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Medically reviewed by C.H. Weaver M.D. Medical Editor 1/2021

Weight loss is a common complication of cancer and cancer treatments that can result in a poor prognosis for patients. Cancer or cancer treatments first cause a loss of appetite or aversion to food, also known as anorexia, which then may lead to drastic weight loss.

  • What is anorexia?
  • What causes anorexia in cancer patients?
  • Why is it important to manage anorexia and weight loss?
  • How can anorexia and weight loss be managed?

What is anorexia?

Anorexia is a loss of appetite or aversion to food, which can lead to drastic weight loss. Anorexia can compromise your ability to get adequate nutrition through food sources. When you do not take in adequate calories and nutrients, your body is forced to “burn” fat and muscle stores, which is why you lose weight.

What causes anorexia in cancer patients?

While not all cancer patients will develop anorexia and subsequent weight loss, anorexia and weight loss are very common. Anorexia may result from the cancer, chemotherapy, radiation or a variety of other causes, including physical and psychological causes.

Anorexia that is a direct result of the cancer occurs in the majority of patients with advanced-stage cancers. For these patients, the cancer has changed the way their metabolism works, dramatically impacting their weight. In addition, cancer can have psychological and social impacts that cause stress and changes in eating patterns. These changes can lead to anorexia and weight loss.

In many cases, cancer treatment, rather than the cancer itself, will cause anorexia. Both chemotherapy and radiation therapy cause a variety of side effects that can lead to anorexia and weight loss, such as nausea and vomiting, fatigue, changes in how things taste and a dry mouth. In addition, cells in the body release tumor necrosis factor (TNF) and interleukin-1 in an attempt to fight the cancer, both of which cause anorexia. Destruction of cancer cells by radiation therapy increases levels of TNF and interleukin-1, resulting in anorexia and weight loss.

Why is it important to manage anorexia and weight loss?

Anorexia and the resulting weight loss compromises your health, often weakening your immune system and causing great discomfort and dehydration. As a result, cancer treatment may need to be reduced or delayed, which results in the delivery of treatment that is not optimal.

In an evaluation of 12 different studies involving 3,047 patients, the Eastern Cooperative Oncology Group found that loss of more than 5% of pre-cancer weight predicted a poor prognosis for cancer patients. In addition, this weight loss was associated with a lower response to chemotherapy.1

Not only can anorexia interfere with treatment, it can cause concern for both you and your family. Any attempts to prevent or manage anorexia can improve your health and provide you and your family with a sense of well-being.

How can anorexia and weight loss be managed?

The best way to manage anorexia and weight loss is to prevent them from occurring in the first place. However, sometimes these symptoms are inevitable results of cancer and cancer treatment. Some approaches that may help prevent anorexia and weight loss may include:

  • Control of nausea and vomiting
  • Stimulate appetite
  • Maintain adequate nutrition

Control Nausea and Vomiting:

Both chemotherapy and radiation therapy cause nausea and vomiting, which can lead to anorexia and weight loss. The key to controlling nausea and vomiting is to prevent it before it occurs. Many new anti-vomiting drugs, called antiemetics, are very effective for preventing or decreasing nausea and vomiting. Antiemetics may be used alone or in combinations. Antiemetics are typically administered 24 hours prior to chemotherapy and then continued until 24 hours after chemotherapy. In addition, some patients may wish to consider non-drug methods to help with nausea and vomiting.

Appetite Stimulants

A variety of appetite stimulants may help you to maintain adequate calorie and nutrient intake from food sources. These include Marinol®, megestrol acetate (Megace®) and dexamethasone.

Marinol®: Marinol® is part of a class of drugs called cannabinoids. Dronabinol, the active ingredient in Marinol® is produced in the laboratory and is a version of a naturally occurring substance in Cannabis sativa L. (marijuana). Marinol® is known to be an appetite stimulant. Also, Marinol® is thought to directly block a receptor that is involved in chemotherapy-induced nausea and vomiting. Because of these two effects, Marinol® may be beneficial to patients receiving chemotherapy treatments.

In 139 patients with anorexia and weight loss, Marinol® significantly increased appetite after 4 weeks. There was a total increase in appetite of 38% for patients receiving Marinol® compared to 8% for patients receiving placebo. The patients receiving Marinol® also tended to have decreased nausea and improved body weight and mood.2 Marinol® has also been proven to reduce chemotherapy-induced nausea and vomiting in cancer patients.3

Unlike marijuana, Marinol® provides standardized THC concentrations and does not contain the other 400 uncharacterized substances found in smoked marijuana, such as carcinogens or fungal spore. It is not associated with the quick high of smoked marijuana. However, you should not drive, operate machinery or engage in any hazardous activity until it is established that you can tolerate the drug and perform such tasks safely. Marinol® is FDA-approved and is administered orally in capsule form.

Megestrol Acetate (Megace®): Megace® is a progesterone, or steroid hormone, that improves appetite in patients with advanced cancer. Megace® is FDA-approved for the palliative treatment of advanced breast and endometrial cancer.

Several studies have established that Megace® causes appetite stimulation and weight gain in cancer patients with anorexia. In a North Central Cancer Treatment Group trial, patients who received Megace® experienced an increase in both appetite and non-fluid weight.4 Furthermore, 13 out of 15 placebo-controlled trials evaluating Megace® demonstrated that it improves appetite in cancer patients.

