A quest to develop a global photographic sun damage scale

A photographic sun damage scale
A photographic sun damage scale

Measuring sun damage is an essential part of skin cancer research and treatment. It is also highly subjective, which makes it difficult to determine just how effective a new agent or intervention may be.

Arizona Cancer Center member Naja E. McKenzie, PhD, RN, is trying to change that. She is working to develop a global photographic sun damage scale to help standardize the process.

“The whole idea of having a scale is to be able to generalize judgment,” she said. “Our goal with this is to have this be the way people define sun damage.”

When researchers around the world describe a patient with skin damage, they use a ranking system – 0 for no damage, 9 for the worst of the worst – in three clinical categories and give an overall score. While the system seems logical, there’s no way to know if researchers are talking apples to apples – if an 8 to someone in Copenhagen is the same as an 8 to someone in Tucson.

While photographic scales exist to measure sun damage on the face, chemoprevention of skin cancer studies tend to focus on the forearm to more easily allow for biopsies to determine whether using a test agent has improved sun damage.

“This study is important because as we develop more agents to look at chemoprevention or for cosmetic purposes, scales must be generated to measure for damage,” said Clara Curiel, MD, who holds the Alan and Janice Levin Family Endowed Chair for Excellence in Cancer Research and who participated in the study. “It is important to have a scale that you can refer to, to measure outcomes of the interventions.”

To develop the scale, Dr. McKenzie and her team took photographs of 48 subjects’ right and left forearms. Duplicate copies were made and five community dermatologists in addition to Dr. Curiel ranked 288 images. While the physicians’ answers agreed in 73 to 90 percent of the cases, there was some diversity in the results, which only reinforced the need for a standardized scale.

“A lot of that depends on who you see on a regular basis,” Dr. McKenzie said. “If you see a lot of older people who play a lot of golf, you’re likely to think less of a bad looking arm because you’ve seen worse.”

Based on the answers the dermatologists gave, Dr. McKenzie has created a scale using photographs to represent a typical example of each level of the scale. Dr. Curiel was impressed at the overall agreement in the first leg of the study, and thinks it could be increased even more if reviewers are first presented with the new photographic scale.

“We were able to prove that between five physicians you can reach reasonable agreement,” she said. “The next step is to pre-train people and then see how the correlation changes with the scale being taught up front.”

The study, published in Archives of Dermatology in January, has received some good feedback; one reviewer called it a “God-send,” Dr. McKenzie said. The study will now be replicated in Australia by researchers in the Pan-Pacific Skin Cancer Consortium, which comprises scientists from the Skin Cancer Institute and Queensland Institute of Medical Research.

However, it’s just a first step. There are many issues that need to be worked out before the photographic scale can be applied to research and clinical situations globally.

“On each continent we don’t have the same skin color,” Dr. McKenzie said. “That’s something we will be working on down the road. There are a lot of different populations out there where this would not work as it stands. It’s very preliminary, but the concept and the blueprint of how to go about doing it are there.”