Short-Term Fasting Around Chemotherapy May Improve Treatment Response in Ovarian Cancer

Short-term fasting before and after chemotherapy reduced insulin levels and improved progression-free survival in patients with high-grade serous ovarian cancer, according to a pilot randomized trial presented at the 2026 ASCO Annual Meeting. The study found patients in the fasting group had a median progression-free survival of 38 months, compared to 24 months for those on a free diet.

Lead author Claudia Marchetti, MD, of the Fondazione Policlinico Universitario Agostino Gemelli IRCCS in Rome, Italy, stated during a press briefing that advanced ovarian cancer patients still face poor outcomes. Marchetti said this creates an urgent need for safe, low-cost strategies to enhance treatment efficacy.

How does short-term fasting impact chemotherapy response?

Insulin may support cancer growth and reduce how well chemotherapy works, according to the study authors. The trial tested whether fasting could improve metabolic parameters and treatment response in patients receiving carboplatin- and paclitaxel-based neoadjuvant chemotherapy.

After three chemotherapy cycles, insulin levels in the free-diet group increased by 9.76 µIU/mL. In contrast, insulin levels in the short-term fasting group decreased by 1.12 µIU/mL, according to the trial results (P= .01).

Translational analyses indicated lower levels of immunosuppressive granulocyte and monocyte subsets in the fasting group. Investigators suggested these immune changes may make the chemotherapy response more favorable.

Did You Know? A ketogenic diet arm was initially planned for the study but was closed early due to low compliance and preclinical data suggesting such a diet may promote tumor growth.

What were the specific fasting requirements for patients?

The protocol defined short-term fasting as a period starting 36 hours before chemotherapy and ending 24 hours after the cycle finished. During this window, patients were limited to a maximum daily intake of 350 kcal.

Permitted intake included unrestricted water and herbal tea, up to 2 liters of vegetable juice, and small amounts of light vegetable broth. Patients returned to regular eating habits between chemotherapy sessions.

Eligible participants had newly diagnosed advanced high-grade serous ovarian cancer and a body mass index of at least 19 kg/m². The study excluded patients with diabetes mellitus, malnutrition, eating disorders, or food allergies.

What clinical outcomes did the trial observe?

The fasting group showed a significantly higher pathologic response at interval cytoreductive surgery. A chemotherapy response score of 3, indicating a complete or near-complete response, occurred in 58.8% of fasting patients compared to 17.6% of those on a free diet (P = .03).

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Researchers also found a link between insulin and surgery eligibility. Patients who did not undergo interval cytoreductive surgery after three cycles saw a greater increase in insulin levels (11.46 µIU/mL) than those who did (1.35 µIU/mL), according to the data (P = .033).

The investigators reported no relevant differences in chemotherapy toxicity between the two groups. This suggests the fasting protocol was feasible and well tolerated by the participants.

Expert Insight: Samantha Carter notes that the significance of this trial lies in the contrast between the intervention’s simplicity and its potential impact. While most oncology breakthroughs involve expensive new drugs, this approach relies on a metabolic shift that could be implemented globally without significant financial barriers.

What happens next for fasting research in cancer?

Eleonora Teplinsky, MD, FASCO, Head of Breast and Gynecologic Medical Oncology at Valley-Mount Sinai Comprehensive Cancer Care, said the findings are encouraging and support earlier data. Teplinsky stated that larger clinical trials are now needed to build on these results.

Eric J. Small, MD, FASCO, 2025-2026 ASCO President, emphasized that the study demonstrated both short-term biologic effects on the immune environment and a measurable clinical impact. Small noted the intervention’s potential to be implemented anywhere in the world.

The authors indicated that these findings provide a rationale for larger multicenter randomized studies and longer follow-up periods. Such steps may validate whether short-term fasting consistently improves outcomes for ovarian cancer patients.

Frequently Asked Questions

What was the specific fasting window used in the study?
Patients fasted from 36 hours before chemotherapy until 24 hours after the end of each chemotherapy cycle.

What were the survival differences between the two groups?
The median progression-free survival was 38 months for the short-term fasting arm compared to 24 months for the free-diet arm.

Did fasting increase the toxicity of the chemotherapy?
No, investigators reported no relevant differences in chemotherapy toxicity between the fasting group and the free-diet group.

Do you believe simple lifestyle interventions like fasting will become a standard part of chemotherapy protocols?