IMPORTANCE Neoadjuvant checkpoint inhibition in patients with high-risk stage III melanoma shows high pathologic response rates associated with a durable relapse-free survival. Whether a... Show moreIMPORTANCE Neoadjuvant checkpoint inhibition in patients with high-risk stage III melanoma shows high pathologic response rates associated with a durable relapse-free survival. Whether a therapeutic lymph node dissection (TLND) can be safely omitted when a major pathologic response in the largest lymph node metastasis at baseline (index lymph node; ILN) is obtained is currently being investigated. A previous small pilot study (n = 12) showed that the response in the ILN may be representative of the pathologic response in the entire TLND specimen.OBJECTIVE To assess the concordance of response between the ILN and the total lymph node bed in a larger clinical trial population.DESIGN, SETTING, AND PARTICIPANTS Retrospective pathologic response analysis of a multicenter clinical trial population of patients from the randomized Study to Identify the Optimal Adjuvant Combination Scheme of Ipilimumab and Nivolumab in Melanoma Patients (OpACIN) and Optimal Neo-Adjuvant Combination Scheme of Ipilimumab and Nivolumab (OpACIN-neo) trials. Included patients were treated with 6 weeks neoadjuvant ipilimumab plus nivolumab. Patient inclusion into the trials was conducted from August 12, 2015, to October 24, 2016 (OpACIN), and November 24, 2016, and June 28, 2018 (OpACIN-neo). Data were analyzed from April 1, 2020, to August 31, 2021.MAIN OUTCOMES AND MEASURES Concordance of the pathologic response between the ILN and the TLND tumor bed. The pathologic response of the ILN was retrospectively assessed according to the International Neoadjuvant Melanoma Consortium criteria and compared with the pathologic response of the entire TLND specimen.RESULTS A total of 82 patients treated with neoadjuvant ipilimumab and nivolumab followed by TLND (48 [59%] were male; median age, 58.5 [range, 18-80] years) were included. The pathologic response in the ILN was concordant with the entire TLND specimen response in 81 of 82 patients (99%) and in 79 of 82 patients (96%) concordant when comparing the ILN response with the response in every individual lymph node. In the single patient with a discordant response, the ILN response (20% viable tumor, partial pathologic response) underestimated the entire TLND specimen response (5% viable, near-complete pathologic response). Two other patients each had 1 small nonindex node that contained 80% viable tumor (pathologic nonresponse) whereas all other lymph nodes (including the ILN) showed a partial pathologic response. In these 2 patients, the risk of regional relapse might potentially have been increased if TLND had been omitted.CONCLUSIONS AND RELEVANCE The results of this study suggest that the pathologic response of the ILN may be considered a reliable indicator of the entire TLND specimen response and may support the ILN response-directed omission of TLND in a prospective trial. Show less
Background: Guidelines for pathological evaluation of neoadjuvant specimens and pathological response categories have been developed by the International Neoadjuvant Melanoma Consortium (INMC). As... Show moreBackground: Guidelines for pathological evaluation of neoadjuvant specimens and pathological response categories have been developed by the International Neoadjuvant Melanoma Consortium (INMC). As part of the Optimal Neo-adjuvant Combination Scheme of Ipilimumab and Nivolumab (OpACIN-neo) clinical trial of neoadjuvant combination anti-programmed cell death protein 1/anti-cytotoxic T-Iymphocyte-associated protein 4 immunotherapy for stage III melanoma, we sought to determine interobserver reproducibility of INMC histopathological assessment principles, identify specific tumour bed histopathological features of immunotherapeutic response that correlated with recurrence and relapse-free survival (RFS) and evaluate proposed INMC pathological response categories for predicting recurrence and RFS.Patients and methods: Clinicopathological characteristics of lymph node dissection specimens of 83 patients enrolled in the OpACIN-neo clinical trial were evaluated. Two methods of assessing histological features of immunotherapeutic response were evaluated: the previously described immune-related pathologic response (irPR) score and our novel immunotherapeutic response score (ITRS). For a subset of cases (n = 29), cellular composition of the tumour bed was analysed by flow cytometry.Results: There was strong interobserver reproducibility in assessment of pathological response (kappa = 0.879) and percentage residual viable melanoma (intraclass correlation coefficient = 0.965). The immunotherapeutic response subtype with high fibrosis had the strongest association with lack of recurrence (P = 0.008) and prolonged RFS (P = 0.019). Amongst patients with criteria for pathological non-response (pNR, >50% viable tumour), all who recurred had >= 70% viable melanoma. Higher ITRS and irPR scores correlated with lack of recurrence in the entire cohort (P = 0.002 and P <= 0.0001). The number of B lymphocytes was significantly increased in patients with a high fibrosis subtype of treatment response (P = 0.046).Conclusions: There is strong reproducibility for assessment of pathological response using INMC criteria. Immunotherapeutic response of fibrosis subtype correlated with improved RFS, and may represent a biomarker. Potential B-cell contribution to fibrosis development warrants further study. Reclassification of pNR to a threshold of >= 70% viable melanoma and incorporating additional criteria of <10% fibrosis subtype of response may identify those at highest risk of recurrence, but requires validation. Show less
