Patients with advanced cancer present various symptoms as their disease progresses. Among these, fatigue is a frequent symptom in patients with advanced cancer and is associated with decreased quality of life (QOL). However, there are few reports regarding its association with thiamine deficiency (TD).

We report a case in which we found TD in a patient with advanced lung cancer who presented with weight loss, significant fatigue, and appeared to have a worsening general condition, for whom symptoms were dramatically improved within a short period of time by intravenous administration of thiamine.

The patient was a 76-year-old woman who had been diagnosed with lung cancer and liver metastases 6 months earlier. Due to interstitial pneumonia, she was not a candidate for chemotherapy and so palliative care was started. At 8 months after initial diagnosis, the patient complained of fatigue during a medical examination, so a blood sample was taken. A week later, she visited the hospital with a cane. She felt extremely fatigued and was unable to stand, but results from the previous blood test revealed that a TD. The fatigue disappeared 15 minutes after intravenous administration of thiamine and she was able to return home without the cane.

Fatigue is a frequent symptom in advanced cancer patients, and TD may be the underlying cause. Inclusion of TD in the differential diagnosis may contribute to improving patient QOL.

Despite increasing reports of thiamine deficiency (TD) among cancer patients, there remain some patients with borderline thiamine concentrations (BTC). However, it is unclear whether such patients subsequently develop TD.

Here, we report cases of cancer patients progressing to TD within a short time period after presentation with BTC (24–28 ng/ml).

A 49-year-old female with lung cancer. During treatment for depression, the patient showed a decreased appetite, and a blood sample revealed BTC (25 ng/ml). Fourteen days later, she reported a continued loss of appetite, and despite the absence of the 3 classical signs of Wernicke encephalopathy (WE), additional testing showed a thiamine level of 23 ng/ml, leading to a diagnosis of TD.

A 65-year-old female developed depression during chemotherapy for angiosarcoma. Her blood sample revealed BTC (25 ng/ml). Seven days later, despite the absence of the classical signs of WE, a further testing revealed a thiamine level of 20 ng/ml.

A 41-year-old female developed depression during chemotherapy for ovarian cancer. No loss of appetite was observed, but a blood sample revealed BTC (25 ng/ml). Seven days later, despite the absence of the classical signs of WE or decreased appetite, further testing revealed a thiamine level of 19 ng/ml.

Depressed cancer patients with BTC may develop TD within a short time frame. To prevent TD, health-care professionals should maintain an awareness of its potential and the need for regular testing of thiamine level or prophylactic replacement therapy.

It is well known that the burden on the families of cancer patient extends across many aspects, but there have been no reports of family members developing delirium due to the burden of caring for a cancer patient.

We reported a caregiver who developed Wernicke encephalopathy (WE) while caring for a family member with advanced cancer.

The subject was a 71-year-old woman who had been caring for her husband, diagnosed with gastric cancer and liver metastases, for 5 months. She visited the “caregivers’ clinic” after referral by an oncologist who was worried about a deterioration in her mental condition that had appeared several weeks previously. The woman had a history of diabetes mellitus. Some giddiness was observed and, based on her inability to answer questions, her level of consciousness was checked and some disorientation was observed. She was diagnosed with delirium. A blood sample was collected to investigate the cause of the delirium, but the test data showed no hypoglycemia. Her appetite had declined since her husband was diagnosed with cancer. Thiamine deficiency was suspected as thiamine stores in the body are depleted within about 18 days and her loss of appetite had continued for 5 months. On intravenous injection of 100 mg of thiamine, her consciousness level was returned to normal in 1 h. A diagnosis of WE was supported by the patient's abnormally low serum thiamine level.

The family members of cancer patients may develop a loss of appetite due to the burden of caring, resulting in WE. When providing care for signs of distress in family members, it is necessary to pay attention not only to the psychological aspects but also to their level of consciousness and physical aspects, particularly the possibility of serious illness resulting from reduced nutritional status.

Cancer patients often want to spend their final days at home, and it is essential that general practitioners have knowledge of and technical skills related to cancer medicine and symptom relief. Recent clinical studies have revealed that Wernicke encephalopathy (WE) is quite common in cancer patients. However, there have been no reports to date on WE in cancer patients undergoing home medical care.

From a series of cancer patient undergoing home medical care, we reported a patient with lung cancer who developed WE.

An 84-year-old female with lung cancer undergoing home medical care developed an impaired mental state and an attention deficit. Her symptoms fulfilled the diagnostic criteria for delirium. WE was suspected as the patient's food intake had fallen from normal a month previously to somewhere between 50% or just a few mouthfuls. This diagnosis was supported by abnormal serum thiamine and the disappearance of delirium after thiamine administration.

When delirium occurs in cancer patients undergoing home treatment, it is necessary to suspect thiamine deficiency as a potential cause, as appropriate diagnosis and treatment can prevent irreversible brain-related sequelae.

