Treatment Outcomes for Metastatic Melanoma of Unknown Primary in the New Era: A Single-Institution Study and Review of the Literature

Maximal surgical tumour load reduction in immune-checkpoint inhibitor naïve patients with melanoma brain metastases correlates with prolonged survival

BACKGROUND

Recent therapeutic advances in metastatic melanoma have led to improved overall survival (OS) rates, with consequently an increased incidence of brain metastases (BM). The role of BM resection in the era of targeted and immunotherapy should be reassessed. In the current study we analysed the role of residual intracranial tumour load in a cohort of melanoma BM patients.

METHODS

Retrospective single-centre analysis of a prospective registry of resected melanoma BM from 2013 to 2021. Correlations of residual tumour volume and outcome were determined with respect to patient, tumour and treatment regimens characteristics.

RESULTS

121 individual patients (66% male, mean age 59.9 years) were identified and included in the study. Pre- and postoperative systemic treatments included BRAF/MEK inhibitors, as well as combination or monotherapy of immune-checkpoint inhibitors (ICIs). Median OS of the entire cohort was 20 months. Cox proportional-hazard analysis revealed postoperative anti-CTLA4+anti-PD-1 therapy (HR 0.07, p = .01) and postoperative residual intracranial tumour burden (HR 1.4, p = .027) as significant predictors for OS. Further analysis revealed that ICI-naïve patients with residual tumour volume ≤3.5 cm³ and postoperative ICI showed significantly prolonged OS compared to patients with residual volume >3.5 cm³ (p < .0001). Subgroup analysis of ICI-naïve patients showed steroid intake postoperatively to be negatively associated with OS, however residual tumour volume ≤3.5 cm³ remained independently correlated with superior OS (HR 0.14, p < .001).

CONCLUSION

Besides known predictive factors like postoperative ICI, a maximal intracranial tumour burden reduction seems to be beneficial, especially in ICI-naïve patients. This highlights the importance of local CNS control and the need to further investigating the role of initial surgical tumour load reduction in randomised clinical trials.

Treatment of Metastatic Melanoma at First Diagnosis: Review of the Literature

Metastatic melanoma (MM) is a pathological entity with a very poor prognosis that, until a few decades ago, had a low response rate to systemic treatments. Fortunately, in the last few years, new therapies for metastatic melanoma have emerged. Currently, targeted therapy and immunotherapy are the mainstays of the therapeutic arsenal available for patients with unresectable or metastatic melanoma. However, both clinical evolution and drug efficacy in melanoma patients are very different depending on the stage at which it is diagnosed. In fact, the aggressiveness of melanoma is different depending on whether it debuts directly as metastatic disease or if what occurs is a relapse after a first diagnosis at an early stage, although the biological determinants are largely unknown. Another key aspect in the clinical management of metastatic melanoma at first diagnosis strives in the different prognosis of melanoma of unknown primary (MUP) compared to melanoma of known primary (MPK). Understanding the mechanisms behind this, and the repercussion of implementing targeted and immune therapies in this specific form is crucial for designing diagnosis and treatment decision algorithms that optimize the current strategies. In this review article, we recapitulate the information available thus far regarding the epidemiology and response to immunotherapy treatments or targeted therapy in patients diagnosed with metastatic melanoma as a first diagnosis, with especial emphasis on the emerging specific information of the subpopulation formed by MUP patients.

Hypothesised cutaneous sites of origin of stage III melanomas with unknown primary: A multicentre study

