Keywords ketogenic diet - perillyl alcohol - intranasal administration - glioblastoma multiforme
- combination therapy - drug resistance
Palavras-chave dieta cetogênica - álcool perílico - administração intranasal - glioblastoma multiforme
- tratamento combinado - resistência medicamentosa
Introduction
Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor. Despite
standard-of-care therapy consisting of surgery and chemoradiation therapy, the disease
relapses in most patients, and the median survival is only of ∼ 15 months.[1 ] One of the major mechanisms of disease relapse in GBM patients has been attributed
to the enhanced ability of poorly differentiated glioma cells to invade and infiltrate
surrounding healthy tissue.[2 ]
[3 ] In this aspect, the vicinity and extension of the peritumoral edema (PTE) can be
useful to predict clinical outcomes in patients with a newly-diagnosed malignant glioma.[4 ]
Epilepsy develops in around 30–50% of patients with brain tumors as a consequence
of the brain swelling due to the edema accompanying the lesion. Epilepsy is a debilitating
condition that causes distress and adversely affects the patient's quality of life.[5 ]
[6 ] Antiepileptic drugs are commonly used to treat these patients; however, such treatments
are known to exert detrimental neuropsychological effects and often interact with
the therapeutic regimen, such as chemotherapeutic agents.[5 ]
[7 ] Several studies have attempted to address this issue by analyzing how changes in
the peritumoral tissue correlate with the onset of seizures in patients with brain
tumors. Mounting evidence suggests that epileptogenesis correlates with metabolic
alterations, acidosis and disruption of localized neural networks in the tumoral and
peritumoral areas of the brain.[8 ]
[9 ]
Recent studies have suggested that consumption of a ketogenic diet (KD) might play
a role in improving the outcomes of cancer patients undergoing treatment and in minimizing
the frequency of epileptic episodes.[10 ]
[11 ]
[12 ]
[13 ] The typical KD consists of low amounts of carbohydrates, moderate amounts of protein,
and high amounts of fat, aimed at stimulating fat metabolism while minimizing sugar
availability. Adherence to a KD promotes a unique metabolic state resulting from elevated
levels of fat-derived ketone bodies and lower levels of blood sugar, which have been
correlated with improved outcomes in patients with diabetes, cancer and certain neurological
disorders.[10 ]
[14 ]
[15 ] In addition, KDs have shown to reduce the frequency and severity of seizures in
epileptic patients.[12 ]
[16 ]
In the context of cancer, KDs are presumed to counteract the Warburg effect by depriving
tumor cells of glucose and improving mitochondrial activity.[10 ]
[17 ] The Warburg effect is characterized by a metabolic shift from aerobic respiration
toward increased glycolysis and lactate production, despite the availability of oxygen
(aerobic glycolysis).[18 ]
[19 ] Importantly, a major consequence of the Warburg effect is the increased cellular
consumption of glucose as the main source of energy. Nevertheless, this glycolytic
dependency may provide an opportunity for therapeutic intervention, based on the assumption
that a reduction in glucose availability may lead to a decline in proliferation and
metastatic capacity, along with increased sensitivity to cytotoxic or targeted therapies.[13 ]
[19 ]
[20 ] The shift in the ratio of ketone bodies over glucose is disadvantageous to tumor
cells, since glucose-addicted cancer cells are less likely to utilize ketone bodies
for energy, in contrast to normal cells, which can generate energy from either source.[21 ]
Emerging evidence indicates that KDs may have beneficial effects in patients with
malignant glioma. Results from a study in which adherence to a KD was combined with
standard chemoradiotherapy in a patient with GBM have demonstrated that the patient
went into complete remission while presenting with reduced blood glucose levels.[22 ] Subsequent case reports investigating this regimen have also shown a correlation
between reduced serum glucose levels and improved therapeutic responses.[16 ]
[17 ]
[23 ] Altogether, there is intriguing evidence correlating KD and metabolic reprogramming
with improved therapeutic responses to standard-of-care regimens for the treatment
of patients with malignant glioma.[13 ]
[17 ] We have published extensively on the antitumor effects of perillyl alcohol (POH),
a naturally occurring monoterpene related to limonene, in patients with recurrent
