Welcome back to this month's journal review. We're covering the July 2026 issue of the Journal of the American Academy of Dermatology, and I've picked four pieces that I think are genuinely relevant to how you counsel patients and think about resource allocation in oncologic dermatology — a pharmacoepidemiology brief report on antibiotics and immunotherapy outcomes, a population-level survival analysis of three rare cutaneous sarcomas, a Medicare cost analysis pitting superficial radiation against Mohs surgery, and a survey study on indoor tanning and age at melanoma diagnosis. Let's get into it.

First up is a brief report — a retrospective cohort study using the TriNetX federated electronic health record network — looking at whether antibiotic exposure before starting immune checkpoint inhibitor therapy affects survival in Merkel cell carcinoma, with melanoma and cutaneous squamous cell carcinoma run in parallel as validation cohorts. The background here is something you already intuit: checkpoint inhibitors are now foundational across cutaneous squamous cell carcinoma, melanoma, and Merkel cell carcinoma, but response is heterogeneous, and there's accumulating evidence that gut microbial disruption from systemic antibiotics blunts checkpoint inhibitor efficacy in melanoma and squamous cell carcinoma. Nobody had looked at this in Merkel cell carcinoma, largely because it's rare — but the authors point out a nice clinical hook: Merkel cell carcinoma classically presents as a rapidly growing red nodule that gets misdiagnosed as cellulitis or an abscess, which sets these patients up for unnecessary antibiotic courses right before they'd otherwise start immunotherapy.

Methodologically, they used TriNetX specifically because Merkel cell carcinoma's rarity makes single-institution study underpowered — a federated multi-institutional claims and EHR database gives you the numbers. They used propensity, or balancing, score matching to equalize antibiotic-exposed and unexposed groups on age, comorbidities, cardiovascular disease, and baseline labs like neutropenia and lymphopenia, which is standard practice in this kind of retrospective database work to reduce confounding by indication — though as we'll get to, it doesn't eliminate it. Running melanoma and squamous cell carcinoma alongside Merkel cell carcinoma wasn't just incidental; it let them validate that their pipeline reproduces the previously published antibiotic-survival signal in those two cancers before trusting the novel Merkel cell carcinoma finding.

The results: in Merkel cell carcinoma, 109 antibiotic-exposed patients were matched to 109 controls, and survival was significantly worse in the antibiotic group within the first four months after starting checkpoint inhibitor therapy — roughly a two-fold increase in mortality risk, statistically significant — but that difference washed out by eight and twelve months. In melanoma, with over three thousand patients per arm, there was a modest but significant survival decrement at one month post-initiation that also stabilized by a year. Cutaneous squamous cell carcinoma was the outlier — with about 1,150 patients per arm, the survival reduction wasn't just early, it persisted all the way through twelve months, and that effect size was the largest of the three.

The authors' interpretation is that this supports a shared biological mechanism — antibiotic-induced gut dysbiosis impairing anti-tumor immunity — and that the timing pattern actually makes biological sense: the harm clusters in the window right after checkpoint inhibitor initiation, which lines up with what we know about the microbiome typically recovering somewhere between one and three months after antibiotic exposure. Squamous cell carcinoma's more sustained signal is flagged as possibly reflecting slower immune reconstitution, though that's somewhat speculative on their part. Now, the honest limitations: this is retrospective claims data, so there's no way to separate cancer-specific mortality from all-cause mortality, and confounding by indication is a real concern here — patients who needed antibiotics may have been sicker, more infected, or more immunocompromised at baseline in ways matching didn't fully capture. Some of their sensitivity analyses weren't statistically significant either.

So what do you do with this clinically? I'd call this hypothesis-generating rather than practice-changing in isolation, but it converges with a growing melanoma and squamous cell carcinoma literature to form a genuinely actionable pattern: before you or a medical oncology colleague starts checkpoint inhibitor therapy, it's worth pausing on empiric antibiotics for a lesion that looks like it might be infected but could be tumor — which is exactly the diagnostic trap Merkel cell carcinoma sets. It doesn't mean withholding antibiotics when truly indicated, but it supports being more deliberate about antibiotic stewardship in the weeks surrounding immunotherapy initiation.

