Can Fasting Around Chemo Improve Ovarian Cancer Outcomes?

A few days of fasting around chemotherapy sessions may improve treatment response and outcomes for some patients with advanced ovarian cancer, a small phase 2 trial suggests.

The study, of 36 patients with stage III or IV high-grade ovarian cancer, found that those randomly assigned to fast for 36 hours before chemotherapy and 24 hours afterward had stronger pathologic responses to chemotherapy and longer progression-free survival than patients who ate normally during treatment.

The findings, reported at a press briefing ahead the American Society of Clinical Oncology (ASCO) 2026, hint at a straightforward measure to potentially improve patients’ outcomes.

The working theory is that short-term fasting boosts chemotherapy response by lowering insulin and IGF-1 levels, both of which are implicated in tumor growth and chemotherapy resistance, said study presenter Claudia Marchetti, MD, of Agostino Gemelli University in Rome, Italy.

Speaking at the briefing, ASCO President Eric Small, MD, of the University of California San Francisco, called the study “a great example of a very simple intervention that has benefit and can be undertaken and implemented anywhere in the world.”

“It’s not an expensive new drug,” he said, “and yet it has the potential to really have an impact on this cancer.”

Ovarian cancer affects more than 324,000 women worldwide each year and causes more than 206,000 deaths annually. Around 80% of patients are diagnosed at an advanced stage, and up to 60% receive neoadjuvant chemotherapy to reduce tumor size and facilitate surgery.

Despite advances in surgery and chemotherapy, patients with advanced disease still face poor outcomes. There is, Marchetti said, “an urgent need for safe, low-cost, and easily implementable strategies that can enhance treatment efficacy and improve patient prognosis.”

Given evidence on the role of insulin in tumor growth and chemotherapy response, her team hypothesized that short bouts of fasting around the time of treatment might have benefits.

To test that idea, the researchers recruited 36 patients with newly diagnosed stage III or IV high-grade serous ovarian carcinoma who were not candidates for primary cytoreduction. All were in good general health, with a mean age of 62 years.

All patients received 3 rounds of carboplatin and paclitaxel before surgery. Prior to starting chemotherapy, half were randomly assigned to fast for 36 hours before and 24 hours after chemotherapy, whereas the other half ate normally throughout treatment.

Patients in the fasting group consumed no more than 350 calories per day during the fasting window. They were allowed to have unrestricted water, herbal tea, limited vegetable juice, and small amounts of light vegetable broth. (A ketogenic diet group had initially been planned but was closed early because of poor patient compliance.)

The study met its primary endpoint of change in insulin levels during chemotherapy, Marchetti reported. Baseline insulin levels were comparable between the 2 groups, but after 3 rounds of chemotherapy, they’d dipped by an average of 1.12 µIU/mL in the fasting group and increased by 9.76 µIU/mL in the control group (P = .01).

Fasting also improved clinical outcomes. Specifically, Marchetti said, 59% of fasting patients achieved a chemotherapy response score of 3 — indicating complete or near-complete tumor response before surgery — compared with 17% of patients in the control group.

Median progression-free survival was significantly longer in the fasting group, at 38 vs 24 months.

Importantly, Marchetti said, the fasting protocol was feasible, well tolerated, and safe: All patients assigned to the fasting group completed treatment, and rates of chemotherapy-related toxicities were similar between the 2 groups.

Additional analyses shed more light on the possible mechanisms underlying the fasting group’s improved outcomes: The researchers found that those patients tended to have lower levels of circulating suppressor granulocyte and monocyte populations that have been linked to tumor immune escape, which suggests, Marchetti said, fasting may have set the stage for a “more favorable immune environment” during chemotherapy.

However, she cautioned that much more research is needed. Her team is planning a larger multicenter trial to validate the current findings, and longer-term follow-up is necessary to see whether fasting ultimately impacts patients’ survival, Marchetti said.

In a statement, Eleonora Teplinsky, MD, an ASCO expert in gynecologic cancers, said these early findings are “encouraging, support earlier data, and highlight a promising area of cancer research.”

But she, too, emphasized the need for larger clinical trials to build on the results.

The study had no commercial funding. Marchetti disclosed having relationships with Arquer Diagnostics, AstraZeneca, Clovis Oncology, and other companies. Small disclosed having relationships with Janssen, Johnson & Johnson, and others. Teplinsky had no disclosures.

A version of this article first appeared on Medscape.com.