malignant glioma. A significant proportion of these patients, who had presented with
tumors refractory to standard chemoradiotherapy, responded favorably to the intranasal
delivery of POH.[24 ]
[25 ]
[26 ]
At the molecular level, reduced glucose availability may cause endoplasmic reticulum
(ER) stress, which triggers the unfolded protein response (UPR) cellular process,
consisting of an interplay of antagonistic mechanisms; the low to moderate activity
is cell-protective and supports chemo resistance, but more severe conditions aggravate
these mechanisms to the point in which the protective efforts are abandoned, and the
cell death program is induced instead.[27 ] As tumor cells frequently experience chronic stress conditions (due to hypoxia,
hypoglycemia, acidification, oxidative stress, etc.), the protective components of
their ER stress response are continuously engaged and thus, less able to neutralize
additional insults that trigger the ER stress response.[28 ]
[29 ] The ER stress/UPR process has been described as a potential therapeutic target in
GBM,[30 ] and this cellular mechanism has been demonstrated to be targeted by POH in GBM cells
in vitro.[31 ]
[32 ] It is thus conceivable that the concerted effect of KD-induced hypoglycemia together
with POH-induced responses may trigger severely aggravated ER stress, resulting in
tumor cell apoptosis.[22 ]
Based on our successful results in the clinical setting, we are now investigating
whether adherence to a KD during treatment with intranasal POH can further improve
the therapeutic outcomes of glioma patients. In this manuscript, we report a case
study of an adult patient with recurrent glioblastoma treated with this regimen.
Case Presentation
The present study was approved by our university (CAAE: 14613313.8.0000.5243), and
was performed at the university hospital. The patient signed a written informed consent
form prior to enrolling in the clinical trial combining KD with intranasal delivery
of POH to assess the therapeutic efficacy of this regimen. The POH was formulated
for intranasal delivery, and the preparation was supplied by a multidisciplinary laboratory
of Pharmaceutical Sciences at the Universidade Federal do Rio de Janeiro, according
to BR Patent Number PI 0107262–5. The KD was administered concomitantly with daily
inhalation of POH for three months. Perillyl alcohol (55 mg; 0.3% v/v) was administered
by inhalation 4 times a day, totaling 266.8 mg/a day.
A 54-year-old Caucasian man with no significant past medical record or family history
of brain tumor or neurological disorders presented with a seizure in September 2014.
A magnetic resonance imaging (MRI) brain scan revealed a regular space-occupying lesion
in the left temporal-parietal lobe that was enhanced with gadolinium. The patient
underwent a left temporal craniotomy with radical resection of the primary brain tumor
in January 2015. Following surgery, tumor resection was confirmed by an MRI scan.
The diagnosis of malignant glioma was confirmed based on complex histological features
characterized by ischemic necrosis and glomeruloid microvascular proliferation.
The immunohistochemical analysis was negative for O6-methylguanine-methyltransferase
(MGMT) methylation, and failed to detect mutations in the isocitrate dehydrogenase
(IDH) 1 and 2 genes. The patient underwent concomitant radiation therapy (59.4 Gy
total) with chemotherapy (temozolomide [TMZ] 75 mg every day for 6 weeks). Then, after
the conclusion of the radiation therapy, during the adjuvant phase, the patient received
TMZ (150–200 mg) on a 28-day cycle with 5 days on and 23 days off for 3 cycles. In
addition, the patient was treated for seizures and remained asymptomatic for eight
months. At this moment (September 2015) the patient presented with complaints of dizziness
and headache. A new brain MRI revealed the presence of a left temporal mass with an
intense surrounding vasogenic edema. The patient underwent an additional cycle of
TMZ treatment, but a new MRI scan showed no reduction in the tumor lesion. The treatment
was withdrawn in December 2015 because the patient was refractory to it, and presented
clinical adverse effects (headache, thrombocytopenia, seizures), with an MRI scan
showing no reduction in the tumoral lesion, and the patient was then considered out
of therapeutic possibilities and referred to supportive (palliative) treatment. In
January 2016, the patient was then enrolled in the clinical trial with KD in combination
with intranasal delivery of POH.
