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Dostarlimab A1503



Information leaflet on Dostarlimab


This leaflet provides information for patients having treatment with Dostarlimab.  The leaflet will explain what Dostarlimab is, when and how it is given.  It will also tell you about common side effects that you may experience.  Contact telephone numbers and details of how to obtain further information on Dostarlimab are given at the end of the leaflet.


What is Dostarlimab and why am I having it?

Dostarlimab is a treatment known as immunotherapy. It helps your immune system to attack and destroy cancer cells.  It is not a chemotherapy drug.


How often will I receive Dostarlimab?

For this treatment to be most effective, it is given at specific time intervals. These are known as treatment cycles.  It is usual to have a cycle of Dostarlimab once every 3 weeks for the first 4 treatments. This is followed by ongoing treatment once every 6 weeks.  Your doctor will discuss with you how often you will have your treatment and how long you will continue having the treatment.


How often will I see the specialist team?

You will need to be reviewed regularly, this will either be done face to face in the outpatient clinic or a telephone consultation.  At each outpatient clinic the medical team or specialist nurse will check how you are feeling and discuss any problems you may have.


You will have regular blood tests and we will check how you are feeling and discuss any problems you may have.  This is so we can check how the treatment is affecting you.  If your blood results are satisfactory, your treatment will be given.


How is Dostarlimab given?

Dostarlimab is given through a drip into a vein in the back of your hand or arm.


Where will my treatment be given?

The treatments will be given in the day case treatment areas at Velindre, in one of the outreach clinics or on the mobile unit.


How long will I be in the hospital?

Please allow 11/2 to 2 hours for your appointment. Please allow 30 minutes longer for your first visit.


Can I bring relatives and friends with me?


You are welcome to bring someone to stay with you during your treatment. Space is limited so there is not usually room for more than one person.  Treatment areas are not suitable for young children.




Reactions during the treatment

If you experience any of the following during the treatment please tell your nurse straight away:


  • Feeling hot and feverish and/or facial flushing
  • Facial swelling
  • Chills or shivering
  • Headache
  • Dizziness or faintness
  • Problems with breathing
  • Rash or itching
  • Feeling sick or vomiting


If any of these occur we will slow down or stop the Dostarlimab until you feel better.  The treatment can then start again, usually without any further problems.



What are the possible side effects?

Most of the side effects happen because Dostarlimab affects the immune system causing inflammation of other parts of the body such as the skin, the bowels and hormone producing glands. Most, if not all severe side effects can be controlled by the use of steroid medication immediately either as tablets or through a drip.  Hospital admission may sometimes become necessary, however, for severe immune related reactions.


Mostly side effects are mild and can be easily managed at home. But sometimes cancer drugs can have very serious side effects which rarely can be life threatening.It is important that if you have more severe side effects that you contact Velindre Cancer Centre. The telephone number is at the end of the leaflet.  Further details of when to contact Velindre are included in the individual side effects listed below.


If you are admitted to another hospital, you must inform the doctors and the nurses that you are receiving Dostarlimab.  It is possible you could be having an immune reaction and should be started on steroids. The doctors and nurses need to contact Velindre Cancer Centre for advice.  They can either telephone the telephone helpline or speak to your oncologist.


You will be given an alert card, please show this to the nurses or doctors if you are admitted to any hospital.


Effects on the bowels  


This treatment has been known to cause diarrhoea due to inflammation of the bowel. If you experience diarrhoea it is important that you drink plenty of fluids.

Please note:

If you have any of the symptoms below you must inform Velindre Cancer Centre immediately, the telephone numbers are at the end of the leaflet.


  • 4 or more bowel movements in 24 hours above what is normal for you.
  • if you have any problems with diarrhoea or an increase in bowel movements which lasts for more than 3 days.
  • If you have severe stomach pains
  • Or if you have blood or mucus in your bowel motions


There is a risk of inflammation of the bowel (colitis) or rupture of the bowel (perforation) in a small minority of patients.

Effects on the skin

Use a non-perfumed body wash and moisturising cream to help to prevent skin reactions.


You may have a rash which is dry and itchy and cause mild discomfort. For a small number of people this reaction may be more severe.  A severe rash would affect a large part of your body, may be painful and may become infected.

If you develop a severe rash you should contact the treatment helpline; the number is at the end of the leaflet.


Effects on your hormone glands

Dostarlimab can cause inflammation of the glands that produce hormones. Hormones are chemicals that control many of the body’s functions. Symptoms will vary depending on which glands are affected.