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Megace® is associated with some side effects. Megace® suppresses some endocrine functions and presents a slightly increased risk for thrombophlebitis, an inflammation of veins that is often accompanied by blood clots. Patients receiving Megace® who experience serious infection or trauma may require supplemental corticosteroids to reduce inflammation.

Dexamethasone: Dexamethasone is a corticosteroid that is often prescribed for cancer-associated anorexia. Corticosteroids are substances produced by the adrenal gland which serve important functions in the body, including regulating metabolism and reducing inflammation. In a randomized, placebo-controlled trial, dexamethasone was found to improve appetite in patients with advanced cancer.5 A study that compared several different drugs that stimulate appetite indicated that dexamethasone and Megace® produced equivalent improvement in appetite.4 However, dexamethasone was associated with significantly worse side effects, such as myopathy, which is an abnormal condition of skeletal muscle characterized by muscle weakness and other changes in the muscle tissue. As a result, dexamethasone is not recommended for chronic use, but appears to be beneficial for some cancer patients with a poor prognosis, as serious side effects are unlikely to occur in the short term.

Megestrol Acetate and Marinol Improve Appetite in Patients With Cancer-Associated Anorexia

According to the results of a recent study conducted by the North Central Cancer Treatment Group (NCCTG), both the hormonal agent Megestrol Acetate and the cannabinoid Marinol improved appetite in patients with cancer-associated anorexia.

Anorexia is the lack or loss of appetite, which results in the inability to eat and can lead to drastic weight loss. Anorexia can result from psychological, physical and a variety of other causes. Anorexia is a common problem in cancer patients and can compromise treatment and result in a poor prognosis for patients.

More than half of patients with advanced cancer suffer from anorexia. There are currently several ways to manage anorexia including nutritional support to increase caloric intake and the use of antiemetics to control nausea and vomiting associated with chemotherapy and radiation. In addition, orexigenic agents help to stimulate appetite and are often used to treat anorexia. There are several different types of orexigenic agents including cannabinoids, progesterones and corticosteroids.

Both Marinol and Megestrol Acetate are orexigenic agents. Marinol, an appetite stimulant, is part of a class of drugs collectively referred to as cannabinoids. Marinol is believed to stimulate appetite and directly block the cannabinoid-1 receptor in the brain that is responsible for chemotherapy-induced nausea and vomiting. Megestrol Acetate is a progesterone, or steroid hormone, that improves appetite in patients with advanced cancer.

This most recent study evaluated both Marinol and Megestrol Acetate for improving appetite in cancer patients with anorexia. The study involved 469 cancer patients with an ongoing problem of anorexia and/or weight loss. The study had three arms: one group took Megestrol Acetate, another group took Marinol and a final group took both.

The results indicated that 73% of patients taking Megestrol Acetate reported an improved appetite, compared with 47% in the Marinol group and 70% in the combination group. Megestrol Acetate did, however, cause severe side effects, with 18% of patients in the Megestrol Acetate group experiencing impotence, compared with 14% in the combination group and only 4% in the Marinol group. Furthermore, 18% of patients in the Megestrol Acetate group experienced fluid retention, compared with 13% in the combination group and 11% in the Marinol group.

The results of this study indicate that both Megestrol Acetate and Marinol stimulate appetite in patients with cancer-associated anorexia. Marinol has an additional advantage in that it is an antiemetic and is FDA-approved for the treatment of chemotherapy-induced nausea and vomiting. Clinical studies are ongoing to evaluate the effectiveness of both of these orexigenic agents and to establish optimal dosing for Marinol, as patients in this study received a low dose of Marinol.

Nutritional Support

Since anorexia can compromise your ability to get adequate nutrition through food sources, you may benefit from treatment with nutritional support. All cancer patients should meet with a nutritionist or registered dietician prior to and throughout their treatment to help maintain their health through appropriate alterations to their diet.

Your nutritionist may recommend that you focus on eating higher calorie foods, such as protein-rich foods. For example, you may try including more of the following in your diet:

  • Protein drinks (powdered protein supplement mixed with fruit, milk and/or yogurt)
  • Milk
  • Dairy products
  • Eggs
  • Meat
  • Sauces or gravies
  • Oil

In some situations, you may require caloric supplementation beyond what you can get through altering your diet. Nutritional support is beneficial to patients both prior to and during treatment. Nutritional support may be administered into the veins through parenteral nutrition, or directly into the intestines with enteral nutrition. Both of these types of nutritional support appear to be most beneficial to patients undergoing stem cell transplantation.

Total parenteral nutrition: Total parenteral nutrition refers to the intravenous (into your vein) delivery of a nutritionally adequate solution. Total parenteral nutrition is used for patients who cannot eat and may be beneficial in the perioperative setting for cancer patients with severe malnutrition; however, long-term of total parenteral nutrition for patients undergoing chemotherapy is strongly discouraged, as it does not appear to offer any benefit. Patients undergoing stem cell transplantation appear to receive the greatest benefit from total parenteral nutrition.

Enteral nutrition: Enteral nutrition refers to the delivery of nutrients directly into the gastrointestinal tract and is used when a patient cannot ingest, chew, or swallow food, but can digest and absorb nutrients. Enteral nutrition appears to be beneficial for patients undergoing stem cell transplantation.


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