The anthropometric and biochemical status of the patient was assessed at the time
of inclusion in the study. The KD was prescribed according to the following distribution:
energy (25 kcal/kg); 1.5 g/kg protein; 25% carbohydrate; and 50% lipids (cholesterol
≤200 mg/day; saturated fat < 7%; polyunsaturated fat < 10%, monounsaturated fat < 20%,
and fibers between 20–30 g/day).[33 ] The levels of ketone bodies in the urine were measured (15 mg/dl), and confirmed
the adherence to the KD. The KD was well-tolerated, without relevant changes in nutritional
status, and no adverse symptoms were reported. The levels of ketone bodies remained
between 5–15 mg/dl throughout the duration of the treatment. A complete list of the
parameters analyzed before and 3 months after adherence to the KD are shown in ([Table 1 ]).
Table 1
Anthropometric and biochemical parameters before and after KD
Parameters
Before KD
Results
After KD
Results
Body mass (kg)
68.7
***
65.7
↓ 3 kg; ↓4.4%
BMI (kg/m2 )
23.7
eutrophic
22.7
eutrophic
WC (cm)
90.5
no risk of metabolic complications
80
no risk of metabolic complications
AC (cm)
30.5
94.4% (eutrophic)
27.5
85.1% (mild thinness)
TS (cm)
10
83.3% (mild thinness)
8
66.7% (severe thinness)
AMC (cm)
27.4
97.5% (eutrophic)
25
89% (mild thinness)
Biochemical Tests
Before KD
After KD
Reference Values
Total cholesterol (mg/dL)
211 mg/dL
170 mg/dL
normal range < 200 mg/dLa
LDL cholesterol (mg/dL)
113 mg/dL
93 mg/dL
normal range < 100 mg/dLa
HDL cholesterol (mg/dL)
80 mg/dL
61 mg/dL
normal range > 60 mg/dLa
Triglycerides (mg/dL)
92 mg/dL
81 mg/dL
normal range < 150 mg/dLa
Fasting glucose (mg/dL)
77 mg/dL
74 mg/dL
normal range < 100 mg/dLb
Urine ketone bodies
negative
positive
positive (5–150 mg/dL)
Abbreviations: AC, arm circumference (men age 50–54.9 years, P50 at 32.3 cm); adequacy
percentage of normal range 90–110%; mild thinness 80–90% (NHANES II); AMC, arm muscle
circumference (men aged 45–54.9 years, P50 at 28.1 cm); adequacy percentage of normal
range > 90%; mild thinness = 90% (NHANES II); BMI, body mass index (normal range (18.5–24.9);
(WHO, 1995; WHO, 1997); HDL, high-density lipoprotein; KD, ketogenic diet; LDL, low-density
lipoprotein; TS, triceps skinfold (men age 50–54.9 years, P50 at 12cm); adequacy percentage
of normal range 90–110%; severe thinness < 70% (NHANES II), WC, waist circumference
(men increased risk of metabolic complications ≥ 94 cm); Associação Brasileira para
Estudo da Obesidade e SíndromeMetabólica (ABESO, 2009).[4 ]
[5 ]
Notes: Biochemical tests: a V Brazilian Guideline to Dyslipidemias and Prevention of Atherosclerosis (2013); b Brazilian Guideline to Diabetes 2015–2016 (2015) Urine ketone bodies: ChoiceLine 10
Urinalysis – Roche.
