Catherine A.B. Saunders

Antiproliferative Effects of Continued Mitogen-Activated Protein Kinase Pathway Inhibition following Acquired Resistance to BRAF and/or MEK Inhibition in Melanoma

Inhibitors of the mitogen-activated protein kinases (MAPK), BRAF, and MAP–ERK kinase (MEK) induce tumor regression in the majority of patients with BRAF-mutant metastatic melanoma. The clinical benefit of MAPK inhibitors is restricted by the development of acquired resistance with half of those who benefit having progressed by 6 to 7 months and long-term responders uncommon. There remains no agreed treatment strategy on disease progression in these patients. Without published evidence, fears of accelerated disease progression on inhibitor withdrawal have led to the continuation of drugs beyond formal disease progression. We now show that treatment with MAPK inhibitors beyond disease progression can provide significant clinical benefit, and the withdrawal of these inhibitors led to a marked increase in the rate of disease progression in two patients. We also show that MAPK inhibitors retain partial activity in acquired resistant melanoma by examining drug-resistant clones generated to dabrafenib, trametinib, or the combination of these drugs. All resistant sublines displayed a markedly slower rate of proliferation when exposed to MAPK inhibitors, and this coincided with a reduction in MAPK signaling, decrease in bromodeoxyuridine incorporation, and S-phase inhibition. This cytostatic effect was also associated with diminished levels of cyclin D1 and p-pRb. Two short-term melanoma cultures generated from resistant tumor biopsies also responded to MAPK inhibition, with comparable inhibitory changes in proliferation and MAPK signaling. These data provide a rationale for the continuation of BRAF and MEK inhibitors after disease progression and support the development of clinical trials to examine this strategy. Mol Cancer Ther; 12(7); 1332–42. ©2013 AACR.

18F-labelled fluorodeoxyglucose–positron emission tomography (FDG–PET) heterogeneity of response is prognostic in dabrafenib treated BRAF mutant metastatic melanoma

BACKGROUND Little is known about the prevalence and clinical significance of heterogeneity of positron emission tomography with (18)F-labelled fluorodeoxyglucose-positron emission tomography (FDG-PET) response. We aim to determine the prevalence, and clinicopathologic correlates of intra-patient heterogeneity of FDG-PET response in metastatic melanoma treated with dabrafenib, and to determine whether heterogeneity predicts clinical outcome. METHODS Patients with BRAF mutant metastatic melanoma and ≥ 2 FDG avid lesions treated on the Phase I trial of dabrafenib at a single institution (n=23) were included. FDG-PET response was assessed by comparing baseline PET scans with scans at day 15. A heterogeneous response was defined as responding and new or metabolically progressing lesion(s) in a patient, or >10% of lesions with a stable metabolic response and responding lesions in a patient. RESULTS Six (26%) patients had a heterogeneous PET response. The median time to progression (TTP) was 7.4 months (95% confidence interval (CI): 6.5-8.3) for PET homogeneous responders and 3.0 months (95%CI: 0.6-5.4) for PET heterogeneous responders. There were no homogeneous non-responders. Age, BRAF mutation genotype, dose, and lactate dehydrogenase, did not predict for heterogeneity of PET response. Heterogeneity did not correlate with tumour response. Lung metastases were more likely to respond than other visceral metastatic sites. CONCLUSIONS Heterogeneous FDG-PET responses are common in metastatic melanoma treated with dabrafenib, and heterogeneity is associated with a shorter TTP. FDG-PET heterogeneity may predict molecular heterogeneity, and FDG-PET directed biopsies may facilitate investigation into mechanisms of resistance to signal pathway inhibitors.

