Screening results
Both groups identified as having a history of skin cancer (surfers 41.4% vs swimmers 36.4%, respectively) and a family history of skin cancer (surfers 52.6% vs swimmers 43.6%). The majority of surfers and swimmers that experienced blistering sunburns as a child were significantly (P <0.05) more likely found to have at least one skin cancer (BCC, SCC, SCC in situ, MSC; 74.1% vs 69.0%) identified in this study than those who did not experience blistering sunburns as children. Surfers reported a significantly higher (+85.5%, P <.05) number of lesions of concern as compared to swimmers prior to the screening.
There was no difference (P >.05) in experience (years surfing or years swimming) between groups however, there was a significant relationship between surfing experience (yrs) and the number of skin cancers identified (r= 0.312, P <.001). There was no difference in surfing or swimming total exposure hours and the number of skin cancers (r=-0.126,; r=0.065, respectively). However, when groups were combined, there were more participants identified with skin cancers when investigating total aquatic activity exposure (Figure 1 (A), quartile 1 vs quartile 4). Likewise, with groups combined, there were more skin cancers identified with increased activity exposure (quartile 1 vs quartile 4, Figure 1 (B)).
Insert Figure 1 A and B approximately here
A total of 74 AKs were identified during the screening (surfers 59, swimmers 15) and 110 skin cancers (BCC, SCC, SCC in situ, MSC) (Table 3). A significantly (P <.005) greater number of surfers were identified with a skin lesion (PSC, NMSC, MSC) during the screening than swimmers (132 vs 52, respectively; OR 1.85, 95%CI 1.0 to 3.5). Surfers also had a higher number (P >.05) of AK and rate (per 100,000) compared to swimmers (50,862 vs 27,273 respectively, OR 2.76). Surfers also had a higher number of BCCs compared to swimmers (27,568 vs 18,181 respectively, OR 1.71). Conversely, swimmers had a higher rate of SCC in situ (20,6903 vs 40,000, OR 0.70). Surfers had a significantly (P <.05) higher number of SCCs and a higher rate of SCCs compared to swimmers (9,482 vs 7,272, OR 1.34). With regard to malignant melanomas, surfers had a higher rate as compared to the swimmers (5,172 vs 1,818, OR 2.95).
When compared to the Australian general population, surfers and swimmers had higher ORs, which includes BCCs (OR 17.9 and 11.8, respectively), SCCs (OR 9.2 and 7.0, respectively) and MSC (OR 96.7 and 34.0, respectively) (Table 4). .
A MANCOVA demonstrated statistically significant differences in skin cancer totals (total number of skin cancers, total AKs, BCCs, SCC, SCC in situ, melanoma) based upon history of skin cancer (F = 3.98, Pillai’s Trace = 1.40, P <.001) with history of skin cancer as a fixed factor and covariates of Fitzpatrick skin type and age. Adjusting the mean number of skin cancers observed for covariates (age and Fitzpatrick skin type), totals were higher for those with a history of skin cancer (mean with skin cancer history 7.24 vs. 3.95 with no skin cancer history, P =.012). A similar trend was observed for AKs (6.03 vs. 3.69, NS), total BCC (0.66 vs. 0.06, P =.001), total SCC in situ (0.50 vs. 0.101, P=.042), total melanoma (0.62 vs. 0.44, NS) and total SCC (0.04 vs -0.01, P =.024, with the negative mean value due to adjustment to the mean by covariates).
Most skin cancers in surfers were located on the face (28.0%) followed by the arm and back (12.1% each), whereas in swimmers, the majority of skin cancers were identified on the face (17.3%), followed by the arm and lower leg (15.4% each). The highest number of melanomas were identified in surfers (n=6) and mainly located on the face (n=2) and back (n=2). There was a single melanoma identified on the back in a swimmer. When the groups combined, the majority (42.9%) of melanomas were identified on the back in participants, followed by the face (28.6%) (Table 3).
A total of 110 samples were sent for histopathology, and all (100%) were confirmed positive as either NMSC (BCC, SCC, SCC in situ) or MSC.