At the end of the study, the patient presented with a weight loss of 4.36%; a decrease
in body fat of 8.5%, especially in the abdominal region (↓ 10 cm waist circumference
[WC]); an 8.8%-increase in water retention; and increases in bone mass (2%) and muscle
mass (1%). The KD reduced the total cholesterol level, the low-density lipoprotein
(LDL) cholesterol and the triglycerides levels, improving the lipid profile, although
it also reduced the high-density lipoprotein (HDL) cholesterol level. The fasting
blood glucose levels did not change ([Table 1 ]).
A follow-up MRI scan conducted after 3 months of KD combined with intranasal POH therapy
revealed marked reduction of the enhancing lesion ([Fig. 1 ]) and significant clinical improvement. At three months after the completion of the
therapeutic regimen, the patient was still being treated with low dose anti-seizure
medication but no steroidal drugs. There were no signs of delayed toxicity or adverse
events caused by the combined KD/intranasal POH treatment (data not shown).
Fig. 1 Effect of ketogenic diet concomitant with perillyl alcohol inhalation in recurrent
glioblastoma multiforme (GBM) patient. Representative magnetic resonance imaging (MRI)
scans show marked reduction of peritumoral edema and tumor size image after 3 months
of treatment (B, D, F ) in comparison with the first image obtained before the treatment (A, C, E ). Brain MRI axial fluid-attenuated inversion recovery (FLAIR) (A-D ) and T1-weighted image (T1W) with contrast (E, F ).
Discussion
Herein we report a case study of a patient with recurrent GBM that has been successfully
treated with KD concomitantly with POH inhalation for three months without any side
effects. As a result, the patient showed tumor regression and reduced peritumoral
edema, which led to an overall improvement in quality of life and lower frequency
of seizures.
The severity of the peritumoral brain edema significantly influences the glioma prognosis
by promoting tumor cell invasion and increasing morbidity.[4 ]
[25 ] Increased diffusion of extracellular matrix components rich in proteases and tumor-derived
growth factors into the peritumoral stroma during tumor progression further modifies
the microenvironment and promotes neovascularization.[34 ] Since the reduction in the peritumoral edema in animals that were fed the KD appears
to be correlated with a decrease in the expression levels of several proteins involved
in malignant progression, adherence to a KD might also represent a relevant tool to
halt tumor progression.[35 ] Our results showing a marked reduction in the peritumoral edema following our therapeutic
regimen combining the administration of a KD and intranasal POH were encouraging and
consistent with the literature, suggesting that the extent of the peritumoral edema
may impact the overall survival in patients with GBM.[2 ]
[36 ]
Moreover, our results demonstrating a reduction in the frequency of seizure episodes
in a patient with recurrent GBM following combined administration of the KD and intranasal
POH are consistent with an increasing body of data demonstrating the value of using
a KD to manage patients with intractable epilepsy.[12 ]
[37 ] Importantly, seizures are often refractory to medication in patients with GBM, and
can persist after surgery.[8 ] This is a major concern in the management of patients with GBM, as epilepsy develops
in 29–49% of the patients diagnosed with brain tumors.[7 ]
[38 ] In this context, tumor-related epilepsy is a condition that requires an integrated
treatment approach due to the severity of the disease.[39 ] An adequate high-fat, low-carbohydrate, protein-based KD might be useful in the
treatment and management of brain tumors because it appears to interfere with key
epileptogenic mechanisms involving changes in pH, neurotransmitters, ion levels, and
in the expression of voltage-dependent channels and receptors in the tumoral and peritumoral
brain tissues.[9 ]
[21 ]
Overall, the results of this study demonstrated that the KD was well-tolerated and
compatible with previous clinical findings. The KD-induced hypoglycemia can potentially
be an adjuvant to standard treatments, such as surgery and chemoradiation, and also
possibly to novel regimens, such as intranasal POH, in the recurrence setting.
