Melanoma

Primary giant aggressive amelanotic duodenal melanoma

Primary malignant melanoma of the gastrointestinal tract is extremely rare. A 35-year-old man presented with complaints of abdominal pain and weight loss. Contrast enhanced computed tomography showed a large mass involving the duodenum and the superior mesenteric vessels. Upper gastrointestinal endoscopy demonstrated a large, friable mass along the duodenal wall and biopsy was suggestive of malignant melanoma. A detailed physical examination and whole body imaging (positron emission tomography and computed tomography) did not reveal any other lesion. The patient underwent a pancreaticoduodenectomy with segmental resection and anastomosis of the superior mesenteric vein as well as a segmental colectomy. His postoperative recovery was uneventful. The histopathology of the operative specimen showed a malignant amelanotic melanoma arising from the duodenum with lymph nodal involvement. He received oral temozolomide. However, he developed liver metastasis at six months and again at ten months, which was managed with radiofrequency ablation both times. He is doing well at 32 months of follow-up review. Multimodality treatment including surgery, adjuvant chemotherapy and salvage therapy appears to be a promising tool for achieving long-term survival in such patients.

Melanoma and pregnancy

Melanoma is the most common cancer in women during their reproductive years and kills more young Australians than any other single cancer. Care of women whose pregnancy is complicated by a diagnosis of malignancy is complex. The risk of delaying treatment to the mother, the short-term and long-term risks of premature delivery to the child, and the immediate risks to the foetus and long-term risks to the child of maternal treatment with surgery, radiotherapy or medical therapies must be considered.

FDG PET scans as evaluation of clinical response to dendritic cell vaccination in patients with malignant melanoma

BACKGROUND

Measurements of tumour metabolism by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) have been successfully applied to monitor tumour response after chemo- and chemo-radiotherapy and may not have the same limitations as other morphological imaging techniques. In this study it is investigated whether FDG-PET might add information on the efficacy of immune therapy.

MATERIALS AND METHODS

In a retrospective analysis data from patients with advanced progressive melanoma, treated with DC vaccinations and evaluated by PET/CT scans at baseline as well as after 6 vaccinations were analysed. If a patient achieved stable disease according to RECIST, additional vaccinations were given. The PET scans were evaluated according to EORTC guidelines.

RESULTS

PET/CT scans from 13 patients were evaluated. According to RECIST 3 patients achieved stable disease and 10 patients progressed. Interestingly, when evaluated by PET scans 2 patients had partial metabolic response and 1 patient had complete metabolic response of the 2 index lesions even though a new lesion appeared simultaneously. Ten patients were seen to have stable or progressive metabolic disease.

CONCLUSION

By adding PET scans to the CT evaluation of patients treated with DC vaccines, a more detailed picture of the single lesions was found. This seems to improve the clinical evaluation of the treatment. The lack of correlation between the PET and CT scans suggests that some of the increases in target lesions seen in CT scans might be due to oedema or immune-infiltrates and not progression of the disease. Thus, further investigation into the contribution of PET scans to the evaluation of cancer immunotherapy is needed.

FDG-PET is a good biomarker of both early response and acquired resistance in BRAFV600 mutant melanomas treated with vemurafenib and the MEK inhibitor GDC-0973

Background

The BRAF inhibitor, vemurafenib, has recently been approved for the treatment of metastatic melanoma in patients harboring BRAF^V600 mutations. Currently, dual BRAF and MEK inhibition are ongoing in clinical trials with the goal of overcoming the acquired resistance that has unfortunately developed in some vemurafenib patients. FDG-PET measures of metabolic activity are increasingly employed as a pharmacodynamic biomarker for guiding single-agent or combination therapies by gauging initial drug response and monitoring disease progression. However, since tumors are inherently heterogeneous, investigating the effects of BRAF and MEK inhibition on FDG uptake in a panel of different melanomas could help interpret imaging outcomes.

Methods

¹⁸ F-FDG uptake was measured in vitro in cells with wild-type and mutant (V600) BRAF, and in melanoma cells with an acquired resistance to vemurafenib. We treated the cells with vemurafenib alone or in combination with MEK inhibitor GDC-0973. PET imaging was used in mice to measure FDG uptake in A375 melanoma xenografts and in A375 R1, a vemurafenib-resistant derivative. Histological and biochemical studies of glucose transporters, the MAPK and glycolytic pathways were also undertaken.

Results

We demonstrate that vemurafenib is equally effective at reducing FDG uptake in cell lines harboring either heterozygous or homozygous BRAF^V600 but ineffective in cells with acquired resistance or having WT BRAF status. However, combination with GDC-0973 results in a highly significant increase of efficacy and inhibition of FDG uptake across all twenty lines. Drug-induced changes in FDG uptake were associated with altered levels of membrane GLUT-1, and cell lines harboring RAS mutations displayed enhanced FDG uptake upon exposure to vemurafenib. Interestingly, we found that vemurafenib treatment in mice bearing drug-resistant A375 xenografts also induced increased FDG tumor uptake, accompanied by increases in Hif-1α, Sp1 and Ksr protein levels. Vemurafenib and GDC-0973 combination efficacy was associated with decreased levels of hexokinase II, c-RAF, Ksr and p-MEK protein.

Conclusions

We have demonstrated that ¹⁸ F-FDG-PET imaging reflects vemurafenib and GDC-0973 action across a wide range of metastatic melanomas. A delayed post-treatment increase in tumor FDG uptake should be considered carefully as it may well be an indication of acquired drug resistance.

Trial registration

ClinicalTrials.gov NCT01271803