After the long hot summer, these are the warning signs of skin cancer you need to look out for that aren’t moles. Here’s what to do if you spot red, scaly patches: DR JUSTINE HEXTALL

After the hottest UK summer on record – which also saw the UV index reach 8, meaning exposed skin can burn in as little as 15 minutes – you might well be wondering about sun damage.

Most of us know it’s wise to seek advice if a mole changes colour, shape or size. But there are other skin signs to look for too – for instance, an area that’s crusting, bleeding and just not healing could suggest a basal cell carcinoma (BCC), the most common kind of skin cancer.

Likewise, a warty, tender nodule – especially on sun-exposed places such as the ears, lips or scalp – could be a squamous cell carcinoma (SCC).

There is, however, a less well-known sign on my checklist, which I go through as a consultant dermatologist.

And that’s patches of red, scaling, sometimes rough skin on sun-exposed sites. This can represent sun damage – and in some cases pre-cancerous changes.

So after checking for skin cancer, I always check patients for evidence of significant sun damage.

These are areas of skin where cells may have already been altered by chronic UV exposure, so that the whole area – not just individual spots – is at higher risk of pre-cancerous and cancerous cells. We call this ‘field cancerisation’.

In other words, this kind of sun damage is not solely cosmetic, and there’s growing evidence that treating it can reduce the risk of going on to develop skin cancer. (Although having said it’s not a cosmetic issue, the same treatments that can prevent skin cancer can also improve the skin’s appearance and have an anti-ageing effect.)

Specifically, I look for dry, red patches called actinic keratoses (AKs). Sometimes these are small spots, but larger joined-up lesions can be a few centimetres in diameter. They may feel slightly warty and may be mildly tender. There may also be speckling with darker and lighter areas of skin, typically on the scalp, face, neck and chest.

AKs are pre-cancerous in the sense that they are cells that have begun to be abnormal but still only reside on the top layer of skin. They can then develop into SCC, the second most common type of skin cancer, which is fast-growing and affects the outer layer of skin (BCC is different and does not start as an AK, instead residing in a lower layer of skin, growing slowly there).

If I see an AK, I generally use my cryotherapy gun (using liquid nitrogen) to freeze it off.

But as well as these obviously thickened, warty spots or patches, I know not to ignore the subclinical damage you cannot see.

In fact, these subtler areas of sun damage may be just as important, and this is why clinicians like me are now treating the skin around obvious AKs – using prescription creams or light treatments to the whole area to make sure we don’t miss other subtle lesions – treating the entire face or scalp area, for example. 

There was an interesting study published in the British Journal of Dermatology in 2018 that suggested the most common AKs associated with invasive SCC (‘invasive’ means it’s moved into the deeper layers) were in fact the innocuous subclinical ones that are often overlooked – not the more obvious thickened ones that we freeze.

The researchers examined the tissue around invasive SCCs and found that, more often than not, the AKs bordering the cancer had abnormal cells deeper in the skin and as such were only mildly abnormal-looking and did not have the visibly severe changes you would expect or treat.

This is why treating the whole field of sun damage – ie the entire face – matters, and not just the lesions that you see, if we’re going to catch the damaged cells that are more likely to lead to SCC.

Yet this, unfortunately, is not done enough in the UK, in my opinion. Although guidelines in Australia and the US recommend ‘field treatment’, the National Institute for Health and Care Excellence (NICE) only suggests that we ‘consider’ it.

There is a clear preventative benefit in reducing the risk of SCC – but we don’t do it. So I would say to anyone who has signs of widespread sun damage, as described above – especially with a history of SCC – ask your skin specialist about possible field treatment.

One of the most effective and least expensive ways to treat the whole field is with a chemotherapy cream called 5-fluorouracil (5-FU).

This is usually applied up to twice a day to the area for four weeks. It works by poisoning fast-dividing cells, and as the sun-damaged cells turn over more quickly they are targeted preferentially.

The difficulty is, to be effective, the 5-FU cream has to be continued until the whole area is red and crusty – and this is painful as well as unsightly.

Understandably, people often feel they can’t socialise and, in many cases, even go into work with their skin looking like that.

However, there’s a newer approach combining 5-FU with a vitamin D (in the form of calcipotriol ointment) that seems to reduce the treatment time to as little as four days for the face and seven days for the body.

Along with the blunt instrument of the 5-FU, the vitamin D seems to trigger the skin to release a distress signal that recruits T-cells, a type of immune cell that attacks the abnormal cells. Essentially, it trains the immune system to recognise these damaged cells.

What is especially intriguing is that researchers believe these primed immune cells stay around, patrolling the area to mop up any newly forming mutated cells.

A study that first tested this approach, by researchers at Washington University School of Medicine in 2017, compared 5-FU and a placebo (Vaseline) versus 5-FU and topical vitamin D in 130 patients who had a history of skin cancers (SCC or BCC).

A follow-up study published in 2019 showed that 28 per cent of the 5-FU with placebo group went on to develop facial SCC within the next three years, compared with just 7 per cent in the 5-FU with vitamin D group.

Although this combined approach is not yet approved on the NHS for preventing SCCs, dermatologists can offer it ‘off-label’ (meaning use that’s not what the drugs were originally licensed for). Trials are ongoing and, once there’s more data, it may be considered for approval by NICE.

Another treatment I use for patients is daylight PDT (photodynamic therapy), where we apply a light-sensitising cream (containing aminolevulinate, ALA, or a version known MAL).

This is absorbed primarily by abnormal cells, and when the skin is then exposed to a red light or daylight (or artificial daylight, in winter months), the abnormal cells are killed off.

As well as reducing the risk of SCC, daylight PDT has been shown to have significant cosmetic benefits – dry, rough patches with an uneven skin tone reflect light badly, and the skin is usually perceived as looking older.

A study published last year showed this treatment not only reduced sun damage but also improved skin texture – tackling roughness, mottled pigmentation, and reducing thread veins and fine lines with both the patients (81.3 per cent) and the researchers (83.6 per cent) reporting outcomes as good or very good.

Combining this with fractional laser (which creates micro-channels in the skin) may also allow deeper penetration of the photosensitising gel to enhance results.

Finally, there’s one additional benefit I’ve noticed in people who have field treatment for sun damage: a complete change in sun behaviour. Suddenly, the lifelong golfer starts to wear SPF 50 and a hat!

I think psychologically that people often feel the damage from the sun is already done, so why bother? But once someone sees the benefits, they seem to see it as a reset and want to maintain this fresher, clear skin.

Dr Justine Hextall is a consultant dermatologist at Tarrant Street Clinic in Arundel, West Sussex