The American Society of Clinical Oncology (ASCO) has updated its guideline for antiemetics in oncology to provide updated recommendations for preventing chemotherapy-induced nausea and vomiting (CINV) and radiation-induced nausea and vomiting (RINV). The update is based on a systematic review of the medical literature, including randomized controlled trials and systematic reviews from the Cochrane Collaboration. Key recommendations include: 1. **Highly Emetic Chemotherapy**: Patients receiving combined anthracycline and cyclophosphamide regimens should receive a combination of a neurokinin 1 (NK1) receptor antagonist, a 5-HT3 receptor antagonist, and dexamethasone. Fosaprepitant, a single-day intravenous formulation, is validated as an acceptable NK1 receptor antagonist. 2. **Moderately Emetic Chemotherapy**: The recommended regimen is a two-drug combination of palonosetron and dexamethasone. If palonosetron is unavailable, first-generation 5-HT3 receptor antagonists can be used. 3. **Low Emetic Chemotherapy**: A single 8-mg dose of dexamethasone before chemotherapy is suggested. 4. **Minimally Emetic Chemotherapy**: No routine antiemetic is recommended before or after chemotherapy. 5. **Combination Chemotherapy**: Antiemetics appropriate for the most emetogenic agent should be administered. 6. **Adjunctive Drugs**: Lorazepam and diphenhydramine are useful adjuncts but not recommended as single-agent antiemetics. 7. **Complementary and Alternative Medicine**: No published randomized controlled trials support the use of complementary and alternative medicine therapies for CINV prevention. For radiation therapy, the update emphasizes the importance of using a 5-HT3 receptor antagonist before each fraction and for at least 24 hours after completion, with a 5-day course of dexamethasone during fractions 1 to 5. The guideline also addresses special populations, such as pediatric patients and those undergoing high-dose chemotherapy with stem-cell or bone marrow transplantation, and provides recommendations for managing nausea and vomiting in these settings.The American Society of Clinical Oncology (ASCO) has updated its guideline for antiemetics in oncology to provide updated recommendations for preventing chemotherapy-induced nausea and vomiting (CINV) and radiation-induced nausea and vomiting (RINV). The update is based on a systematic review of the medical literature, including randomized controlled trials and systematic reviews from the Cochrane Collaboration. Key recommendations include: 1. **Highly Emetic Chemotherapy**: Patients receiving combined anthracycline and cyclophosphamide regimens should receive a combination of a neurokinin 1 (NK1) receptor antagonist, a 5-HT3 receptor antagonist, and dexamethasone. Fosaprepitant, a single-day intravenous formulation, is validated as an acceptable NK1 receptor antagonist. 2. **Moderately Emetic Chemotherapy**: The recommended regimen is a two-drug combination of palonosetron and dexamethasone. If palonosetron is unavailable, first-generation 5-HT3 receptor antagonists can be used. 3. **Low Emetic Chemotherapy**: A single 8-mg dose of dexamethasone before chemotherapy is suggested. 4. **Minimally Emetic Chemotherapy**: No routine antiemetic is recommended before or after chemotherapy. 5. **Combination Chemotherapy**: Antiemetics appropriate for the most emetogenic agent should be administered. 6. **Adjunctive Drugs**: Lorazepam and diphenhydramine are useful adjuncts but not recommended as single-agent antiemetics. 7. **Complementary and Alternative Medicine**: No published randomized controlled trials support the use of complementary and alternative medicine therapies for CINV prevention. For radiation therapy, the update emphasizes the importance of using a 5-HT3 receptor antagonist before each fraction and for at least 24 hours after completion, with a 5-day course of dexamethasone during fractions 1 to 5. The guideline also addresses special populations, such as pediatric patients and those undergoing high-dose chemotherapy with stem-cell or bone marrow transplantation, and provides recommendations for managing nausea and vomiting in these settings.