Impact of prior treatment with immune checkpoint inhibitors on dacarbazine efficacy in metastatic melanoma

BACKGROUND

Despite its low efficacy, chemotherapy with dacarbazine remains an option in metastatic melanoma patients after failure of immune checkpoint inhibitors (ICI) ± targeted therapy. Some observations suggested an increased efficacy of chemotherapy in melanoma or lung cancer patients previously treated with ICI; we aimed to evaluate the efficacy of dacarbazine in a controlled-group study of patients pre-treated or not with ICI.

METHODS

We retrospectively collected data from all consecutive patients treated with dacarbazine for advanced cutaneous melanoma without brain metastasis, in our skin cancer centre between June 2006 and September 2019. The primary endpoint was progression-free survival (PFS); secondary endpoints were overall response rates (ORR), overall survival (OS) and safety of dacarbazine.

RESULTS

Among 72 patients, 17 (23.6%) received dacarbazine after ICI and 55 (76.3%) without prior ICI. Despite less favourable prognostic factors in patients ICI-pre-treated, median PFS was 4.27 months (range 0.89-43.69) in this group versus 2.04 months (range 1.25-39.25) P = 0.03 in non-ICI-pre-treated patients; ORR were 35.3% and 12.7%, respectively. The median OS and the occurrence of adverse events were similar in both groups.

CONCLUSION

Dacarbazine seems to offer a short-lived benefit in patients with progressive advanced disease despite ICI (±targeted therapy), and could be an alternative before considering best supportive care.

Second primary melanoma in advanced melanoma patients treated with anti-PD-1 monoclonal antibodies

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Background: Development of a second primary melanoma (SCPM) has not been reported in melanoma patients treated with anti-PD-1 monoclonal antibodies (mAb), in contrast with those reported in BRAF-inhibitor-treated patients. Our aim was to report arising SCPM in patients with advanced melanoma treated with anti-PD-1 therapy. Methods: Retrospective study, conducted in 2 referral centres, including advanced melanoma patients who developed a SCPM after anti-PD-1 mAb initiation, between September 2010 and May 2019. BRAF or NRAS mutational status was assessed by targeted NGS panels, real-time PCR, and immunohistochemistry. Results: Among a total of 509 patients treated with anti-PD-1 mAb, 4 had a SCPM (incidence: 0.8%; 95%CI: 0.02-1.57%). All patients were treated with nivolumab, in first (N = 3) or second line after progression with BRAF + MEK inhibitors (N = 1). No immune-related adverse event greater than grade 2 according to Common Terminology Criteria for Adverse Events version 5.0. was observed in these 4 cases; a vitiligo-like depigmentation (grade 1) was observed in two patients. The median time from the first nivolumab infusion to the SCPM diagnosis was 17.5 months (range: 5-21). All patients developed the SCPM after achieving a complete response. Nivolumab administration had been discontinued (4 months prior) in one patient. Histology revealed 4 superficial spreading melanomas (SSM): one invasive (without BRAFV600 mutation) and 3 intraepidermal melanomas (2 with a BRAFV600E mutation and one with a NRASQ61H mutation). 3 patients had risk factors for developing multiple melanomas: a dysplastic nevus syndrome, a high number of nevi (≥100 nevi), and a family history of melanoma in first-degree relatives and constitutional heterozygous mutation of exon 2 of the CDKN2A gene. Occurrence of SPCM did not alter advanced melanoma treatment. With a median follow-up of 29 months [range: 18-41] from the first anti-PD-1 mAb infusion, all patients had prolonged CR, and treatment was discontinued in all patients, without relapse after a median 11.5 months [0-18] off therapy. The median duration of nivolumab treatment was 15.5 months [10-24]. Conclusions: Although anti-PD-1 mAb could theoretically decrease the risk of developing another melanoma in metastatic melanoma patients, we found 4 such cases, highlighting the importance of regular clinical screenings for new primary melanoma in patients with metastatic melanoma even when responsive to anti-PD-1 therapy. Immune checkpoint inhibitors do not totally prevent the risk of occurrence a SCPM.