Second article — a population-based brief report using the Surveillance, Epidemiology, and End Results database, or SEER, examining relative survival in three rare cutaneous soft tissue malignancies: dermatofibrosarcoma protuberans, Kaposi sarcoma, and pleomorphic sarcoma, the last category lumping together undifferentiated pleomorphic sarcoma, pleomorphic dermal sarcoma, atypical fibroxanthoma, and malignant fibrous histiocytoma. The gap they're addressing is that nobody had really examined these three cancers using relative survival rates — which, as they explain, compare observed survival in the cancer cohort to expected survival in a demographically matched cancer-free population, which is a nice way of stripping out competing mortality causes that would otherwise muddy a straightforward overall survival analysis, especially in an older, comorbid population.

They pulled just over seven thousand dermatofibrosarcoma protuberans cases, about eighty-six hundred Kaposi sarcoma cases, and fifty-seven hundred pleomorphic sarcoma cases diagnosed between 2000 and 2021, then calculated age-standardized five-year relative survival across intersections of age group, race and ethnicity, and sex — deliberately looking at intersectional subgroups rather than just top-line numbers, which is really the point of the paper.

Top line: pleomorphic sarcoma and Kaposi sarcoma both showed five-year relative survival significantly below the expected one-hundred-percent baseline — roughly 71% for pleomorphic sarcoma and 77% for Kaposi sarcoma — both clinically meaningful reductions. Dermatofibrosarcoma protuberans, reassuringly, did not differ significantly from expected survival overall, and even in the subgroups that did show statistically significant reductions — older men, patients of color — the absolute relative survival rates stayed above 97%, which the authors are careful to frame as statistically real but clinically close to negligible. The one exception worth remembering: men aged 75 and older with dermatofibrosarcoma protuberans had a more notable reduction, down around 88%.

Kaposi sarcoma is where the disparities get clinically substantial. The worst relative survival was in the youngest patients, ages 15 to 44, at about 65%, actually better in patients 75 and up, around 92%. Women fared worse than men overall — 67% versus 77% — and that gap was dramatic in younger patients specifically, with young women at 47% relative survival versus 66% in young men. By race, Native American and Asian patients had the lowest Kaposi sarcoma survival, in the mid-60s percent range, while white and Hispanic patients were around 78%. And cutting by both race and sex together, Asian, Black, and Hispanic women all had substantially lower relative survival than their male counterparts — differences on the order of 7 to 20 percentage points.

Pleomorphic sarcoma showed similar overall survival between men and women, but age-and-sex-stratified data revealed that younger women actually did better than younger men, while older women fared worse than older men — survival for women dropped from about 82% at the youngest ages down to 65% in patients 75 and older. And the single worst subgroup in the entire study was Black men with pleomorphic sarcoma, at a relative survival of roughly 48%.

The authors are appropriately cautious in their limitations: Kaposi sarcoma and pleomorphic sarcoma subtype granularity is poor in SEER, which blurs prognostically distinct entities together; Kaposi sarcoma relative survival can't cleanly separate tumor-attributable deaths from other HIV-related mortality; several race-sex subgroups couldn't even be age-standardized due to small numbers; and the subgroup findings are explicitly descriptive, not causally tested. So what's the takeaway for you? Dermatofibrosarcoma protuberans prognosis is reassuring across the board and this gives you solid population-level data for patient conversations. But the Kaposi sarcoma and pleomorphic sarcoma disparities — especially young women and racial minorities with Kaposi sarcoma, and Black men with pleomorphic sarcoma — are large enough to raise real questions about diagnostic delay and unequal access to care, which the authors explicitly flag as needing further study. This isn't a surgical technique paper, but it's useful epidemiologic context, particularly if you're the one making referral and follow-up decisions in these populations.

Third article, and this one has real operational teeth: a cost analysis using the Centers for Medicare and Medicaid Services, or CMS, provider and service public-use data set, comparing costs of superficial radiation therapy — with and without image guidance — against Mohs micrographic surgery for nonmelanoma skin cancer. The setup is straightforward: superficial radiation therapy use is rising, image-guided superficial radiation therapy in particular is being marketed on claims of better precision and even cost-effectiveness, but nobody had recently audited what it actually costs relative to Mohs.

