Professor Jun Zhou: Managing Side Effects of Chemotherapy, Targeted Therapy, and Immunotherapy for Gastric Cancer — What You Can Handle at Home and When to Seek Care

Summary: Side effects during cancer treatment are often preventable, manageable, and reversible, and appropriate management can make a meaningful difference to quality of life. Professor Jun Zhou of Shanghai GoBroad Cancer Hospital, Affiliated to China Pharmaceutical University, reviews three major categories of treatment-related side effects in gastric cancer: gastrointestinal symptoms, myelosuppression, and liver toxicity from chemotherapy; hypertension, bleeding, thrombosis, and proteinuria from targeted therapy; and thyroid dysfunction, immune-related myocarditis, and other immune-related adverse events from immunotherapy. The article also highlights less obvious complications such as interstitial lung disease/pneumonitis and identifies six situations in which patients should seek medical care promptly, including fever above 38.5°C, breathing problems, cardiac symptoms, inability to maintain food or fluid intake, neurologic symptoms, and gastric-cancer emergencies such as bleeding, obstruction, or perforation.

Cancer treatment is often a long journey. In addition to the disease itself, treatment-related side effects can be difficult for patients and families to manage. Nausea, vomiting, fatigue, hand-foot syndrome, diarrhea, and constipation do not simply have to be endured. With appropriate management, many of these symptoms can be reduced and quality of life can be improved.

For this article, we invited Professor Jun Zhou, Deputy Medical Director and Director of Gastrointestinal Oncology at Shanghai GoBroad Cancer Hospital, Affiliated to China Pharmaceutical University, to explain how patients can recognize and manage common side effects during gastric cancer treatment.

Q1: What are the most common side effects of gastric cancer treatment, and how can patients manage them at home?

Professor Jun Zhou: The first thing I want patients to know is that having side effects does not mean the treatment has failed, and it does not mean your body cannot tolerate treatment. Most treatment-related side effects can be prevented, managed, or reversed. The key is to recognize them early and intervene early.

Treatment options for gastric cancer have expanded considerably — from the chemotherapy era decades ago, to targeted therapy, immunotherapy, and now emerging approaches such as CAR-T cell therapy. Different treatments have different side-effect profiles. Let me go through some of the issues patients encounter most often.[1-5]

1. Chemotherapy-Related Side Effects

Many of the side effects traditionally associated with gastric cancer treatment come from chemotherapy. Common examples include:

Gastrointestinal side effects: Nausea and vomiting are among the most common. They often occur soon after chemotherapy and can make it difficult to eat. Some patients may also develop constipation or diarrhea.

Bone marrow toxicity: This can cause low white blood cell counts, low platelet counts, and anemia. Decreases in white blood cells and platelets are particularly common. Anemia is already common in patients with gastric cancer and may become more pronounced after chemotherapy.

Liver toxicity: Many anticancer drugs are metabolized by the liver and may cause liver injury, which can show up as elevated liver enzymes and, in some cases, increased bilirubin.

Hair loss: This usually has little direct effect on physical health and is reversible in most cases.

2. Targeted Therapy-Related Side Effects

With the use of targeted therapies, the range of side effects seen in gastric cancer has become more diverse.

For example, ramucirumab and fruquintinib are commonly used in later-line treatment settings. Potential side effects include hypertension, bleeding, thrombosis, and proteinuria.

3. Immunotherapy-Related Side Effects

Immunotherapy is now widely used in gastric cancer in China, and immune-related adverse events can affect many different organs. Common issues include:

Endocrine changes: Thyroid dysfunction is among the most common. Some patients may initially develop hyperthyroidism, which can cause irritability or restlessness, and later develop hypothyroidism, which may cause fatigue and excessive sleepiness. These problems can usually be managed with appropriate medication.

Immune-related myocarditis: This is rare — occurring in fewer than 0.5% of patients according to the source article — but it can be serious. Careful assessment before immunotherapy is therefore important, especially in patients with active autoimmune disease.

Immune-related adverse events can also affect the liver, spleen, lungs, kidneys, joints, and other organs.

Whatever the type of side effect, regular monitoring, early recognition, and timely management are essential. The goal is to minimize the impact of adverse events while allowing treatment to continue as safely as possible.

Q2: Are there less common side effects that patients with gastric cancer should pay particular attention to?

