Medical Oncologist
Bevacizumab (Avastin)
How Long Does Bevacizumab — Take to Work?
Bevacizumab works differently from chemotherapy. It cuts off the blood supply to tumours rather than attacking cancer cells directly, which means early benefit usually looks like stability on a scan — not dramatic shrinkage. Your first formal response assessment is typically after two to three cycles of treatment.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- Acts on blood vessels, not cancer cells directly — Bevacizumab starves tumours of new blood supply, so the effect builds over weeks rather than days.
- First scan usually after 2 to 3 cycles — That is roughly weeks 6 to 9 for most three-weekly regimens. Ask your team when yours is booked.
- Stable disease is often a success — If tumour growth has stopped, the treatment is working as intended — even without visible shrinkage.
- Symptoms may settle before the scan — Some people notice less pain or breathlessness before imaging confirms any change.
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Bevacizumab does not shrink tumours the way chemotherapy does. It works by cutting off the tumour's blood supply. The first sign it is working is often stable disease on a scan — no growth. That first scan is usually scheduled after two to three cycles, roughly weeks 6 to 9.
How does bevacizumab work, and why does response take time?
Bevacizumab targets a protein called VEGF, which tumours use to grow new blood vessels. By blocking VEGF, the drug aims to cut off the tumour's supply of oxygen and nutrients.
This is a slower process than chemotherapy, which attacks dividing cells more directly. Anti-angiogenic drugs like bevacizumab are designed to contain tumour growth rather than cause rapid shrinkage.
Scans done too early — before two full cycles — often cannot give a reliable picture of whether the drug is having an effect.
When will your first scan be, and what does it measure?
Formal response assessment — usually a CT scan — is typically planned after two to three cycles, in line with NCCN and ASCO guidance. For a three-weekly regimen, that is around weeks 6 to 9. For a two-weekly regimen, it is often around weeks 4 to 6.
Your team will schedule this scan from the start of treatment. If you are unsure when yours is, ask at your next infusion appointment.
The scan is measured against your baseline scan taken before treatment began. Your oncologist will explain the result and what it means for the next phase of your plan.
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Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
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Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
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Dr. Mohammed Imran
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Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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What should you expect at each stage?
Day 1: First infusion
Bevacizumab is given by drip in a day-care setting. The first infusion typically takes longer than later ones as the team monitors you for reactions. Most people go home the same day.
Weeks 1 to 6: Between infusions
The drug is working at the molecular level even when you cannot feel it. Some people notice symptoms settling — less pain, less breathlessness, or less swelling. Report any new symptom to your team, even one that seems unrelated to your cancer.
Weeks 6 to 9: First response scan
A CT scan is compared with your baseline. Your oncologist will tell you whether the disease has grown, stayed stable, or shrunk. This is the first reliable answer to whether bevacizumab is working for your tumour.
After the scan: Plan review
If disease is stable or shrinking, treatment usually continues with regular scans every two to three months. If the disease has grown, your oncologist will discuss what options are available next.
What should you keep track of while you wait?
- Ask on day one when your first response scan is scheduled — leave with a date.
- Keep a brief daily note of your main symptoms and whether they are changing.
- Report any new symptom to your team, even one that seems unrelated to your cancer.
- Do not delay or skip infusions without speaking to your oncologist first.
- Tell your team about every supplement, herbal remedy, or other medicine you are taking.
- If you feel better before the scan, tell your team — it is useful information for them.
What does it mean if your scan shows stable disease?
Stable disease — where the tumour has neither grown nor clearly shrunk — is a meaningful clinical result for an anti-angiogenic drug. ASCO and NCCN guidance recognises stable disease as a valid treatment response, not a failure.
Containing the disease and preventing growth is the intended goal of bevacizumab in many patients, not dramatic shrinkage.
Your oncologist will explain what the result means for your specific situation and what the plan is from that point.
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Common questions
Frequently asked questions
How many cycles before I know if bevacizumab is working?
Two to three cycles is the point at which your team can reliably assess whether bevacizumab is having an effect. A scan taken before that is often too early to show a meaningful difference from your baseline. The exact number of weeks depends on whether your regimen is two-weekly or three-weekly — ask your oncologist when your specific scan is planned.
Does bevacizumab shrink tumours?
It can, but shrinkage is not the primary goal and is not the main way your team measures success. Bevacizumab is designed to stop tumours from growing new blood vessels, so the target outcome is usually containment rather than shrinkage. Where shrinkage is seen, it often occurs alongside chemotherapy given at the same time, and becomes clearer after several cycles.
Can I feel bevacizumab working before the scan?
Some people do — a reduction in pain, breathlessness, or swelling can be an early sign of benefit, and it is worth reporting to your team. But a symptom improvement does not replace the scan, and feeling no different in the first few weeks does not mean the drug is failing. The scan gives information that symptoms alone cannot provide.
What happens if the first scan shows the disease has grown?
Your oncologist will explain the result and what options are available. Progression on bevacizumab does not mean there are no further choices — your plan may change to a different drug or regimen. Some patients continue on bevacizumab in specific circumstances even after progression; your oncologist will explain whether that applies to you. The conversation about next steps should happen within a few days of the scan result.
How long will I stay on bevacizumab if it is working?
There is no fixed duration that applies to everyone. Treatment continues for as long as the disease is stable or responding and the side effects are manageable. NCCN and ESMO guidance supports continuing anti-angiogenic therapy until progression or unacceptable toxicity in regimens where it forms part of the standard approach. Your oncologist will review the plan at each scan and discuss it with you.
Is it a bad sign if I feel no different after the first cycle?
Not at all. Bevacizumab works at the molecular level — cutting off blood supply to tumours — and this process does not produce symptoms you can feel. Many people who respond well feel no different in the early weeks of treatment. The scan at weeks 6 to 9 is the meaningful checkpoint, not how you feel after cycle one.