who underwent lymphadenectomy for regional LN metastasis associated with cutaneous melanoma were examined.
Exposure: Patients had undergone lymphadenectomy for regional LN metastasis.
Main Outcomes and Measures: The mean, median, and 10th percentile of the number of excised LNs were calculated for the axilla (3 levels), neck (≤3 or ≥4 dissected levels), inguinal, and ilioinguinal LN fields.
Results: After 3-level axillary (n = 1150), 3-level or less neck (n = 77), 4-level or more neck (n = 135), inguinal (n = 209), and ilioinguinal (n = 955) dissections, the median (interquartile range [IQR]) and mean (SD) number of excised LNs were as follows: 3-level axillary dissection, 20 (15-27) and 22 (8); 3-level or less neck, 21 (14-33) and 24 (15); 4-level or more neck, 29 (21-41) and 31 (14); inguinal, 11 ( 9-14) and 12 (5); and ilioinguinal, 21 (16-26) and 22 (4). A total of 90% of the patients had 12, 7, 14, 6, and 13 excised LNs (10th percentile of the distribution) after 3-level axillary, 3-level or less neck, 4-level or more neck, inguinal, and ilioinguinal dissections, respectively. More excised LNs were detected in younger (21 for those <54 years of age and 19 for ≥54 years, P < .001) and male (21 for male sex and 19 for female sex, P < .001) patients from high-volume institutions (21 for volume of ≥300 vs 18 for volume <300, P < .001) with a more recent year of diagnosis (21 for years 2002-2010 vs 18 for years 1992-2001, P < .001), LN micrometastasis vs macrometastasis (20 vs 19, P = .005), and more positive LNs (R² = 0.03, P < .001); however, the differences between median values were small.
Conclusions and Relevance: These minimum numbers of excised LNs are reproducible across the institution, patient, and tumor factors evaluated. They can be taken into consideration when monitoring the quality of lymphadenectomy in melanoma and can represent entry criteria for randomized trials investigating adjuvant therapies.