Professor Jun Zhou: Some treatment-related side effects can be relatively difficult to notice at first. One important example is interstitial lung disease (ILD)/pneumonitis, which may be associated with antibody-drug conjugates (ADCs), immunotherapy, radiotherapy, or other treatments. It is often detected through chest CT imaging.[6]

If regular CT follow-up is difficult, pay close attention to new symptoms such as chest tightness, a persistent dry cough, or a noticeable decline in exercise tolerance. If these occur, contact your medical team and arrange appropriate evaluation promptly.

Whether you are in the hospital or at home, paying attention to changes in your body is an important part of self-management. Recognizing treatment-related adverse events early can help keep treatment safer.

Q3: Which symptoms require a hospital visit, and which mild side effects can usually be managed at home?

Professor Jun Zhou: This question is more important than any single medication or home-management tip. There are several situations in which patients should seek medical care promptly:

1. Fever. If your temperature is above 38.5°C, go to the hospital for a complete blood count and biochemical tests. In particular, the medical team will need to check whether white blood cell and neutrophil counts have fallen significantly. When these counts are very low, the risk of serious bacterial infection can rise sharply. Do not wait at home for a high fever to pass.

2. Breathing problems. Chest tightness, shortness of breath, a dry cough, or coughing up blood may indicate a serious lung complication such as interstitial lung disease/pneumonitis. This is particularly important for patients receiving ADC therapy. Seek medical evaluation promptly if these symptoms occur.

3. Cardiac symptoms. New palpitations, an irregular heartbeat, or the feeling that your heart is racing or pounding unusually hard should be evaluated as soon as possible. Serious cardiac complications can progress quickly.

4. You cannot maintain basic food or fluid intake. Severe vomiting or diarrhea can make it impossible to eat or drink and may lead to dehydration or electrolyte imbalance. Hospital assessment may be needed so fluids and electrolytes can be replaced appropriately.

5. Neurologic symptoms. New confusion or drowsiness, weakness or difficulty moving the arms or legs, memory changes, or slurred speech require medical evaluation. These symptoms may have several possible causes, including stroke or brain metastases, and should not be managed at home.

6. Gastric Cancer Emergencies

a) Bleeding. Tumor-related bleeding can cause major upper gastrointestinal hemorrhage, with symptoms such as vomiting blood, black stools, or even low blood pressure and shock. Significant tumor-related bleeding cannot be managed safely at home. Contact your treating team immediately; if they cannot be reached, go to the emergency department of a hospital equipped to provide urgent care.

b) Obstruction. Gastric outlet obstruction is a common form of obstruction in gastric cancer. Food can accumulate in the stomach and may also place pressure on nearby organs. If obstruction is suspected, the source article advises stopping food and fluid intake and going to the hospital for assessment and treatment. Management may include drainage, stent placement, or palliative surgery, depending on the situation.

c) Perforation. Gastric cancer can cause gastric perforation, and tumors that have spread within the abdomen may also lead to intestinal perforation. Patients often develop sudden, severe pain. The pain may temporarily ease, but this does not mean the condition is improving; digestive contents may still be leaking into the abdominal cavity and causing ongoing injury. This is an emergency and requires immediate hospital evaluation.

Milder side effects — such as mild nausea, diarrhea, constipation, fatigue, or hand-foot syndrome — may often be managed at home according to the care plan provided by your medical team. Keep a record of what happened, when it started, how severe it was, and what you did to manage it, and share that information at your next appointment.

One final message: if you are unsure whether a symptom is important, tell your doctor. Experienced clinicians are rarely concerned that patients ask too many questions; what worries them is hearing “everything was fine” only after a problem has become severe. Good symptom management can help treatment continue more safely and steadily.

This article is based on the references below and is intended for general education only. Please follow the recommendations of your treating physician for your individual treatment and side-effect management plan.

References:

[1] Chinese Society of Clinical Oncology (CSCO) Guidelines for the Prevention and Treatment of Anticancer Therapy-Related Nausea and Vomiting (2025).

[2] https://www.cancer.org/cancer/managing-cancer/side-effects/fatigue-weakness-sleep/fatigue.html

[3] https://www.cancer.org/cancer/managing-cancer/side-effects/hair-skin-nails/hand-foot-syndrome.html

[4] https://www.cancer.org/cancer/managing-cancer/side-effects/stool-or-urine-changes/constipation.html

[5] https://www.cancer.org/cancer/managing-cancer/side-effects/stool-or-urine-changes/diarrhea.html

[6] Zhou C, Deng H, Yang Y, et al. Cancer therapy-related interstitial lung disease. Chinese Medical Journal. 2025;138(3):264-277.