Nivolumab has become an effective treatment option for cancer in various sites; however, this drug may cause immune-related adverse effects due to its mechanism of action. Furthermore, little has been reported on thiamine deficiency (TD) in patients receiving nivolumab treatment.

From a series of cancer patients, we reported a patient with recurrent renal cell carcinoma who developed TD after the start of nivolumab treatment.

A 74-year-old man with recurrent renal cell carcinoma was referred to the psycho-oncology department as he had lost about 4 kg and displayed a loss of energy after four cycles of nivolumab treatment. Psychiatric interviews revealed a decrease in energy. Neurological examination did not reveal any impairment in consciousness, ataxia, or ocular symptoms. He did not develop appetite loss. The malabsorption or overconsumption of some nutrients is thought to occur due to the rapid loss of weight; thus, a reduction in vitamin B1, which has a short storage period in the body and is often deficient in cancer patients, was suspected. The diagnosis of TD was supported by the patient's abnormally low serum thiamine level.

In patients treated with nivolumab, it is necessary to pay careful attention to TD when proceeding with the treatment. It is hoped that future research may reveal the link between nivolumab administration and TD.

Thiamine deficiency (TD) is recognized in various kinds of disease with associated loss of appetite including cancer. However, it has not been recognized to date in bereaved partners after spousal loss from cancer.

From a series of bereaved partners who lost a spouse to cancer, we report on those who developed TD after bereavement.

Case 1 was a 57-year-old woman who sought consultation at our “bereavement clinic.” Her husband had been diagnosed with pancreatic cancer one year earlier and had died one month previously. At the first visit, she was observed to suffer depression, anxiety, and decreased appetite. Neurological, blood, and biochemical examinations did not reveal any noteworthy findings. She was diagnosed with uncomplicated bereavement. Detailed examination revealed that her appetite had been markedly decreased for approximately five weeks. The diagnosis of TD was supported by her abnormally low serum thiamine level. Case 2 was a bereaved 73-year-old male who had lost his wife to hypopharyngeal cancer one month previously after a five-year illness. He had shown a lack of energy for the month preceding his wife's death, but because there was no improvement after her death, his family recommended he seek consultation at our “bereavement clinic.” He was suffering from major depressive disorder. Detailed examination revealed that his appetite had been decreased for more than two weeks. Again, the diagnosis of TD was supported by his abnormally low serum thiamine level.

These reports demonstrate that there is a possibility that bereaved could develop TD after the loss of a loved one. TD should be considered whenever there is a loss of appetite lasting for more than 2 weeks, and medical staff should pay careful attention to the physical condition of the bereaved to prevent complications because of TD.

Thiamine deficiency (TD) is recognized in various kinds of disease with associated loss of appetite including cancer; however, TD has not been recognized in the family caregivers of cancer patients to date.

From a series of cancer patient caregivers, we reported an aged family caregiver who developed TD while caring for the cancer patient.

The caregiver was a 90-year-old male. He had been accompanying his wife, who was diagnosed with colon cancer 4 years previously, on hospital visits as the primary caregiver, but because of psychological issues, he was recommended to visit the psycho-oncology department's “caregiver's clinic” for a consultation. Detailed examination revealed that his appetite had been only about 50% of usual from about one year before, and he had lost 12 kg in weight in one year. The diagnosis of TD was supported by his abnormally low serum thiamine level.

This report demonstrates that there is a possibility that care providers could develop TD from the burdens associated with caregiving. TD should be considered whenever there is a loss of appetite lasting for more than 2 weeks, and medical staff should pay careful attention to the physical condition of care providers to prevent complications resulting from TD.

Although thiamine deficiency (TD) and Wernicke encephalopathy (WE) are not rare in cancer patients, the cases reported to date developed TD and/or WE after treatment had started.

From a series of cancer patients, we report a patient diagnosed with TD without the typical clinical symptoms of WE at the preoperative psychiatric examination.

A 43-year-old woman with ovarian cancer was referred by her oncologist to the psycho-oncology outpatient clinic for preoperative psychiatric evaluation. Her tumor had been growing rapidly before the referral. Although she did not develop delirium, cerebellar signs, or eye symptoms, we suspected she might have developed TD because of her 2-month loss of appetite as the storage capacity of thiamine in the body is approximately 18 days. The diagnosis of TD was supported by abnormally low serum thiamine levels.

Cancer therapists need to be aware that thiamine deficiency may occur even before the start of cancer treatment. In cases with a loss of appetite of more than 2 weeks’ duration, in particular, thiamine deficiency should be considered if the tumor is rapidly increasing, regardless of the presence or absence of delirium.

Wernicke encephalopathy (WE) is a neuropsychiatric disorder caused by thiamine deficiency, and is sometimes overlooked because of the diversity of clinical symptoms.

