Case study 1:
A 31-year-old female (patient 10A) was initially diagnosed with stage IIIc BRAF V600E positive nodular melanoma to the skin of buttock. She was started on neoadjuvant pembrolizumab 200mg IV every 3 weeks in a clinical trial setting. After 3 cycles, she was found to have disease progression to stage IV (pT4b, N3c, M1c) with lymph node and liver metastases by the time of resection. She was then started on dabrafenib, trametinib, and pembrolizumab for four months. Pembrolizumab was intermittently held due to toxicity. She initially had a partial response but then had progression of disease in her liver, lungs, and lymph nodes. She was started on flipped dose Ipi (1 mg/kg) plus nivolumab (3 mg/kg) due to previous toxicity with pembrolizumab and tolerated 3 cycles. She had mixed response in her liver, stable disease in the lung and lymph nodes, but had progression to her bones and brain with new spine and femur lesions and two new 9 mm lesions in the left frontal and left occipital lobes. Her therapy was ultimately switched to high dose Ipi (10mg/kg) plus TMZ, and she received stereotactic radiosurgery to the brain lesions. Her subsequent scans showed decreased brain lesions and ultimately, she had complete resolution of her brain metastases and no new lesions by 3 months of treatment. After 4 cycles, she developed grade 3 hepatitis and was treated with high dose steroids with an extended period of steroid taper. While further treatment was held, she developed relapsed disease with new spinal, pulmonary, and liver lesions 5 months from the last dose of Ipi. Her lactate dehydrogenase (LDH) also peaked at this time to 2294. She was treated with standard dose Ipi (3mg/kg) plus nivolumab for 4 cycles followed by maintenance nivolumab and had another dramatic partial response (Figure 1) that is durable (no progression with 10 months of follow up now). At 17 months since high-dose Ipi was initiated, MRI brain still revealed no evidence of CNS disease. Whole body CT scan showed continued partial response except one left ovarian mass that has increased in size from 4.6cm to 5.4cm. She was taken to the operating room and underwent surgical metastatectomy of this ovarian mass. Pathology analysis revealed extensive tumor necrosis and histiocytic inflammation but no viable tumor was identified.
To further understand patient 10A’s treatment response, we analyzed molecular profiling by RNA-seq and whole-exome sequencing (WES) of the tumors harvested throughout her treatment, including the surgical specimen at the initial site of diagnosis (P1, harvested from skin of the buttock) and subsequent site of metastasis to the liver (M2) 2 days after first dose of low dose Ipi plus nivolumab and prior to the Ipi10 plus TMZ treatment, and to the subcutaneous soft tissue in the back (M3) after disease progression to Ipi10 plus TMZ and prior to subsequent Ipi 3 plus nivolumab (Figure 1A and 2A). WES revealed only 12 shared somatic mutations among these tumors (Figure 2B), including the BRAF V600E mutation, and other genes important in defining melanoma and continued activation of the MAPK pathway. Calculations of tumor mutational burden (TMB) indicates the liver metastasis (M2) has higher TMB 7.5 mutations/Mb than the primary tumor (P1) with 1.4 mutations/Mb and the later soft tissue metastasis (M3) with 2.7 mutations/Mb. We focused on the genes mutated in the immune- and inflammation-related pathways from the Hallmark gene sets, and found that the interferon alpha and gamma response pathways were enriched in the genes exclusively mutated in the M2 sample (Figure 2C). Interestingly, IFNGR2 is exclusively mutated in M3, which may play a role in altering the response to immunotherapy. To better understand the transcriptome changes during treatment, single sample gene set enrichment analysis (ssGSEA) was performed on the RNA-seq of these tumors. ssGSEA of the liver metastasis (M2) showed an enrichment of immune-related gene sets including interferon alpha and gamma responses (Figure 2D). M3, when compared to P1, is also enriched with the inflammatory response gene set. On the other hand, pathways shown to be negative regulators of anti-tumor immune response, such as Wnt signaling and TGF beta signaling, are down regulated in both M2 and M3. RNA-Seq also revealed upregulation of alternative signaling pathways such as PI3K/AKT, Notch and Hedgehog signaling in M3 when compared to P1.