Based on molecular evidence that melanomas with unknown primary (MUPs) arise from the skin, we hypothesised that sites of MUPs are disproportionately on trunk and lower limbs, sites that are not readily visible to patients and clinicians. We tested this hypothesis by inferring the anatomic site of origin of MUPs from the corresponding known cutaneous sites of melanoma patients with known primary tumours (MKPs). We analysed data from three separate cohorts of patients from Brisbane, Australia (n = 236); Manchester, UK (n = 51) and Padova, Italy (n = 33), respectively, who first presented with stage III melanoma with lymph node metastases. We matched two MKP patients to each MUP patient based on lymph node dissection (LND) site, age and sex, and imputed cutaneous sites of origin of MUPs from their two matched MKPs for study countries, giving two possible sites for each MUP per centre. Overall, results showed that MUP patients were predominantly male, and trunk was the most likely origin, comprising around a third to a half of MUPs across the three cohorts. The remaining MUP inferred sites varied by country. In the Australian cohort, the legs accounted for a third of imputed sites of MUPs, while in the UK and Italian cohorts, the most frequent site was the arms followed by the legs. Our findings suggest the need for regular and thorough skin examination on trunk and limbs, especially in males, to improve early detection of cutaneous melanoma and reduce the risk of metastatic disease at the time of presentation.

Thoracic metastasis of malignant melanoma of unknown primary: A case report and literature review

INTRODUCTION

Metastatic melanoma of unknown primary (MUP) is an unusual entity found in distant sites without evident skin lesion. We report a case of 45-year-old woman who underwent monobloc resection of a metastatic thoracic malignant melanoma of unknown primary, and who is currently under immunotherapy without local or distant recurrence during a follow-up of 18 months. We demonstrate through this case that R0 resection of an MUP associated with immunotherapy improves the prognosis and survival in these patients.

CASE REPORT

This is a 45-year-old woman who underwent monobloc resection of a mass carrying the anterior arch of the second left rib associated with a wedge resection of a nodule at the left upper lobe. Histology confirmed that it was a malignant melanoma. Her history was negative for melanocytic lesions, physical examination and imaging had failed to identify a primary lesion. The patient is currently under nivolumab for Stage IV melanoma and does not present any complications or recurrence during the long term follow up.

DISCUSSION

Metastatic melanoma of unknown primary (MUP) is a melanocytic lesion in distant sites in the absence of apparent skin involvement and is rare, accounting for 3, 2% of all incident melanomas as well as being yet poorly understood in terms of pathogenesis (Bae et al., 2015) [1]. MUP is clinically understudied, investigators to date have reported largely on the use of localized treatment for MUP (surgery or radiotherapy), while the efficacy of systemic therapy in MUP patients remains unexplored. Clinical trials of immunotherapy and targeted therapy in patients with advanced cutaneous melanoma have not explicitly reported response rates specific to MUP patient subgroups due to its low incidence and lack of annotation. MUP's response to these now FDA-approved therapies could add to the discussion of MUP's elusive biological characteristics, as well as aid in making clinical recommendations (Utter et al., 2017).

CONCLUSION

Metastatic MUP is an extremely rare entity which is still poorly understood, few cases are described in the literature, its treatment remains controversial and there are no specific treatment recommendations for patients with MUP. Several authors recommend local treatment when possible and tend to apply similar strategies for patients with paired stage primary known melanoma (PKM).

Biomarkers of Targeted Therapy and Immuno-Oncology in Cancers Metastatic to the Breast

The breast is a rare site for metastases, and their molecular characteristics have not been studied yet. Intrinsic molecular genetics, cancer characteristics, and breast tissue immune responses in diverse metastases to the breast have not been previously studied. We identified 64 patients with cancers metastatic to the breast: 51 carcinomas and 13 melanomas. Programmed death ligand 1 (PD-L1), steroid receptors, and HER2/neu expressions were evaluated using immunohistochemistry. Gene sequencing, copy number alterations, microsatellite instability, and tumor mutational burden were performed using next-generation sequencing platforms. The 3 most common primary sites for metastatic carcinomas were lung (37%), ovary (29%), and fallopian tubes/peritoneum (14%). TP53 mutations were commonly (50%) observed among the carcinoma cases, while other mutations were characteristic for the primary cancers (VHL in renal, BRCA1 in the fallopian tube, and BRAF in melanomas). High tumor mutational burden was detected in 5/14 carcinomas and 3/7 melanomas. Tumor cell PD-L1 expression was detected in 6 carcinomas, but not in any of the melanomas, whereas immune cells' expression of PD-L1 was seen in 17 carcinomas and 6 melanomas. Estrogen receptor status was positive in 13/49 carcinomas including 12 adenocarcinomas originating from the ovary and fallopian tube or peritoneum and 1 duodenal neuroendocrine carcinoma. No carcinoma was HER2/neu positive. Intrinsic genetic characteristics of the metastases to the breast followed the pattern commonly seen in primary tumors. Biomarkers of potential benefit to immune checkpoint inhibition therapy were limited to PD-L1-positive non-small cell lung cancer. No common characteristics of the heterogeneous group of tumor metastases to this organ were identified.

