Medical Oncologist
Mutation-targeted treatment
ROS1-Positive Cancer: — A Rare Mutation with Targeted Treatment
ROS1 gene fusion is a rare mutation in lung cancer that matches to a specific class of oral targeted drugs. If your tumour carries this fusion, your treatment is built around it from day one.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- A rare but clearly actionable mutation — ROS1 fusion is found in a small proportion of non-small cell lung cancers, but it is one of the clearest targets in oncology for a matched drug.
- Oral treatment taken at home — ROS1 inhibitors are daily capsules or tablets — not infusions — taken at home without hospital admission.
- Brain spread changes drug choice — Some ROS1 inhibitors cross into the brain more effectively. Your oncologist will factor this into which drug is selected.
- Options if the first drug stops working — Resistance is manageable in some cases with a different agent, a clinical trial, or a move to another treatment approach.
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ROS1 gene fusion is a rare rearrangement found in a small proportion of non-small cell lung cancers. Oral drugs called ROS1 inhibitors target this mutation directly. NCCN and ASCO recommend an ROS1 inhibitor as first treatment for this mutation, and response rates in this group are among the highest seen in targeted lung cancer therapy.
What is ROS1-positive cancer and how is it treated?
ROS1 is a gene that, when it fuses to another gene by a chromosomal accident, produces an abnormal protein that tells cancer cells to grow and divide without stopping.
Targeted drugs called ROS1 inhibitors block this protein directly. They are taken as daily oral capsules or tablets at home and work specifically on tumour cells carrying the ROS1 fusion.
NCCN and ASCO recommend starting with an ROS1 inhibitor, not chemotherapy, as the first treatment for ROS1-positive non-small cell lung cancer.
Does it matter if the cancer has spread to the brain?
Yes, and it directly affects which drug your oncologist will recommend. Some ROS1 inhibitors cross the blood-brain barrier more effectively than others.
If brain spread is present at diagnosis, NCCN guidance specifically addresses drug choice for this situation. Your oncologist will prefer an agent with demonstrated intracranial activity.
Brain metastases do not disqualify you from targeted therapy. They make the drug selection more specific, not less likely to help.
What do the medical terms on your report mean?
- ROS1 fusion
- A chromosomal change where the ROS1 gene joins with another gene, producing a protein that drives cancer cell growth. Also called a ROS1 rearrangement.
- ROS1 inhibitor
- A targeted oral drug that blocks the abnormal ROS1 fusion protein. Most are taken as daily capsules or tablets at home, without a hospital infusion.
- Next-generation sequencing (NGS)
- A laboratory test that reads many genes from your tumour tissue at once, including ROS1, in a single run. It is the preferred method for finding actionable mutations per NCCN and ESMO.
- FISH
- Fluorescence in situ hybridisation — a test that looks directly at chromosomal rearrangements including ROS1. Used in some centres alongside or instead of NGS.
- Intracranial activity
- The ability of a drug to cross from the bloodstream into the brain and work against cancer cells there. Relevant when choosing between ROS1 inhibitors if brain spread is present.
- Resistance
- When a cancer that initially responded to a targeted drug finds a molecular way around it and starts growing again. A repeat biopsy can sometimes identify the mechanism and open options for a change in treatment.
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Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
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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Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
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Radiation Oncologist
Radiation Oncologist
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Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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What happens from diagnosis to starting treatment?
Biopsy taken
Tumour tissue is collected, usually via bronchoscopy or a CT-guided needle. The preserved tissue is then sent for biomarker testing.
Biomarker panel ordered
Your oncologist sends the tissue for next-generation sequencing, which checks for ROS1 and many other actionable mutations in one test.
ROS1 fusion confirmed
The laboratory reports which partner gene ROS1 has fused with. Results usually take one to two weeks, depending on where testing is done.
Drug options discussed
Your oncologist explains which ROS1 inhibitors suit your situation, including whether brain spread is present and which agent covers both.
Oral treatment starts
You begin a daily capsule or tablet at home. No hospital admission is needed. Your team will tell you which side effects to watch for and when to call.
Response assessed
A CT scan or PET-CT is arranged after a period of treatment to see how the cancer has responded. Scans are then repeated at agreed intervals.
Which ROS1 inhibitors are used, and how are they different?
Crizotinib
Crizotinib was the first drug to receive approval for ROS1-positive non-small cell lung cancer and has been used in this setting for over a decade. It is taken as an oral capsule twice daily at home. It has strong systemic activity against ROS1-positive tumours but crosses into the brain less reliably than newer agents. NCCN lists it as an option primarily when brain metastases are not a concern at diagnosis. Commonly reported side effects include mild visual changes, nausea, lower limb swelling, and fatigue.
