Nausea is a very complex symptom involving numerous pathways between the brain and the gut, and it can have many different causes. While chemotherapy is a big culprit in causing nausea and vomiting, there are multiple other causes unique to cancer. Here are few that stand out:

* Radiation-induced nausea and vomiting occurs when a portion of the GI tract (including the esophagus) are located in the field of radiation. The primary treatment will depend on what part of the GI tract is affected; for example, acid reducers are helpful if the stomach or esophagus have been inflamed from radiation therapy plus general anti-nausea medications.

* Intestinal obstruction is a very serious complication of cancer which can occur due to prior cancer surgeries (scar tissue can cause the intestines to twist and obstruct) or due to the cancer itself causing a blockage. This can warrant surgery at times if the obstruction cannot reverse itself on its own.

* Brain involvement of the cancer can cause nausea and vomiting due to swelling and increased pressure on the brain. Steroids, like dexamethasone, help reduce the swelling, and they are often used concurrently with tumor-directed treatments.

* Uncontrolled pain, regardless of its location, can cause nausea and vomiting. Compounding this, opioid medications (like morphine) can also contribute. This is often transient, for the first few days of use, but it can sometimes be more persistent.

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  While nausea and vomiting are common symptoms for many patients, patient with cancer often have multiple contributing factors for their nausea, not only from the disease itself but from the treatments. This two-part post will be looking at nausea and vomiting specifically with an eye towards cancer, the first part on chemotherapy-induced nausea and vomiting (CINV) and the second part on other types of nausea and vomiting.

   Why does chemotherapy induce nausea and vomiting? There are several different ways this happens. One way is through the “chemoreceptor trigger zone,” or CTZ, which gets triggered by exposure to drugs via the blood and cerebrospinal fluid—this activates the command center for vomiting. The other major way is via damage to the intestines themselves by the chemotherapy; the damage to the gut triggers vomiting, both by sending signals to the brain and back to the gut itself.

  CINV is usually categorized by the timing of the nausea/vomiting related to the administration of the chemotherapy—acute (within the first 24 hours of receiving chemotherapy) and delayed (after the first 24 hours ). There can also can be anticipatory nausea and vomiting occurring prior to the chemotherapy (based on a learned response from earlier chemotherapy), but this is less common.

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