Melanoma Metastases to the Adrenal Gland Are Highly Resistant to Immune Checkpoint Inhibitors

BACKGROUND

Adrenal gland metastases (AGMs) are common in advanced-stage melanoma, occurring in up to 50% of patients. The introduction of immune checkpoint inhibitors (ICIs) has markedly altered the outcome of patients with melanoma. However, despite significant successes, anecdotal evidence has suggested that treatment responses in AGMs are significantly lower than in other metastatic sites. We sought to investigate whether having an AGM is associated with altered outcomes and whether ICI responses are dampened in the adrenal glands.

PATIENTS AND METHODS

We retrospectively compared ICI responses and overall survival (OS) in 68 patients with melanoma who were diagnosed with an AGM and a control group of 100 patients without AGMs at a single institution. Response was determined using RECIST 1.1. OS was calculated from time of ICI initiation, anti-PD-1 initiation, initial melanoma diagnosis, and stage IV disease diagnosis. Tumor-infiltrating immune cells were characterized in 9 resected AGMs using immunohistochemical analysis.

RESULTS

Response rates of AGMs were significantly lower compared with other metastatic sites in patients with AGMs (16% vs 22%) and compared with those without AGMs (55%). Patients with AGMs also had significantly lower median OS compared with those without AGMs (3.1 years vs not reached, respectively). We further observed that despite this, AGMs exhibited high levels of tumor-infiltrating immune cells.

CONCLUSIONS

In this cohort of patients with melanoma, those diagnosed with an AGM had lower ICI response rates and OS. These results suggest that tissue-specific microenvironments of AGMs present unique challenges that may require novel, adrenal gland-directed therapies or surgical resection.

Melanoma Brain Metastases in the Era of Targeted Therapy and Checkpoint Inhibitor Therapy

Simple Summary

Brain metastases are common in melanoma and are often associated with significant morbidity and mortality. Although many new treatments for melanoma have been approved in recent years, including immune checkpoint inhibitors and BRAF/MEK inhibitors, limited data are available for survival for patients with brain metastases treated with these novel therapies. The aim of this retrospective study was to evaluate current surgical, radiation, and systemic therapies over the past 10 years in melanoma patients with brain metastases. Our study noted increased overall survival in patients treated with craniotomy and CTLA-4 checkpoint inhibitors, while whole brain radiation was associated with poorer overall survival.

Abstract

Brain metastases commonly develop in melanoma and are associated with poor overall survival of about five to nine months. Fortunately, new therapies, including immune checkpoint inhibitors and BRAF/MEK inhibitors, have been developed. The aim of this study was to identify outcomes of different treatment strategies in patients with melanoma brain metastases in the era of checkpoint inhibitors. Patients with brain metastases secondary to melanoma were identified at a single institution. Univariate and multivariable analyses were performed to identify baseline and treatment factors, which correlated with progression-free and overall survival. A total of 209 patients with melanoma brain metastases were identified. The median overall survival of the cohort was 5.3 months. On multivariable analysis, the presence of non-cranial metastatic disease, poor performance status (ECOG 2–4), whole-brain radiation therapy, and older age at diagnosis of brain metastasis were associated with poorer overall survival. Craniotomy (HR 0.66, 95% CI 0.45–0.97) and treatment with a CTLA-4 checkpoint inhibitor (HR 0.55, 95% CI 0.32–0.94) were the only interventions associated with improved overall survival. Further studies with novel agents are needed to extend lifespan in patients with brain metastases in melanoma.

