UNASSIGNED: To report an atypical presentation of severe toxicity, anterior chamber (AC) inflammation, and transient parafoveal formation of subretinal fluid induced by the subconjunctival injection of 5-fluorouracil (5-FU).
UNASSIGNED: Case presentation.
UNASSIGNED: Seven weeks after trabeculectomy, a 40-year-old white male had a subconjunctival injection of 5-FU. Within minutes after the injection, the lens turned grey and then total white. Initially, AC was clear, and 20 min later, a severe AC reaction was detected. The patient was prescribed hourly dexamethasone eye drops and tropicamide eye drops twice daily. Two days post-injection, vision improved, AC reaction was minimal, and there was whitish fibrinous material on the anterior surface of the lens, extending up to the pupillary margin. Minimal posterior synechiae were observed, and upon dilation, the remainder of the anterior surface of the lens appeared completely clear, indicating that only the portion of the lens not covered by the iris exhibited fibrinous material and deposits. One week post-injection, vision worsened due to severe corneal toxicity. The dimensions of the whitish fibrinous material on the anterior lens capsule decreased, and macular scans revealed parafoveal subretinal fluid. Two weeks later, vision significantly improved, and the dimensions of the whitish fibrinous material on the anterior lens capsule were further decreased. The subretinal fluid had completely resolved.
UNASSIGNED: We describe a rare case of severe toxicity, AC inflammation, and transient parafoveal subretinal fluid formation caused by the 5-FU. This was treated with topical steroid treatment, and eventually some level of lens opacification persisted despite significant clearance of the AC inflammation.

Toxic leukoencephalopathy (TL) refers to damage to the brain white matter following exposure to toxic agents. Multiple agents are incriminated in this condition, including chemotherapy drugs. 5-Fluorouracil, widely used in oncology, is responsible for neurotoxicity in less than 5% of cases. We report the case of a 54-year-old male patient who presented with neurological symptoms following 5-FU-based chemotherapy for gastric adenocarcinoma, and whose MRI scan revealed signs suggestive of toxic leukoencephalopathy. We also report on the evolution of the abnormalities described on his MRI after 1 year.

Continuous low-dose 5-FU was popularized as a therapy for pretreated metastatic breast cancer for the past few decades, spurred by the advent of the electronic infusion pump. Capecitabine, otherwise known by its trade name Xeloda, is a prodrug of 5-fluorouracil (5-FU), which is administered orally in many chemotherapy regimens, and plays a role in metastatic breast cancer treatment refractory to traditional anthracyclines and taxane therapy. In this case presentation, we describe a unique case of refractory de-novo stage IV triple-negative breast cancer presented with right breast primary invasive ductal carcinoma, extensive lymphadenopathy, with biopsy proven bone marrow infiltration, diffuse hepatomegaly, splenomegaly, significant hyperbilirubinemia, and bone marrow failure treated with continuous 5-FU infusion and subsequently oral capecitabine after initial treatment failure with nab-paclitaxel and sacituzimab govitecan. With this case presentation, the authors aim to showcase the versatility of 5-FU and its prodrug in treatment of metastatic triple-negative breast cancer with severe bone marrow and liver involvement while highlighting key physiologic and pharmacologic mechanisms.

The odontogenic keratocyst (OKC) is known for its high recurrence rate and disputed treatment modalities. In this report, we review the literature elucidating the efficacy of 5-fluorouracil (5-FU) topical application for recurrent OKC, and discuss the management of an OKC with 5-FU after enucleation and a 12-month follow-up. A 38-year-old female patient with an aggressive OKC in the right mandible underwent surgical curettage followed by topical application of 5-FU. Regular follow-up examinations for 12 months (radiological evaluation at three, six, and 12-month intervals) showed no signs of recurrence, with complete resolution of the cystic lesion and gradual bone regeneration. New bone formation was identified in the radiographic follow-up.  This case demonstrates the potential efficacy of topical 5-FU as a promising treatment modality for OKC, warranting further research and validation. A novel and successful therapy for OKC is the topical application of 5-FU. After enucleation, topical application of 5-FU efficiently treats OKC, leading to normal bone healing and regeneration without any adverse local or systemic effects.