Residual FDG‐PET metabolic activity in metastatic melanoma patients with prolonged response to anti‐PD‐1 therapy

18‐Fluorodeoxyglucose positron emission tomography (FDG‐PET) scans were performed on 27 patients with unresectable stage IIIC or IV melanoma after prolonged treatment with anti‐PD‐1 antibodies to examine the hypothesis that patients with prolonged response to treatment may have metabolically inactive lesions by FDG‐PET. Scans were performed at a median of 15.2 months (range 12–29 months) after starting treatment. Overall, 15 of 27 (56%) patients had a positive FDG‐PET scan. Eight patients with positive scans underwent biopsy; 5 of 8 (62%) were melanoma and 3 of 8 (38%) were immune cell infiltrates. Of the 12 patients with negative FDG‐PET scans, six had residual computerized tomography‐visible lesions, five have ceased treatment, and none have recurred with follow‐up of 6–10 months. Patients with residual metastases after a prolonged period without progression on anti‐PD‐1 therapy may have metabolically inactive lesions. Isolated metabolically active lesions in clinically well patients may reveal immune cell infiltrates rather than melanoma.

The incidence of left iliac fossa uptake of 99mTc-DTPA in renal scanning

In rare cases, extrarenal uptake of technetium-99m diethylenetriamine penta-acetic acid (99mTc-DTPA) has been reported, e.g. in tumours or abscesses. Although in our experience a relatively common occurrence, increased uptake in the left iliac fossa (LIF) and its incidence have not been described. This retrospective study set out to establish the incidence of this phenomenon and to exclude malignancy as the cause. All patients who had a renal 99mTc-DTPA scan between 1 January 1996 and 31 December 1997 had their scans reviewed. Presence and grade of increase in iliac fossa activity were determined by consensus agreement of three observers. The list of patients with increased uptake was cross-referenced against the New South Wales (Australia) Cancer Council database to exclude the possibility of a neoplastic lesion in this region. Increased LIF uptake was noted in 41 of the 231 (18%) consecutive patients (18 men, 23 women; mean age 43 years, range 20–83). Among these 41 patients, uptake was severe in 2 (5%), moderate in 12 (29%) and mild in 27 (66%). No patient had increased uptake in the right iliac fossa. Only one patient had a malignant lesion but this was excluded as being the cause of LIF uptake. No other patient developed malignancy (mean follow-up time 4.1 years; range 3.2–5.1). Increase in LIF uptake is a common, benign finding most likely due to activity within the descending colon. It occurs in approximately 18% of the population, and it is important to recognise such uptake in order to avoid misdiagnoses.

Abstract A25: BRAFV600E mutations in serous ovarian cancer and response to the BRAF inhibitor, dabrafenib.

Low-grade serous ovarian cancer (LGSC) is a challenging disease to treat effectively. It often occurs in young women and it is well-recognized to be resistant to standard chemotherapy. The underlying molecular driver mutations are now beginning to be understood and they are distinctly different from the more common counterpart, high-grade serous ovarian cancer. LGSC are characterized by somatic mutations in RAS/RAF genes and a number of new agents have been developed that target these mutations, and related activated pathways. However, it is not yet known which pathway-targeted drugs, or combination of drugs, will be effective in the treatment of LGSC. BRAF V600E mutations have been reported in LGSC and BRAF inhibitors have demonstrated significant improvement in progression-free survival in patients with BRAF-mutant melanoma. However, limited response is seen in other cancer types, such as colorectal cancers harboring the same mutation, suggesting that clinical benefit is tumor-type specific. In this study we aimed to characterize BRAF mutations in LGSC and to determine whether BRAF inhibitors could demonstrate a clinical benefit in ovarian cancer patients. Patients with LGSC were identified through the Australian Ovarian Cancer Study and the Westmead GynBiobank, Sydney, Australia. Tumor mutations were assessed using targeted and exome sequencing, and gene copy number was measured by whole genome SNP arrays. Tumor expression of BRAF V600E protein was also assessed by immunohistochemistry. Dabrafenib monotherapy was trialed in a patient with a somatic BRAF V600E mutation and progress was monitored clinically, biochemically using CA125 tumor marker levels and radiologically with PET imaging. Amongst Grade 1 serous ovarian carcinoma cases, 5/40 (12.5%) were shown to have a BRAF V600E mutation. Tumors with a BRAF V600E mutation had a relatively low degree of gene copy number change and were TP53 wild-type. The BRAF-inhibitor, dabrafenib was trialed in a heavily pre-treated BRAF V600E mutation-positive LGSC patient with progressive chemotherapy-resistant disease (n=1). Whole exome sequencing confirmed the BRAF V600E mutation was the highest frequency variant allele present and also identified deleterious mutations in other cancer-associated genes including CSMD1 , BMP1 and DNM1 at lower frequencies, suggestive of sub-clonal events. The patient received dabrafenib monotherapy for 11 months, and demonstrated a substantial clinical, radiological and biochemical response, with complete normalization of her CA125 levels for the first time in six years. These results demonstrate that molecular analysis of low-grade serous ovarian carcinoma can identify targetable mutations and provide effective treatment options. The substantial response to dabrafenib suggests that BRAF inhibition represents a potential therapeutic option for ovarian cancer patients with somatic BRAF V600E mutations and should be tested in future trials. However, the results also highlight the need for novel clinical trial design, as traditional clinical trials are unlikely to be effective in such rare ovarian cancer sub-groups. Citation Format: Anna DeFazio, Tania Moujaber, Dariush Etemadmoghadam, Catherine Kennedy, Yoke-Eng Chiew, Rosemary L. Balleine, Catherine Saunders, Gerard V. Wain, Alexander Dobrovic, Australian Ovarian Cancer Study Group (AOCS), David DL Bowtell, Paul R. Harnett. BRAFV600E mutations in serous ovarian cancer and response to the BRAF inhibitor, dabrafenib. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A25.