Multidisciplinary Care for Melanoma of Unknown Primary: Experience in the Era of Molecular Profiling

BACKGROUND

Melanoma of unknown primary (MUP) accounts for approximately 3% of melanoma diagnoses. This study sought to evaluate treatment and outcomes for a modern MUP cohort.

METHODS

A retrospective review of MUP was performed at a tertiary referral cancer center.

RESULTS

Of 815 melanoma patients, 67 (8.2%) had MUP. Men were more likely to have MUP than women (67% vs. 55%; p = 0.04). The most common sites of MUP were lymph nodes (28%), visceral solid organs (25%), brain (16%), and skin/subcutaneous tissues (10%). Of the patients who underwent tumor genomic profiling, 52% harbored pathogenic BRAF mutations. Of the 24 patients who underwent multi-gene panel testing, all had pathogenic mutations and 21 (88%) had mutations in addition to or exclusive of BRAF, including 11 patients (46%) with telomerase reverse transcriptase promoter mutations. Checkpoint inhibitors (39%) and BRAF-MEK inhibitors (7%) were the most common first-line treatments. Upfront surgical resection was used for 25% of the MUP patients, and 12 of these resections were for curative intent. During a median follow-up period of 22.1 months, the median overall survival (OS) was not met for the patients with MUP isolated to lymph nodes. At 56.8 months, 75% of these patients were alive. The median OS was 37.4 months for skin/soft tissue MUP, 33.3 months for single solid organ viscera MUP, and 29.8 months for metastatic brain MUP.

CONCLUSION

Multigene panel testing identified pathogenic mutations in all tested MUP patients and frequently identified targets outside BRAF. Despite advanced stage, aggressive multimodal therapy for MUP can be associated with 5-year OS and should be pursued for appropriate candidates.

Is Merkel Cell Carcinoma of Lymph Node Actually Metastatic Cutaneous Merkel Cell Carcinoma?

OBJECTIVES

The possibility of a so-called primary lymph node neuroendocrine carcinoma has been described in the literature. Here we evaluate cases fitting such a diagnosis and find that the cases demonstrate a convincing and pervasive pattern consistent with metastatic Merkel cell carcinoma.

METHODS

Six cases of primary lymph node Merkel cell carcinoma and one case of metastatic neuroendocrine carcinoma at a bony site, all with unknown primary, were sequenced using a combination of whole-exome and targeted panel methods. Sequencing results were analyzed for the presence of an ultraviolet (UV) mutational signature or off-target detection of Merkel cell polyomavirus (MCPyV).

RESULTS

Four of six primary lymph node cases were positive for a UV mutational signature, with the remaining two cases positive for off-target alignment of MCPyV. One case of neuroendocrine carcinoma occurring at a bony site was also positive for a UV mutational signature.

CONCLUSIONS

We find no evidence to corroborate the existence of so-called primary Merkel cell carcinoma of lymph node.

Safety, Efficacy, and Biomarker Analysis of Toripalimab in Previously Treated Advanced Melanoma: Results of the POLARIS-01 Multicenter Phase II Trial

PURPOSE

In contrast to the predominant chronic UV exposure-induced cutaneous melanoma in Caucasians, acral and mucosal comprise the majority of melanomas in Asia and respond less effectively to established treatments. The clinical application of PD-1 blockade is yet to be explored in metastatic melanoma in China.

PATIENTS AND METHODS

This phase II study was to evaluate safety and efficacy of toripalimab in advanced Chinese patients with melanoma who had failed in systemic treatments. Toripalimab was given at 3 mg/kg i.v. once every 2 weeks until disease progression or unacceptable toxicity. The primary objective was safety and objective response rate.