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BACKGROUND: Fluorouracil-induced leukoencephalopathy is a rare complication and has been reported to present as confusion, oculomotor abnormality, ataxia, and parkinsonism; however, there is no previous report of a presentation mimicking neuroleptic malignant syndrome. Acute cerebellar syndrome may occur, which can be explained by the extremely high accumulation of the drug in the cerebellum. However, presentation mimicking neuroleptic malignant syndrome similar to our case has never been reported.
METHODS: Here, we describe a 68-year-old Thai male presenting with advanced-stage cecal adenocarcinoma, as well as symptoms and signs indicative of neuroleptic malignant syndrome. He received two doses of intravenous metoclopramide 10 mg 6 hours before his symptoms occurred. Magnetic resonance imaging scan revealed signal hyperintensity within the bilateral white matter. Further evaluation showed that his thiamine level was extremely low. Thus, he was diagnosed with fluorouracil-induced leukoencephalopathy mimicking neuroleptic malignant syndrome. The concomitant fluorouracil-induced thiamine deficiency eventually leads to rapid depletion of thiamine and was considered a risk factor for fluorouracil-induced leukoencephalopathy.
CONCLUSIONS: Fluorouracil-induced leukoencephalopathy is believed to be caused by insult causing mitochondrial dysfunction. However, the exact mechanism remains unknown, but our finding suggests that thiamine deficiency plays a crucial role in fluorouracil-induced leukoencephalopathy. Diagnosis is usually delayed due to a lack of clinical suspicion and results in significant morbidity requiring unnecessary investigations.

UNASSIGNED: More than half of patients with colorectal cancer (CRC) present with metastatic disease or develop recurrent disease on first-line and second-line options. Treatment beyond the second line remains an area of unmet need for patients with progressive or recurrent disease.
UNASSIGNED: We retrospectively reviewed data of adult (>18 years old) patients with mCRC who received regorafenib + 5FU combination therapy at Houston Methodist Hospital with outcomes of interest including response rate, discontinuation due to side effects, and overall survival.
UNASSIGNED: Seven patients received regorafenib + 5FU combination therapy for mCRC after receiving at least two other lines of therapy (including at least one fluorouracil-based therapy). Four patients (57%) achieved disease control in 7-12 weeks after therapy initiation while three patients developed recurrent disease. In patients who achieved disease control, no new adverse events were reported among patients with this combination.
UNASSIGNED: Regorafenib and Fluorouracil combination could be considered an option beyond the second line for patients with treatment-refractory metastatic colorectal cancer. Further studies, including a prospective trial, are needed to investigate the efficacy and safety of regorafenib plus 5FU therapy compared to other limited available therapies.

BACKGROUND: The administration of 5-fluorouracil (5FU) in the treatment of gastrointestinal (GI) malignancies is associated with common side effects such as mucositis, diarrhoea, and myelosuppression, which are easily managed with supportive measures and dose adjustments. Cardiotoxicity and neurotoxicity are rare but reversible side effects of 5-FU and are treated with withdrawal of the drug and conservative measures. The presenting symptoms of 5-FU-induced leukoencephalopathy are often confusing and pose a diagnostic dilemma in routine clinical practice.
METHODS: We report a series of five patients with GI malignancies who developed 5-FU-induced leukoencephalopathy.
RESULTS: All (n = 5) had Naranjo scores of 6-7, predictive of 5-FU-related adverse effects, with clinical and radiological findings suggestive of 5-FU-induced encephalopathy as described in prior literature. The median time to onset of symptoms from initiation of 5FU was 3 days (range: 2-4 days). All patients improved after conservative management with complete neurological recovery.
CONCLUSIONS: Prompt recognition of this rare yet severe adverse effect of 5-FU-based chemotherapy aids early withdrawal of the offending agent (5-FU) and timely initiation of supportive measures and helps plan alternative oncological interventions.

Capecitabine is an oral 5-fluorouracil prodrug with antimetabolite activity commonly used in advanced colorectal and breast cancer. It presents with a generally good toxicity profile and most of the adverse events can be managed effectively. Enterocolitis is a rare, under-reported, but potentially fatal adverse event associated with capecitabine use. To the best of our knowledge, there are 21 cases of capecitabine-related enterocolitis reported in the literature. We herein present a narrative literature review of enteritis/colitis cases associated with capecitabine use, with highlight to the most common clinical presentation, common imaging and microscopic findings and management approach. We furthermore present a case of severe capecitabine-related enteritis.

Cutaneous metastasis from colon cancer is rare, occurs in less than 6% of patients and its associated with poor prognosis. Most often it presents in the abdomen, inguinal or perineal regions, supraclavicular area, and less commonly on the face, neck, scalp, and prior surgical sites. We present a case of a 41-year-old female with colon cancer who developed cutaneous metastases to the scalp, and was treated with topical 5-FU and radiation therapy. Treatment options for cutaneous metastases usually include systemic therapy, topical chemotherapy, surgical excision, or radiation. Our case is probably the first report who was treated with topical 5-FU in addition to radiation therapy. This treatment modality is easy to use and we would recommend clinical trials to be conducted to further study the use of topical 5-FU.