Case study 2:
A 52 year old male (patient 10B) also responded to high dose Ipi plus TMZ after progressing on multiple lines of therapy. At age 45 he was initially diagnosed with stage IIIC (pT3bN3M0) superficial spreading melanoma to the right forehead. He underwent surgical resection and sentinel lymph node biopsy, as well as right parotidectomy (due to positive sentinel lymph node involvement) and participated in an adjuvant vaccine trial. Three years later he developed a single lung metastasis to the left lower lobe. He underwent wedge resection of lung where this lesion is involved and was started on adjuvant nivolumab. After 5 months of treatment (doses were intermittently held due to toxicity), he developed metastases to the left sided pleura. Next generation sequencing revealed a BRAF V600E mutation, so triple therapy with dabrafenib, trametinib plus pembrolizumab was started. He initially had a partial response to this regimen but 16 months later his melanoma progressed and metastasized to the brain. This was initially managed by SRS to the brain lesion and continued triple therapy, but systemic disease eventually progressed by 7 months. He started Ipi (initially 1mg/kg but increased to 3mg/kg cycles 2-4) plus nivolumab and tolerated all 4 cycles of combination and 2 more doses of monotherapy nivolumab. However, his disease continued to worsen in his CNS with 3 new lesions, and he was started on encorafenib and binimetinib. His disease initially stabilized then progressed both systemically and in the CNS within 10 months. High dose Ipi (10 mg/kg) plus TMZ were started. After 3 cycles, his PET CT revealed partial response and near complete resolution of FDG activity of his disease burden (Figure 3).
Cohort:
Due to the dramatic response to high dose Ipi plus TMZ in the cases detailed above, we were interested in analyzing the outcomes of other patients with advanced melanoma treated with this combination at our institution. Of the 12 patients with advanced melanoma treated with Ipi plus TMZ, six were treated with high dose Ipi (10 mg/kg), and six were treated with standard dose Ipi (3 mg/kg) (Table 1). Age and BRAF mutations were similar between both groups. All but one patient was previously treated with Ipi. Notable differences between groups include prior exposure to Ipi plus nivolumab. All patients treated with high dose Ipi had prior treatment with Ipi plus nivolumab, whereas only half of patients treated with standard dose Ipi did (Table 1).
Table 1: Baseline characteristics and outcomes of patients treated with Ipi 10 mg/kg + TMZ (orange) and Ipi 3 mg/kg + TMZ (blue).
This is a very heavily pre-treated patient population with most patients only receiving one dose before moving on to hospice or passing away from disease progression (patients 10E, 10F, 3C, 3D, 3E, 3F). All patients treated with regular dose Ipi plus TMZ had progression of disease as their best response, while two patients treated with high dose Ipi plus TMZ had partial response at the first response evaluation (described in the case section), and a third patient who had a mixed response.
At a median follow up of 119 days, patients treated with high dose Ipi plus TMZ had statistically significant longer median progression-free survival (PFS) of 144.5 days (27 – 219) vs 44 days (26 – 75) for standard dose Ipi and TMZ, p=0.04 (Figure 4). Due to the small sample size in each cohort and heterogeneous prior treatment history, no statistically significant differences can be drawn from subgroup analysis; however, there is also a similar trend of longer median PFS for patients who had more than 1 cycle of treatment, 144.5 days (96 – 219) for high dose Ipi plus TMZ vs 61 days (47 – 75) for standard dose Ipi plus TMZ, and in patients who were previously exposed to regular dose Ipi plus nivolumab, 144.5 days (27 – 219) vs 39 days (26 – 55), respectively (Figure 4). There is no statistical difference in terms of median overall survival (OS) but a trend of longer median OS of 154.5 days (27 – 537 days) vs 89.5 days (26 – 548 days) for high and standard dose Ipi plus TMZ. This trend is more evident in patients who were previously exposed to regular dose Ipi plus nivolumab; median OS in the high dose Ipi group was 154.5 days (27 – 537) vs 39 days (26 – 55) of the standard dose Ipi group (Figure 4).