RESULTS

128 Patients with melanoma were enrolled, including 50 acral and 22 mucosal. As of August 15, 2019, 23 months after the last enrollment, 116 (90.6%) experienced treatment-related adverse events. ≥Grade 3 TRAEs occurred in 25 (19.5%) patients. Among 127 patients assessed, 1 complete response, 21 partial response, and 51 stable disease were observed for objective response rate of 17.3% and disease control rate of 57.5%. Median duration of response was not reached. Median progression-free survival was 3.6 months [95% confidence interval (CI) 2.7-5.3] and median overall survival was 22.2 months (95% CI, 15.3-NE). Patients with positive PD-L1 staining in tumor biopsies had significant better ORR (38.5% vs. 11.9%, P = 0.0065), PFS (7.7 months vs. 2.7 months, P = 0.013), and OS (not reached vs. 14.4 months, P = 0.0005) than PD-L1-negative patients.

CONCLUSIONS

This is the largest prospective anti-PD-1 clinical study in advanced melanoma with predominantly acral and mucosal subtypes. Toripalimab demonstrated a manageable safety profile and durable clinical response in Chinese patients with metastatic melanoma refractory to standard therapy.See related commentary by Shoushtari et al., p. 4171.

Patients with melanoma of unknown primary show better outcome under immune checkpoint inhibitor therapy than patients with known primary: preliminary results

Background: Melanoma of unknown primary (MUP) is an uncommon clinical subtype of melanoma of known primary (MKP). Objectives: We aimed to compare treatment outcomes of MUP and MKP patients who had undergone therapy with immune checkpoint inhibitors (ICPI). Methods: We studied 41 metastatic melanoma patients (32 with MKP and 9 with MUP) with an indication for ICPI. Results: Clinical characteristics such as age, gender, stage of disease, etc., did not significantly differ (P < .05) between MUP and MKP patients. 20/32 (62.5%) melanoma-specific deaths (MSD) were observed in the MKP group, whereas 2/9 (22.2%) were detected in the MUP group (P = .035). On logistic regression, the MUP status proved to be an independent predictor for a more favorable outcome under immunotherapy when compared to MKP (P = .030). Conclusion: Our preliminary results indicate that MUP patients show better clinical outcome under ICPI when compared to MKP.

Expert Elicitation to Inform a Cost-Effectiveness Analysis of Screening for Renal Cancer

BACKGROUND

Population screening for renal cell carcinoma (RCC) using ultrasound has the potential to improve survival outcomes; however, a cost-effectiveness analysis (CEA) has yet to be performed. Owing to the lack of existing evidence, we performed structured expert elicitation to derive unknown quantities to inform the CEA.

OBJECTIVE

To elicit the cancer stage distribution (proportion of individuals with each stage of cancer) for different RCC screening scenarios and the annual transition probabilities for undiagnosed disease becoming diagnosed in the National Health Service.

METHODS

The study design and reporting adhered to the Reporting Guidelines for the Use of Expert Judgement in Model-Based Economic Evaluations. The elicitation was conducted face-to-face or via telephone between each individual expert and the facilitator, aided by online material. For multinomial data, Connor-Mosimann and modified Connor-Mosimann distributions were fitted for each expert and for all experts combined using mathematical linear pooling.

RESULTS

A total of 24 clinical experts were invited, and 71% participated (7 urologists, 6 oncologists, 4 radiologists). The modified Connor-Mosimann distribution provided the best fit for most elicited quantities. Greater uncertainty was noted for the elicited transition probabilities compared with the elicited stage distributions.

CONCLUSION

We performed the first expert elicitation of RCC screening parameters, crucial information that will inform the CEA of screening. In addition, the elicited quantities may enable future health economic evaluations assessing the value of diagnostic tools and pathways in RCC.

