ASCO 2026 Highlights: Can Fasting During Chemotherapy Help Fight Ovarian Cancer?

People with high-grade serous ovarian carcinoma (HGSOC), the most common and aggressive type of ovarian cancer, often need better, safer, and more affordable treatments. Doctors continue to search for ways to improve care.

A small clinical trial in Rome, Italy, presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, suggests that short-term fasting before and after chemotherapy may be beneficial. Fasting lowers insulin levels, which could make chemotherapy more effective and help patients stay cancer-free longer.

Why Insulin Matters in Cancer Treatment

Studies show that insulin can promote cancer growth and reduce chemotherapy effectiveness. Because fasting lowers insulin, researchers wanted to see whether changes in eating habits could help chemotherapy work better.

How the Study Worked

To improve the effectiveness of chemotherapy in advanced (Stage III or IV) HGSOC. They all received three rounds of chemotherapy before surgery.

The patients were split into two groups:

• The Regular Diet Group (18 patients): Ate their normal meals throughout treatment.
• The Fasting Group (18 patients): Fasted for 36 hours before and 24 hours after each chemotherapy session.

In this study, “fasting” did not mean avoiding all food and drink. Patients in the fasting group could have as much water and herbal tea as they wanted, up to two liters of vegetable juice, and small amounts of light vegetable broth. They kept their daily intake under 350 calories during fasting. Between chemotherapy cycles, they ate their usual diet.

What the Researchers Found

The results from this small study were promising:

• Much Lower Insulin: After three rounds of chemotherapy, insulin levels dropped in the fasting group. In the group that ate normally, insulin levels went up.
• Better Tumor Response: Nearly 60 percent of patients in the fasting group achieved a complete or near-complete response to chemotherapy before surgery, indicating their tumors shrank significantly. Among patients who ate normally, fewer than one in five had this result.
• More Time Cancer-Free: Early results suggest that patients who fasted remained cancer-free for an average of 38 months (just over three years), compared with 24 months (two years) for those who ate normally.
• It Was Safe and Manageable: Everyone in the fasting group finished their treatment. Side effects, such as low blood cell counts, were similar in both groups, so fasting did not worsen chemotherapy side effects.

The Bottom Line & Next Steps

“While this is a small study, the findings are encouraging … and highlight a promising area of cancer research,” said Dr. Eleonora Teplinsky, an ASCO expert in gynecologic cancers.

Because this was a small pilot study with only 36 people, larger clinical trials are needed to confirm these benefits before doctors can recommend fasting for everyone.

Clinical Takeaways

These findings add to the growing interest in metabolic interventions as supportive strategies during cancer care. In this small pilot study, short-term fasting around chemotherapy was associated with lower insulin levels, improved tumor response rates, and longer progression-free survival in patients with advanced high-grade serous ovarian cancer.

Although the results are promising, the study included only 36 patients and should not yet change clinical practice. Oncology teams should continue to focus on nutritional assessment and individualized support care while monitoring ongoing research on fasting, fasting-mimicking diets, and other metabolic approaches that may enhance treatment response without increasing toxicity.

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