Entrectinib
Entrectinib is listed by NCCN as a preferred option for ROS1-positive non-small cell lung cancer, particularly when brain metastases are present at diagnosis. It is taken once daily as a capsule and crosses the blood-brain barrier more effectively than crizotinib. It also has activity against NTRK gene fusions, so a tumour carrying both markers may respond to a single drug. Commonly reported side effects include fatigue, dizziness, constipation, and gradual weight increase over time.
Lorlatinib
Lorlatinib was developed initially for ALK-positive lung cancer and has demonstrated meaningful activity in ROS1-positive disease, including strong penetration into the brain. NCCN includes it as an option in the ROS1-positive setting, particularly when other ROS1 inhibitors have stopped working or where brain control is the primary concern. Side effects your team will monitor include changes in cognition, altered mood, and elevated cholesterol levels in the blood — all manageable with awareness and regular review.
What happens if the first ROS1 inhibitor stops working?
Resistance to targeted drugs develops in most patients over time. When scans show the cancer growing again, your oncologist may arrange a repeat biopsy to identify the molecular reason. If the resistance pattern allows it, switching to a different ROS1 inhibitor is sometimes possible. In other cases, chemotherapy, immunotherapy, or a clinical trial specifically for this stage may be recommended. The right next step depends on your biomarker result at progression and which options are available to you at that point.
Did you know?
ROS1 gene fusions share structural similarities with ALK, another driver mutation in lung cancer. When ROS1 fusions were identified as actionable, a class of drugs already in clinical development for ALK could be tested against them rapidly.
Patients with ROS1-positive lung cancer benefited from years of prior clinical work on a closely related target — a rare case where molecular similarity shortened the path from discovery to approved treatment.
Source: NCCN Guidelines for Non-Small Cell Lung Cancer
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Common questions
Frequently asked questions
Is ROS1-positive cancer always lung cancer?
No. ROS1 gene fusions have been found in other cancer types including bile duct cancer, colorectal cancer, and some brain tumours. Entrectinib is approved for ROS1-positive solid tumours of any origin, not only lung cancer. However, ROS1 testing is most routinely done for non-small cell lung cancer because that is where the fusion is most commonly found. If ROS1 fusion is identified in a different cancer type, your oncologist will discuss whether a ROS1 inhibitor applies to your specific situation.
Do I still need chemotherapy if I have a ROS1 mutation?
For most patients with ROS1-positive non-small cell lung cancer, NCCN and ASCO recommend starting with an ROS1 inhibitor rather than chemotherapy. Chemotherapy may still be used if an ROS1 inhibitor stops working, if there is a clinical reason you cannot take a targeted drug, or if your tumour carries additional features that change the approach. Your oncologist will explain the planned sequence of treatments and the reasoning behind it at your consultation.
How long does a ROS1 inhibitor keep working?
There is no single answer that applies to everyone. Duration varies between individuals, between drugs, and with how the cancer behaves over time. NCCN and ASCO do not specify a fixed duration because individual variation is significant. What matters more than a population average is your individual response, which your team monitors with regular scans. When resistance develops, there are usually further options to discuss rather than a single endpoint in your care.
Is ROS1 testing available in India, and can I get a second opinion on the result?
NGS-based testing that includes ROS1 fusion analysis is available through specialist laboratories in India and is recommended by NCCN and ESMO for all patients with non-small cell lung cancer before starting treatment. Your oncologist will typically arrange testing from your existing biopsy tissue without a new procedure. If you want a second laboratory to confirm the result, make sure the test specifically includes ROS1 fusion testing — this is distinct from an ROS1 point mutation test, and the difference matters for treatment decisions.
Is ROS1-positive lung cancer treated at CION?
Yes. CION has centres across Telangana and Andhra Pradesh that support patients with ROS1-positive cancer through the full treatment pathway. Oral targeted therapy does not require an infusion, so clinic visits centre on monitoring, blood tests, and prescription review. PET-CT and other response-assessment imaging is coordinated with partner imaging centres rather than done at CION directly. CION does not provide CAR-T or cell therapy — if that becomes relevant for your situation, a referral would be arranged to a centre that does.
How much does ROS1 inhibitor treatment cost in India?
Cost varies considerably depending on which drug is selected, how long treatment continues, your insurance coverage, and whether you qualify for a patient assistance programme from the manufacturer. Indicative costs as of 2025-26 differ between the available agents. Ask your oncologist's team to connect you with a hospital social worker or patient access coordinator early in the process — some programmes substantially reduce or eliminate out-of-pocket cost for eligible patients, and this is not information that is always volunteered without asking.