Field Therapy for Solar Keratoses
Field Therapy is treatment of a whole area of skin in order to eliminate Solar Keratoses.
5 different compounds can be applied to the surface of the skin for Field Therapy. They work by 5 completely different mechanisms to kill solar keratosis cells. The main differences are in the following table. Below is detail about side effects and how they are applied.
No field therapy is covered by the PBS. They are all private prescriptions.
|Time to complete application
|Time start to normal again
|3 weeks on average
|4 weeks on average
|28, maybe twice
|5 weeks, maybe twice
|$50 for 20g
|$135 1 treatment
|$100 1 treatment
The compounds are all similarly effective. One important difference is that the application of Picato and Daylight PDT is completed before the maximum effects appear. With the slower acting compounds you can “titrate” the application until the appropriate response is achieved. But there’s the trade-off of having the inflammation for much longer.
All the treatments cause inflammation of normal cells but kill the cells of solar keratosis because chemicals penetrate their abnormal cell walls 10 times faster and being mutant they are less able to repair the damage.
Efudix is best used in winter because sunlight increases the reaction without making it work better.
Aldara may rarely cause a flare of an autoimmune disease (but there is no evidence that it can initiate a new autoimmune disease).
It is a good idea to return for review every two weeks or so during the treatment and a month after completion of the treatment. If it’s only to check progress, these consultations will be bulk billed.
Efudix (5-fluorouracil) throws a spanner in the works of DNA because it is altered uracil which is one of the bases that make the DNA code. It is used as chemotherapy for some internal cancers.
The maximum area you can treat at once is 500 square cms. So you could treat both hands and forearms at once or your whole face. Generally it is a good idea to treat a smaller area though such as forehead or cheeks and nose, and probably only one hand and forearm, because it can get quite sore towards the end of treatment.
People react differently to Efudix. The plan is to use it for 1 to 4 weeks, twice a day, until there is sufficient reaction. The amount of redness indicates that the efudix has done its work.
Exposure to sunlight while using efudix causes more inflammation (without making it work better) so use sunscreen and a hat and avoid the sun during treatment.
Efudix or the preservative may cause dermatitis which will be apparent as a more even redness over the whole area of application, not just redness of the solar keratoses.
Sometimes people experience fever, nausea, diarrhoea, headache or mouth ulcers. This is less likely if you treat a small area at one time.
Approximately 8% of people are thought to have partial dihydropyrimidine dehydrogenase deficiency. Their cells don’t inactivate the efudix as quickly as other people so they get a stronger reaction. Severe reactions are extremely rare with skin administration but do occur.
Efudix should never be used during pregnancy as it can cause major malformations in the baby.
HOW TO APPLY IT:
- Apply Efudix thinly to the site twice a day. Wash it off your fingers thoroughly afterwards.
- Don’t wash the site of application for an hour. After that it matters much less if you wash or rub the ointment off.
- Inflammation will increase and the lesions being targetted will begin to get “erosion”, which means they will ooze and get crusty, after 1 to 4 weeks. That is when Efudix has done its work and you can stop using it. Things heal up quickly after that.
- Soreness is minimised by applying moisturiser frequently. Steroid cream may also reduce the soreness but must only be used for a few days.
Aldara stimulates the immune cells at the site, so causes inflammation. Some of these cells kill mutated skin cells. Their activity seems to be increased by aldara, resulting in elimination of abnormal cells that the immune system was tolerating before.
Apply aldara by puncturing a sachet and using it as a squeeze tube. Keep the sachet in a closed jar so it doesn’t dry out. You can then get several days’ use out of one sachet. Apply aldara to the treatment area 3 days per week for 4 weeks. It may be necessary to change the frequency of application depending on the response. After application don’t wash the area for at least an hour. You can still use sunscreen and makeup on the treated area, just apply it after the aldara dries.
If the reaction becomes too painful or annoying, it is ok to stop aldara for a few days then start after the reaction has settled a bit. You don’t have to make up for these days by extending the 4 weeks.
Sometimes a second period of 4 weeks is required, after a break of 4 weeks.
Aldara can cause mild flu like symptoms, even diarrhoea and muscle pain. These symptoms may resolve with continued use, and will resolve after stopping the treatment. If you have an autoimmune disease, there is a possibility that aldara may trigger a flare up of that. There is no evidence that aldara can initiate an autoimmune disease.
Rarely aldara can cause an extreme response, with painful inflammation within a few days of commencement. If you are finding the response too much at any time, stop applying the aldara, photograph the reaction at its worst and see Dr Chaffey (or another doctor) as soon as possible.
Solaraze is Voltaren (diclofenac, an antiinflammatory) in a hyaluronic acid vehicle “which is designed to keep the drug in the epidermis and superficial dermis” rather than deeper absorption*.