From a series of WE patients with cancer, we report a lung cancer patient who developed WE, the main symptom of which was agitation.

A 50-year-old woman with lung cancer was referred to our psycho-oncology clinic because of agitation lasting for three days. No laboratory findings or drugs explaining her agitation were identified. Although the patient did not develop delirium, ophthalmoplegia, or ataxia, WE was suspected because she experienced a loss of appetite loss lasting 5 weeks. This diagnosis was supported by abnormal serum thiamine and disappearance of agitation one hour after intravenous thiamine administration.

This report emphasizes the clinical diversity of WE and indicates the limits of the ability to diagnose WE from typical clinical symptoms. The presence of a loss of appetite for more than two weeks may be the key to the accurate diagnosis of WE.

Thiamine is an essential coenzyme for oxidative metabolisms; however, it is not synthesized in the human body, and the average thiamine storage capacity is approximately 18 days. Therefore, thiamine deficiency (TD) can occur in any condition of unbalanced nutrition. If TD is left untreated, it causes the neuropsychiatric disorder Wernicke encephalopathy (WE). Although WE is a medical emergency, it is sometimes overlooked because most patients with WE do not exhibit all of the typical symptoms, including delirium, ataxia, and ophthalmoplegia. If all of the typical clinical symptoms of WE are absent, diagnosis of TD or WE becomes more difficult.

From a series of cancer patients, we reported three patients who developed TD without the typical clinical symptoms of WE.

A 69-year-old woman with pancreatic body cancer receiving chemotherapy with paclitaxel and gemcitabine for six months. Her performance status (PS) was 1. A detailed interview revealed that she had appetite loss for six months. Another 69-year-old woman with ovarian cancer received nedaplatin; her PS was 0. A detailed interview revealed that she had appetite loss for three months. A 67-year-old woman with colon cancer receiving ramucirumab in combination with second-line fluorouracil with folinic acid and irinotecan. Her PS was 1. A detailed interview revealed that she had appetite loss for three weeks. None exhibited typical clinical signs of WE, but they developed appetite loss for six months, three months, and three weeks, respectively. The diagnosis of TD was supported by abnormally low serum thiamine levels.

This report emphasizes the possibility of TD in cancer patients even when patients do not develop typical clinical signs of WE. The presence of appetite loss for more than two weeks may aid in diagnosing TD. Patients receiving chemotherapy may be at greater risk for developing TD.

Wernicke encephalopathy (WE) is a neuropsychiatric disorder caused by thiamine deficiency. Several reports of WE in cancer patients are known. WE is sometimes overlooked because most patients do not exhibit its typical symptoms (e.g., delirium, ataxia, ocular palsy). If delirium is not present, a diagnosis of WE is difficult because delirium is the hallmark symptom of WE.

Taken from a series on WE in cancer, we report two patients who developed WE without delirium during periodic psycho-oncology outpatient visits.

Case 1. A 61-year-old woman with non-Hodgkin lymphoma who was periodically attending a psycho-oncology outpatient clinic developed an unsteady gait. WE was suspected because she also developed appetite loss for two weeks, and we could find no other laboratory findings to explain her unsteady gait. Our diagnosis was supported by abnormal serum thiamine and disappearance of the gait disturbance after intravenous thiamine administration. Case 2. A 50-year-old woman with breast carcinoma with bone metastasis developed an unsteady gait. WE was suspected because she also developed loss of appetite for two weeks, and no other laboratory findings could explain her unsteady gait. The diagnosis was supported by abnormal serum thiamine and disappearance of the gait disturbance after administration of intravenous thiamine.

Our report emphasizes the importance of being aware of WE, even when patients do not present with delirium. The presence of loss of appetite for more than two weeks may be the key to a diagnosis of WE.

Few reports of Wernicke encephalopathy in oncological settings have been published. Some cases of Wernicke encephalopathy are related to appetite loss; however, the degree to which loss of appetite leads to thiamine deficiency is not known.

A 63-year-old female with advanced cancer of the external genitalia was referred for psychiatric consultation because of disorientation, insomnia, and bizarre behaviors. Her symptoms fulfilled the diagnostic criteria for delirium. Routine laboratory examinations did not reveal the cause of the delirium. Thiamine deficiency was suspected because appetite loss had continued for 19 days since she had been admitted to hospital.

Intravenous administration of thiamine resulted in recovery from the delirium within three days. Serum thiamine level was found to be 16 ng/ml (normal range: 24–66 ng/ml). The clinical findings, the low level of thiamine in the serum, and the effective alleviation of delirious symptoms after thiamine administration fulfilled Francis's criteria for delirium induced by thiamine deficiency.

Clinicians must be aware of the possibility of Wernicke encephalopathy in cancer patients, especially in those with loss of appetite for longer than 18 days. The degree of appetite loss in such patients might serve as a reference. Early detection and intervention may alleviate the symptoms of delirium and prevent irreversible brain damage.