BRAF Mutations in Low-Grade Serous Ovarian Cancer and Response to BRAF Inhibition

PurposeLow-grade serous ovarian carcinoma (LGSC) responds poorly to chemotherapy and is characterized by activating mutations in the Ras sarcoma–mitogen-activated protein kinase (RAS-MAPK) pathway, including oncogenic BRAF. However, response to BRAF inhibitors is tumor-type specific. Significant improvement in survival is seen in patients with BRAF-mutant melanoma, but other cancer types, such as colorectal cancers, are generally less sensitive. We examined the frequency and characteristics of BRAF-mutated LGSC and described the response to treatment with BRAF inhibitors.Patients and MethodsMutations were assessed in LGSC (N = 65) by using targeted, exome, and whole-genome sequencing. Patient characteristics, treatment, and clinical outcome were assessed, and the median follow-up time was more than 5 years. BRAF inhibitors were trialed in two patients with a somatic BRAF V600E mutation: one patient received dabrafenib monotherapy and was monitored clinically, biochemically (cancer antigen [CA]-125 levels)...

Assessment of Pediatric Hydronephrosis Using Output Efficiency

UNLABELLED Diagnosing obstruction in pediatric patients with hydronephrosis, and renal impairment is often difficult. Renal output efficiency (OE) is a parameter that may improve diagnostic accuracy by allowing normalization of washout according to renal function. The aims of this study were to define a normal range for OE in infants and children and to evaluate its diagnostic accuracy in cases with hydronephrosis. METHODS Seventy-four children (91 hydronephrotic kidneys; median age, 4 mo; 22 girls and 52 boys) underwent 99mTc-labeled mercaptoacetyl-triglycine scintigraphy using intravenous volume expansion (15 ml/kg normal saline), furosemide diuresis and urethral catheterization, if vesicoureteric reflux was present. Images were interpreted by consensus of two or more experienced observers using visual assessment of the images, differential function and clearance half-time after furosemide (T(1/2)), as well as OE. The final diagnosis was based on surgical findings (n = 23 kidneys) or follow-up for >12 mo (n = 68). RESULTS Final diagnosis in 22 of the 91 hydronephrotic kidneys was obstruction at the pelviureteric (n = 21) or vesicoureteric (n = 1) junction and no obstruction in the remaining 69. The overall diagnostic accuracy of OE was 89%. Using exhaustive search multivariate logistic regression analysis, only reduced OE (p < 0.001) and decreased renal uptake by visual assessment (p = 0.058) were independently predictive of obstruction (R2 = 0.726). In dilated but unobstructed kidneys, mean OE was 93% +/- 7.1%. In the normal kidneys, mean OE was 96% +/- 3.1%. CONCLUSION OE improves the diagnostic accuracy of diuretic renography in children and neonates with hydronephrosis and suspected obstruction. Output efficiency should exceed 89% in normal kidneys and 79% in unobstructed, hydronephrotic kidneys.