The Utility of the SUNTRAC Tool in Predicting Skin Cancers in Renal Transplant Patients

ABSTRACT

This study evaluates the SUNTRAC tool in guiding initial skin cancer risk stratification among renal transplant patients in New Zealand. Higher retrospectively applied SUNTRAC grades in 219 patients were associated with higher incidence of skin cancer, supporting the tool's effectiveness in guiding initial skin cancer risk stratification in this population.

1. Introduction

Solid organ transplantation patients are at increased risk of skin cancer due to improved survival and prolonged immunosuppressive therapy [1]. Up to 40%–50% of Caucasian recipients in the West, and 70%–80% in Australasia, develop non‐melanoma skin cancer within 20 years of transplant. Fair‐skinned recipients face a 65‐ to 250‐fold higher risk of squamous cell carcinoma (SCC) than the general population [1].

While Māori and Pacific populations have a lower incidence of non‐melanoma skin cancers, they experience more aggressive melanomas and poorer outcomes than Europeans [2]. Māori have a high incidence of chronic kidney disease and end‐stage renal disease, often secondary to diabetic nephropathy, glomerulonephritis and hypertensive renal disease, associated with lower socio‐economic status and access to health care [3]. Post‐transplant outcomes, including graft loss and mortality with a functioning kidney, are worse compared with non‐Māori [4], highlighting need for close follow‐up.

The Skin and Ultraviolet Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) is an online tool that stratifies organ transplant patients based on five risk factors; age ≥ 50 years, white race, male sex, thoracic organ transplantation and pre‐transplant skin cancer history [5]. The tool classifies patients into four risk groups (low, medium, high and very high), each with a recommended interval to first skin check (10 years, 2 years, 1 year and 6 months, respectively). The tool demonstrates strong prognostic discrimination in the Transplant Skin Cancer Network population study [6]. While the original SUNTRAC study excluded basal cell carcinomas (BCCs) given their low morbidity, we have included them, as a history of BCC is a risk factor for melanoma and non‐melanoma skin cancers [7, 8].

In the study region, renal transplant patients are routinely referred to Dermatology for skin cancer risk assessment and a full skin check in person or via teledermoscopy [9]. The teledermoscopy clinic or Virtual Lesion Clinic (VLC) is a nurse‐led service at which full‐body skin check and regional, close‐up and dermoscopy photographs of suspicious lesions are sent for remote diagnosis by a Health New Zealand Dermatologist. Until the results of this study were available, referrals included the date of transplantation, creatinine and immunosuppressive medications, without skin colour or skin cancer history.

This report summarises an audit of skin cancer surveillance in a New Zealand renal transplant cohort to assess the applicability of the SUNTRAC tool to the timeliness of initial dermatological review.

2. Main Text

2.1. Methods

We retrospectively analysed all renal transplant patients managed by Waikato, Rotorua and Gisborne renal services as of 1 February 2023. Data were collected from clinic records, teledermoscopy reports and histology results from public hospitals and community laboratories. Patient demographics, first transplant dates, referral and skin check dates and histology outcomes were recorded. Exclusion criteria included being age < 18 at transplant or if there were significant missing data. Patients were retrospectively assigned SUNTRAC scores. Fitzpatrick skin type had often been recorded and was used as a surrogate for ‘White race’, as we could not determine race retrospectively, given that ethnicity is self‐identified and does not correlate with skin complexion. We compared SUNTRAC score and time to first histology, both including and excluding BCCs. Statistical analysis included non‐parametric tests (Kruskal–Wallis, chi‐squared, Fisher's exact test) and categorical comparisons.

2.2. Results

There were 228 total renal transplant patients, of which 9 were excluded according to the exclusion criteria, leaving 219 included in the study (Figure 1). Demographics are shown in Table 1.

FIGURE 1.

Study population.

TABLE 1.

Demographics of the study population (n = 219).

Variable	n	%
Age in years
18–30	35	16
31–50	95	43
51–70	86	39
70+	3	1
Sex
Male	131	60
Female	88	40
Ethnicity
NZ European	132	60
Māori	60	27
Asian	6	3
Indian	8	4
Pacific	10	5
African	1	0.5
Not specified	1	0.5
Fitzpatrick skin type
I–III (White)	90	41
IV–VI (not White)	39	18
Unspecified	90	41
Pre‐transplant cancer history
Yes	13	6
No	174	80
Unspecified	32	14
Current domicile
Waikato	169	78
Tairawhiti	19	9
Lakes	31	14

Abbreviation: NZ, New Zealand.

Of the 219 patients, 200 (91%) were referred or seen at least once, the latter implying referral despite missing referral data. Among these, 182 (83%) attended a skin check. Referral data were available for 177 patients, with a median time from transplant to referral of 106 days (IQR 1160 (32–1192 days)). Forty patients had their first skin check via the VLC, 68 attended at least once and 108 VLC appointments were included.

The median interval from transplant to first skin check was 320 days. The median time between referral and first skin check was 128 days (IQR 216 (40–256)), longer for those going directly to dermatology (436.5 days; IQR 1888.75 (144.25–2033)) versus VLC (128 days; IQR 216 (40–256)). New Zealand European patients had the longest median wait time (437 days), though not statistically significant (p = 0.13). Māori had a shorter median time of 201 days but the greatest loss to follow‐up (48%), followed by Pacific patients (44%; p = 0.86). Applying SUNTRAC grade, loss to follow‐up was highest in the very high‐risk patients (50%, p = 0.30).