It is important to contact Velindre cancer Centre if you have the following which may be a results of changes to hormones:

  •  a headache that will not go away
  •  nausea and vomiting
  •  severe mood swings and/or depression.
  •  severe tiredness (mild to moderate tiredness is  common with Dostarlimab)
  • if you have a noticeable increase in energy levels or restlessness.
  • if you feel forgetful and/or confused
  • sensitivity to heat or sweating
  • weight changes
  • difficulty sleeping


Effects on the liver


This is rare, but if you are affected you may feel more tired than usual and may also feel sick or vomit.  Your doctor will give you anti sickness medicine to take. 

Please contact Velindre Cancer Centre if you vomit more than once in 24 hours despite taking anti sickness medication.


More severe effects on the liver are very rare but can be very serious so you should contact Velindre Cancer Centre if:


  • If you have yellowing of your skin and the whites of your eyes.
  • If you have darker urine than normal.
  • If you have unusual bruising or bleeding
  • If you have pale stools
  • Pain in the upper right side of your tummy/abdomen


Shortness of breath or breathing problems

 If you notice a new problem with shortness of breath or a persistent cough ring the treatment helpline immediately. You will also be monitored at regular clinic visits for signs of inflammation of the lungs.


Tiredness and fatigue

Dostarlimab can make you feel more tired than usual.  It is important to listen to your body and rest if you need to, but carry out your normal activities if you feel able.  Some people find it beneficial to take gentle exercise as well as taking rest.  If you are sleeping more than 50% during the daytime you need to contact Velindre Cancer Centre on the number at the end of the leaflet.

Loss of appetite and nausea

You may experience a loss of appetite and some people may feel sick whilst receiving Dostarlimab but this can usually be well controlled with anti-sickness medication.  If you are sick more than once in 24 hours despite taking regular anti-sickness medicine, you should contact Velindre Cancer Centre for advice.  The telephone number is at the end of the leaflet.


Joint or muscle pains

Some patients may experience muscle or joint pain.   If you already have painkillers at home you may find they relieve the pain.  If this does not work please contact Velindre Cancer Centre.  The telephone number is at the end of the leaflet.


Other possible side effects:

You may have these additional side effects, if so please contact Velindre Cancer Centre:


  • Increased frequency of passing urine and/or thirst.
  • Dizziness or light headedness.
  • Decreased urine output.
  • Blurred, double or altered vision or red sore eyes.
  • Severe headaches, drowsiness, confusion, stiff neck or back.
  • Reduced sensation or numbness to hands and feet



Blood clots

A diagnosis of cancer can increase your risk of developing a blood clot (thrombosis), and having cancer treatment may increase this risk further.  It is important to tell your doctor immediately if you have symptoms such as pain, redness and swelling in your leg, or breathlessness and chest pain. 


Blood clots can be very serious.  However, most clots can usually be successfully treated with drugs to thin the blood.  Your doctor or nurse can give you more information


Other information

It is important you do not become pregnant, breastfeed or father a child whilst having Dostarlimab treatment and use contraception for at least 4 months after treatment has completed.


Side effects may continue or first start 12 – 18 months after treatment.  If you have any side effects contact the treatment helpline. If you are admitted to hospital or see your GP during this period, inform the doctor you have had Dostarlimab, an immune therapy and give them your alert card.


Manufacturer’s patient information leaflets

Velindre leaflets provide information about very common and commonly reported side-effects (we are unable to list all of the common side effects), for more information regarding these and the less common side-effects please refer to the manufacturers patient information leaflets, obtained from Velindre pharmacy and/or on the internet at Sometimes patients may find these leaflets difficult to read however. Please ask if you would like a copy from your doctor or from Velindre pharmacy




Contact telephone numbers



Velindre Cancer Centre          029 2061 5888

If you are unwell at home and need immediate attention at any time of the day or night ask for the treatment helpline



Pharmacy department            029 2061 5888 ext 6223

Monday – Friday 9am – 5pm for queries about your medicines


Macmillan freephone Helpline       0808 808 0000

7 days a week 8am – 8pm for general queries on cancer


Tenovus freephone                       0808 808 1010

cancer helpline

7 days a week 8am – 8pm for general queries on cancer





This leaflet was written by health professionals.  The information contained in this leaflet is evidence based.  The leaflet has been approved by doctors, nurses, pharmacists and patients.  It is reviewed and updated every 2 years.


Prepared February 2022