Solar keratoses were found to have high levels of prostaglandins. Diclofenac blocks prostaglandin production, so it was tried for treatment of solar keratoses and found to be effective. We don’t know exactly how it works.
Solaraze is quite effective if used for 90 days. Only about 60% as effective if used for 60 days.
Itchy, dry skin is the only significant side effect. Inflammation is much milder than with Efudix or Aldara because Solaraze works more slolwy. Whereas we aim for sufficient evidence of damage to the solar keratoses with Efudix and Aldara, with Solaraze the solar keratoses become less inflamed and we just aim for 90 days of treatment.
Solaraze shouldn’t be used in pregnancy (especially 3rd trimester when it can cause Patent Ductus Arteriosus) or while breastfeeding and may cause an allergic reaction in someone allergic to aspirin.
* About 10% of the voltaren is absorbed systemically, nevertheless and Hyaluronic Acid is a monster molecule that will stay on the skin surface. It is a component of many dermal fillers used in cosmetic surgery. So how does it influence the depth of absorption of Voltaren? Solaraze costs $50 for 25g versus $6.50 for 20g Voltaren Gel.
Picato is Ingenol Mebutate purified from milkweed (Euphorbia peplus). It was developed by Australian Dr Jim Aylward with the Queensland Institute of Medical Research.
Picato causes cell death, by an unknown mechanism.
The advantage of Picato is its short period of application. The skin becomes inflamed and is back to normal after about 10 days usually. The effects occur after the application is completed, however, so you can’t adjust the dose depending on how your skin responds, as you can with slower acting compounds.
Apply 0.015% gel to the face or scalp once daily for 3 days. 0.05% gel for 2 days is for use on the body or limbs.
Don’t use on irritated skin or skin that has not healed from other treatments or surgery. Dont apply right after taking a shower or less than 2 hours before bedtime. After spreading evenly on the treatment area, let the medication dry for 15 minutes. Wash your hands right away with soap and water. Avoid getting the drug on other areas, including near the eyes, lips, or mouth. If you accidentally get ingenol in your eyes, flush them well with large amounts of water and get medical care right away. Avoid washing and touching the treated area, or doing activities that cause excessive sweating, for 6 hours after application. After this time, you may wash the area with a mild soap. Even after washing your hands, the medication can remain on your hands and be transferred to your skin or eyes. Care should be taken when applying make-up or inserting contact lenses.
The skin treated will become inflamed, painful and swollen. Sometimes nose, throat and eye discomfort occur and sometimes headache.
Daylight Photodynamic Therapy
5-ALA is 5-aminolevulinic acid which is converted to protoporphyrin IX by enzymes inside cells. Certain wavelengths of visible light are absorbed by protoporphyrin IX delivering a quantum of energy that drives a chemical change producing reactive forms of oxygen that react with and destroy components of the cell. The outcome is selective destruction of the abnormal cells that make solar keratosis.
PDT using special lights has been used by dermatologists to treat a range of conditions in common practice since the 1980s. The principles of this therapy were discovered in 1902.
PDT using daylight for solar keratoses has been developed in the last decade. It has the advantage over conventional PDT of being much less painful. If it becomes painful the patient can withdraw from bright light which stops the reaction and the pain.
PDT has the advantage of involving the shortest period of inflammation. It is only effective on the face and scalp, however.
5-ALA PDT is almost as effective as efudix which is the commonest and longest standing field therapy for solar keratoses.
For PDT under LED lighting, 13000 lumens on the skin surface is required but you don’t need sunscreen or have to brave the elements. In particular, if the ambient temperature is 10 degrees Centigrade or lower, PDT doesn’t work.
What to Expect
The skin will become red and sore within 24 hours and gets to its worst redness and scaliness at about 48 hours. Most of the redness will resolve by 7 days. You will probably feel you can appear in public on about day 6. Sometimes it takes 3 months for all of the redness to resolve completely.
How it is Applied
If you are going to use outdoor light, sunscreen will be applied as the first step.
Some thickened skin may need to be thinned by the doctor. Some lesions may need the application of salicylic acid ointment for 2 weeks beforehand to thin thickened skin.
Off Label Indication
5-ALA is approved for PDT by the FDA in the USA as Levulan. In Australia and the UK however, it is methyl-aminolevulinic acid that is approved for PDT marketed as Metvix. The use of 5-ALA for daylight PDT is therefore an off-label use in Australia. We are required to have a signed consent form to acknowledge that you are aware it is an off-label use. If you would prefer, we can instead use Metvix for daylight PDT but it costs $400 rather than $100 for a 2g tube.
5-ALA is available for application on the following days.
At Hazelbrook General Practice it can be applied on Fridays if booked a week before
At North Sydney General Practice it can be applied on Thursdays
The cost of 5-ALA is $100 and the associated consultations will be bulk billed.