Treating Advanced and Recurrent Disease

When endometrial cancer is advanced (Stage III or IV) or returns after initial treatment, the focus shifts to systemic therapy. This means using medications that travel throughout the entire body to find and attack cancer cells wherever they may be. In recent years, the addition of immunotherapy to traditional chemotherapy has significantly changed the outlook for patients with advanced disease.

First-Line Treatment: Chemo-Immunotherapy

The standard “backbone” of treatment for advanced endometrial cancer is a combination of two chemotherapy drugs: carboplatin and paclitaxel ^[1]. These are typically given every three weeks for six cycles.

Recent large-scale trials (RUBY and NRG-GY018) have shown that adding an immunotherapy drug—either dostarlimab or pembrolizumab—to this chemotherapy is more effective than chemotherapy alone ^[1][2]. The exact drug choice depends on whether the disease is newly advanced or recurrent, your MMR status, prior immunotherapy exposure, local approvals, and other health factors.

• dMMR/MSI-H Tumors: Patients with “mismatch repair deficient” tumors see a profound benefit. In the RUBY trial, those receiving dostarlimab with chemotherapy had a 61.4% chance of being alive without the cancer growing at 24 months, compared to only 15.7% for those who had chemotherapy alone ^[1][3].
• pMMR/MSS Tumors: While the benefit is less pronounced than in dMMR cases, patients with “proficient” repair tumors still see a delay in the cancer’s return when immunotherapy is added ^[2][4].

After the initial six cycles of chemotherapy are finished, patients often continue on “maintenance” immunotherapy (dostarlimab or pembrolizumab). The maintenance duration is drug- and situation-specific, though it can last for up to two or three years depending on response and tolerability ^[1][2].

Targeted Therapy for pMMR Recurrence

If the cancer returns or continues to grow after platinum-based chemotherapy, and the tumor is pMMR (the more common type), a combination of pembrolizumab and lenvatinib is an option for appropriately selected patients who have not already received prior immunotherapy ^[5]. (If you have already received a checkpoint inhibitor, your oncologist must review your entire treatment history before recommending the next step).

Lenvatinib is a tyrosine kinase inhibitor (TKI), a type of targeted therapy that blocks the signals cancer cells use to grow and form blood vessels ^[6]. In the KEYNOTE-775 trial, this combination nearly doubled the time before the cancer progressed compared to standard chemotherapy (6.6 months vs. 3.8 months) ^[7].

Managing Serious Side Effects

While these treatments are powerful, they can cause significant and sometimes permanent side effects. Understanding these “red flags” is essential for your safety. Never wait for a routine appointment to report a new symptom. Call your oncology team immediately.

Chemotherapy Safety

During chemotherapy, ask your team for their specific fever threshold (often 100.4°F or 38.0°C). A fever during chemotherapy is a medical emergency that requires immediate evaluation.

Lenvatinib-Specific Toxicities

Lenvatinib is a daily pill that requires very close monitoring ^[7]:

• Hypertension (High Blood Pressure): This is very common, affecting many patients, with a significant portion experiencing severe hypertension ^[8]. You must monitor your blood pressure daily at home using a written plan from your doctor detailing when to take medication, when to hold a dose, and when to call the clinic.
• Diarrhea: This can lead to severe dehydration if not managed quickly ^[6].
• Hypothyroidism: Lenvatinib often causes the thyroid gland to underperform, leading to extreme fatigue, weight gain, and feeling cold ^[7]. Your doctor will check your thyroid levels frequently and may prescribe hormone replacement.

Immune-Related Adverse Events (irAEs)

Immunotherapy works by “unleashing” your immune system to fight cancer, but it can also cause the immune system to attack your own healthy organs ^[9]. These effects can happen months or even a year after treatment ends ^[10].

• Adrenal Insufficiency: If the immune system attacks the adrenal glands, it can cause life-threatening low blood pressure, extreme weakness, and confusion ^[11].
• Pneumonitis: Inflammation of the lungs that can cause a new cough or shortness of breath ^[12].
• Colitis: Severe inflammation of the bowel causing abdominal pain and frequent, watery diarrhea ^[13].
• Hepatitis: Inflammation of the liver, often caught early through blood tests before you feel symptoms ^[14].

Monitoring and Safety Checklist

Because of these risks, you will have frequent blood work and check-ups. Do not wait for a routine call-back if you have emergency symptoms.

Go to the ER (or call emergency services) for:

• [ ] Chest pain, severe weakness/fainting, or rapidly worsening breathlessness ^[12].
• [ ] Fever during active chemotherapy (per your clinic’s guidelines).
• [ ] Markedly reduced urine output or severe jaundice.

Call the 24-hour Oncology Number Immediately for:

• [ ] Severe fatigue or “crashing” that makes it hard to stand up (could be adrenal or thyroid issues; may require lifelong hormone replacement) ^[11].
• [ ] Shortness of breath or a new, dry cough ^[12].
• [ ] Severe diarrhea (more than 4-6 times a day) or blood in your stool ^[13].
• [ ] Headaches or blurred vision (signs of very high blood pressure) ^[6].
• [ ] Confusion or sudden changes in your mental state ^[11].

Most of these side effects are manageable if caught early, often by temporarily stopping the drug or starting a course of steroids to calm the immune system, though some endocrine issues require lifelong hormone replacement ^[12][13].

Note: Some isolated or limited recurrences may be managed with surgery or radiation, and hormonal therapy or clinical trials may also be relevant depending on histology and biomarkers.