Plasma ctDNA Monitoring of a PTCH1-Mutant Metastatic Adult Medulloblastoma Showing a Durable Benefit With Vismodegib.

Adult medulloblastoma (MB) is a rare disease affecting 0.6 persons per million adults over 19 years of age. The SHH-activated/TP53-wild type is the most common subtype, accounting for 60% of adult MBs, being characterized by mutations in PTCH1, SMO, or the TERT promoter. Several small studies demonstrate objective but short-lived responses to SMO inhibitors such as vismodegib or sonidegib. Like other oncogene-addicted solid tumors, detection of the corresponding drivers through liquid biopsy could aid in the molecular diagnosis and monitoring of the disease through less invasive procedures. However, most studies have only evaluated cerebrospinal fluid as the ctDNA reservoir, and very limited evidence exists on the role of liquid biopsy in plasma in patients with primary central nervous system tumors, including MB. We present the case of a 26-year-old patient with a recurrent MB, in which next-generation sequencing (FoundationOne CDx) revealed a mutation in PTCH1, allowing the patient to be treated with vismodegib in second line, resulting in a durable benefit lasting for 1 year. Using an in-house digital PCR probe, the PTCH1 mutation could be tracked in ctDNA during treatment with first-line chemotherapy and while on treatment with vismodegib, demonstrating a precise correlation with the radiological and clinical behavior of the disease.

Hyper-late major response after 5†years of nivolumab: role of treatment beyond progression in head and neck cancer.

Patients with recurrent/metastatic (R/M) platinum-refractory squamous cell carcinoma of the head and neck (SCCHN) have fewer treatment options and harbor an especially poor prognosis. Maintaining treatment with anti-PD1 agents beyond response evaluation criteria in solid tumors-defined disease progression (TBP) has been shown to be efficacious in several solid tumors, including head and neck cancer. We present the case of a platinum-refractory locally recurrent, PD-L1-negative hypopharyngeal carcinoma, that received second-line nivolumab which was then maintained beyond progression under the following criteria: no Eastern Cooperative Oncology Group performance status deterioration, no rapidly progressive disease, no severe toxicity, and evidence of overall treatment benefit. The patient achieved a partial response 8 months after starting second-line nivolumab, with progressive disease at 26 months, then followed by the first TBP with nivolumab lasting for 15 months due to a new tumor progression. A second TBP with nivolumab lasting for 7 months, was followed by a third TBP with nivolumab for 12 months and achieving a major tumor response. Treatment is still ongoing 60 months after starting nivolumab, with excellent tolerance to therapy. Maintaining anti-PD1 agents beyond progression is an efficacious treatment option for patients with R/M SCCHN, that may achieve very durable disease control and even late major responses.

Profound ctDNA and radiological responses after 2 cycles of avelumab in a metastatic Merkel cell carcinoma of the head and neck.

BACKGROUND: Merkel cell carcinoma (MCC) is an uncommon skin cancer that in more than 90 % of cases develops within the head and neck region. MCC is an aggressive disease with a dismal prognosis before the advent of immunotherapy. Avelumab, an anti-PDL1 agent is approved since 2017 for the treatment of advanced MCC after demonstrating a high response rate and favorable impact in survival. METHODS: Next generation sequencing (NGS) of the primary tumor biopsy from initial diagnosis (Foundation One CDx, Roche Diagnostics) as well as from plasma samples (Foundation One Liquid, Roche Diagnostics) obtained before and during treatment with avelumab were performed. RESULTS: We present the case of a patient with a metastatic MCC developing in the left parotid gland / pre-auricular area in an 80-year-old male with a long-lasting history of high UV exposure. After two cycles of avelumab 10 mg/kg/q2wk a near complete metabolic response and a major radiological response occurred in parallel to a brisk reduction in the ctDNA tumor fraction as well as variant-allele frequencies (VAFs) of all the mutations detected before the start of avelumab. CONCLUSION: Avelumab may achieve rapid and major responses in metastatic MCC. Our study demonstrates that ctDNA mirrors radiological responses and may serve as an ideal companion for diagnosis and disease monitoring in MCC.

Major and durable responses to photon and electron-beam palliative radiotherapies after immune-checkpoint inhibitors in head and neck cancer.

BACKGROUND: The immuno-modulatory effects of ionizing radiation are well-known and preclinical studies suggest a synergistic effect of combining radiotherapy (RT) and IO. However, data regarding the clinical activity and safety of this approach are limited. METHODS: We present the cases of two patients with SCCHN primary progressing to PDL1-based IO within a clinical trial (NCT03383094), that received subsequent but not concurrent palliative RT using two different modalities (electron beam and photon beam therapies). RESULTS: Both patients achieved major and durable responses at 4 irradiated sites, with excellent tolerance and no grade ≥ 3 toxicities. Complete response occurred in 3 of the disease areas (all locoregional) and partial response in 1 metastatic lesion. CONCLUSION: Palliative radiotherapy after progression to IO was safe and demonstrated profound and durable responses in the cases presented.