Skin cancer was confirmed by biopsy or excision in 45 patients (21%), of whom 44 were New Zealand European and one Asian. Non‐BCC skin cancer occurred in 29 patients within the study period. BCC was the most common first lesion (47%), followed by SCC (42%), both BCC and SCC (7%) and melanoma (4%). Further cancers developed during the study in 80% of patients. New Zealand European ethnicity was more often associated with skin cancer than other ethnicities (p < 0.001). Melanoma was diagnosed in five patients post‐transplant, and one patient had multiple primary melanomas. The median time to first positive histology was 1988 days (IQR 4054 (598–4530)). Excluding BCCs, the median was 2693 days (IQR 5098 (1259–6357)).

Sufficient data were obtained to assign a retrospective SUNTRAC grade for 125 patients: 21% (n = 39) low, 32% (n = 59) medium, 12% (n = 21) high and 3% (n = 6) very high. We could not determine skin colour for 57 patients (31%). Overall, 78% (97 patients) were seen earlier than recommended by SUNTRAC, including 95% of low‐risk and 66% of high‐risk patients (Table 2). Review of patients with more urgent SUNTRAC grades within recommended timeframes was less likely compared with less urgent grades (p = 0.02).

TABLE 2.

Positive histology compared to SUNTRAC grade (n = 182).

Low risk (n = 39)
First skin check before SUNTRAC recommended interval	37 (95%)
Positive histology	2 (5%)
Positive histology with BCCs excluded	2 (5%)
Median days to first histology (n = 2)	4097
Median days to first histology with BCCs excluded (n = 2)	4097
Medium risk (n = 59)
First skin check before SUNTRAC recommended interval	41 (69%)
Positive histology	19 (32%)
Positive histology with BCCs excluded	12 (20%)
Median days to first histology (n = 19)	2460
Median days to first histology with BCCs excluded (n = 12)	3592
High risk (n = 21)
First skin check before SUNTRAC recommended interval	15 (71%)
Positive histology	9 (43%)
Positive histology with BCCs excluded	3 (14%)
Median days to first histology (n = 9)	937
Median days to first histology with BCCs excluded (n = 3)	1589
Very high risk (n = 6)
First skin check before SUNTRAC recommended interval	4 (66%)
Positive histology (n = 4)	4 (66%)
Positive histology with BCCs excluded (n = 3)	3 (50%)
Median days to first histology (n = 4)	1390
Median days to first histology with BCCs excluded (n = 3)	1241
Not graded (n = 56)
Positive histology (n = 15, 27%)

Abbreviations: BCC, basal cell carcinoma; SCC, squamous cell carcinoma.

Positive histology rates increased with SUNTRAC risk: 66% in very high‐risk and 50% in high‐risk groups (Table 2). Higher SUNTRAC grade was statistically associated with the likelihood of positive histology (p = 0.0005). Medium, high and very high‐risk groups were significantly more likely to have skin cancer compared to the low risk (p = 0.0011, 0.0007, 0.0014 respectively), though not significantly different from each other p = 0.43 and 0.17). Time to first skin cancer was shortest in high‐risk (937 days) and very high‐risk (1390 days) groups, but this trend was not statistically significant (p = 0.094).

When BCCs were excluded, patients with higher SUNTRAC scores were again more likely to have positive histology (p = 0.024), with statistically significant differences observed between the low versus medium (p = 0.041) and low‐risk versus very high‐risk (p = 0.013) groups. Although median time to first diagnosis appears shorter in higher SUNTRAC grades, this trend was not statistically significant by non‐parametric testing (p = 0.60).

2.3. Discussion

With rising rates of renal transplantation in New Zealand and its close association with skin cancer, a robust screening service is vital. Almost one‐quarter of patients in our cohort developed skin cancer post‐transplant. Our study showed that skin cancer incidence increased as SUNTRAC grade increased, suggesting that SUNTRAC effectively stratifies risk of developing skin cancer when applied to our population. The study implied a trend between higher SUNTRAC grade and time to first skin cancer, although a larger study may be required to reach statistical significance. Patients deemed high‐risk experienced delays to initial skin checks, suggesting room for improvement in service provision by integrating this tool into the referral system.

Persistent barriers to accessing health care services in Māori and Pacific were evident, reinforcing known disparities, including in renal transplant and dermatology care. Loss to follow‐up in these groups highlights the ongoing need to address inequities, racism, communication barriers and broader social determinants. This requires targeted strategies and prioritisation of Māori and Pacific health frameworks to foster trust with these communities and improve continuity of care.

Limitations of this study include its retrospective design, incomplete documentation and high numbers of loss to follow‐up. Pre‐transplant skin cancer history relied on available documentation, which may be inaccurate. Skin cancer diagnosis dates were based on the first positive histology, though the precise onset was unknown. The absence of published data comparing nurse‐led VLCs and dermatologist‐led skin assessments introduces potential heterogeneity in clinical review. Patients with prior dermatological conditions may have received earlier reviews, and patients transferred across regions may have experienced delays. The small sample size and single‐centre nature limit the generalisability.

3. Conclusion

The SUNTRAC tool is valuable for initial dermatology triage in renal transplant patients to estimate their risk of developing skin cancer. The association of higher SUNTRAC grades with more skin cancers suggests that SUNTRAC could improve the prioritisation of initial dermatological review and follow‐up. While challenges such as loss to follow‐up in specific ethnic groups remain, the findings advocate for the integration of SUNTRAC into routine post‐transplant referral systems in New Zealand. In response, the referral template for renal transplant referrals to dermatology at Waikato has been updated to include SUNTRAC grade.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.