Treatment of melanoma of unknown primary in the era of immunotherapy and targeted therapy: A Dutch population-based study

Melanoma of unknown primary (MUP) may have a different biology to melanoma of known primary, but clinical trials of novel therapies (e.g., immune checkpoint or BRAF/MEK inhibitors) have not reported the outcomes in this population. We therefore evaluated the overall survival (OS) among patients with MUP in the era of novel therapy. Data for stage III or IV MUP were extracted from a nationwide database for the period 2003–2016, with classification based on the eighth edition of the American Joint Committee on Cancer criteria. The population was divided into pre‐ (2003–2010) and post‐ (2011–2016) novel therapy eras. Also, OS in the post‐novel era was compared between patients with stage IV MUP by whether they received novel therapy. In total, 2028 of 65,110 patients (3.1%) were diagnosed with MUP. Metastatic sites were known in 1919 of 2028 patients, and most had stage IV disease (53.8%). For patients with stage III MUP, the 5‐year OS rates were 48.5% and 50.2% in the pre‐ and post‐novel eras, respectively (p = 0.948). For those with stage IV MUP, the median OS durations were unchanged in the pre‐novel era and post‐novel era when novel therapy was not used (both 4 months); however, OS improved to 11 months when novel therapy was used in the post‐novel era (p < 0.001). In conclusion, more than half of the patients with MUP are diagnosed with stage IV and the introduction of novel therapy appears to have significantly improved the OS of these patients.

What's new?

Melanoma of unknown primary (MUP) site may have a different biology to melanoma of known primary, but clinical trials of novel therapies (e.g., immune checkpoint or BRAF/MEK inhibitors) have not reported the outcomes in this population. Knowledge about outcomes could however aid clinical management of patients with MUP. In this nationwide study from 2003 to 2016, the authors show that the introduction of novel therapy has significantly improved the overall survival for patients with stage IV melanoma of unknown primary, who represented more than half of the patients diagnosed with MUP in the Netherlands.

Melanoma of unknown primary

Formally described in the 1960s, melanoma of unknown primary (MUP) is characterized by the finding of metastatic melanoma within the lymph nodes, subcutaneous tissues, and other distant sites without an evident primary lesion. The most likely hypothesis of its etiology is an immune-mediated regression of the primary after metastasis has occurred. In addition, patients with MUP appear to have equivalent or better outcomes compared with patients with known primaries of a similar stage.

Carcinoma of Unknown Primary Site (CUP) With Metastatic Renal-Cell Carcinoma (mRCC) Histologic and Immunohistochemical Characteristics (CUP-mRCC): Results From Consecutive Patients Treated With Targeted Therapy and Review of Literature

BACKGROUND

Carcinoma of unknown primary site (CUP) is a heterogenous group of metastatic cancer with no detectable primary tumor site. Diagnostic assessment occasionally presents CUP with metastatic renal-cell carcinoma (mRCC) histologic and immunohistochemical characteristics (CUP-mRCC). Efficacy and toxicity data for vascular endothelial growth factor inhibitor therapies in CUP-mRCC patients are few.

PATIENTS AND METHODS

We retrospectively reviewed consecutive patients with CUP-mRCC at a single institution between 2007 and 2018. Treatment outcomes were assessed from initiation of renal-cell carcinoma-specific therapy, including response rate, progression-free survival, and overall survival.

RESULTS

Ten patients with CUP-mRCC were identified. Median age was 64 years. Histologies were clear-cell (30%), papillary type II (20%), and unclassified renal-cell (50%) carcinoma. International Metastatic Renal Cell Carcinoma Database Consortium risk group were favorable, intermediate, and poor in 0, 40%, and 60%, respectively. One patient received empiric first-line chemotherapy. Targeted treatments were pazopanib (n = 7), sunitinib (n = 2), and sorafenib (n = 1). Objective response rate was 40%, progression-free survival was 2.5 months (95% confidence interval, 1.2-3.8), and overall survival was 5.7 months (95% confidence interval, 0-24.0). Stratified for International Metastatic Renal Cell Carcinoma Database Consortium risk, overall survival in intermediate versus poor risk group were 18.6 months and 2.3 months, respectively. Second-line therapy did not result in disease control. No new or unexpected toxicities were observed.

CONCLUSION

CUP-mRCC treated with vascular endothelial growth factor-targeted therapy is valid, feasible, and safe even though these patients had several negative prognostic factors. CUP-mRCC patients should be identified among CUP patients for specific renal-cell carcinoma therapy.