Methodologically, they queried Medicare's public billing data from 2018 through 2022 for the superficial radiation delivery code, the simulation codes — simple, intermediate, and complex, corresponding to one, two, or three-plus treatment areas — and the ultrasonic guidance add-on code. Using CMS claims data here makes sense because it's the actual national fee schedule and actual billing behavior, not a modeled or theoretical cost — this is what's really being reimbursed, at scale, across the country.

The trend data alone is notable: the number of dermatologists billing superficial radiation grew by about a third from 2018 to 2022, but the number using image guidance exploded roughly twelve-fold over the same period — a wildly disproportionate uptake. Even more strikingly, the use of simple radiation simulation billed per session nearly doubled in frequency, going from about half of sessions in 2018 to 90% of sessions in 2022, and climbing to 95% once you include the intermediate and complex simulation codes — meaning simulations are now being billed almost every single treatment day, which is exactly the utilization pattern regulators have started pushing back on.

On cost: in 2022, a full course of image-guided superficial radiation — 12, 20, or 25 fractions — cost anywhere from about two-to-one up to nearly six-to-one compared to a typical two-stage Mohs case with complex linear closure, and even against Mohs cases requiring flap reconstruction, image-guided radiation still ran one-and-a-half to over four-fold more expensive. In real dollar terms, a 20-fraction image-guided course runs around eighty-four hundred dollars, a 25-fraction course over ten thousand, compared to roughly sixteen hundred dollars for Mohs with complex closure or under nineteen hundred with flap reconstruction. And since hypofractionated superficial radiation isn't how it's typically delivered in practice, the authors argue the 15-to-20 fraction range is the realistic comparison — meaning routine real-world image-guided courses are costing multiple times what equivalent Mohs surgery costs.

This connects to real regulatory movement the authors highlight: a new 2026 local coverage determination will cut reimbursement by disallowing daily repeat simulations and declaring high-frequency ultrasound guidance not medically necessary, and it will also deem electronic brachytherapy not medically reasonable for this indication — and the American College of Mohs Surgery, together with the American Society for Radiation Oncology, has jointly endorsed restricting the daily billing of ultrasound guidance and simulation codes. The authors also raise a technical point worth knowing: the high-frequency ultrasound used for treatment planning can't reliably resolve tumor depth under a millimeter at typical frequencies below 30 megahertz, undercutting some of the precision claims.

Limitations are narrow but real — this only captures the specific CPT-coded costs, not facility fees, and doesn't account for patient experience or preference, and the authors acknowledge superficial radiation still has a legitimate role for genuinely poor surgical candidates due to comorbidity, advanced age, or surgical refusal. But the bottom line is unambiguous and, I'd argue, practice-relevant: superficial radiation, and especially image-guided superficial radiation, is substantially more expensive than Mohs surgery, the gap is widening as image-guidance and simulation billing patterns increase, and this data set gives you a very concrete, citable number for conversations with patients, payers, and referring colleagues who may be hearing cost-effectiveness marketing claims that this data directly contradicts.

Last article — a survey-based cohort study from the Tom Baker Cancer Centre in Calgary, examining indoor tanning exposure and age at melanoma diagnosis. This builds on the same group's earlier work showing indoor tanning correlated with melanoma diagnosis more than a decade earlier than in non-users; here they drill into dose-response — timing of first use, session intensity, duration — and clinicopathologic correlates.

Methodologically, they administered a 24-item sun-behavior and tanning survey at consultation to patients with cutaneous melanoma — excluding ocular, mucosal, and acral lentiginous subtypes since those have distinct, largely UV-independent biology — and linked survey responses to the Alberta Cancer Registry for clinicopathologic and molecular data. Completion was essentially universal, which the authors note as a strength. They predefined early users as those starting indoor tanning before age 25% and heavy users as those in the top quartile of cumulative sessions, then adjusted their models for skin type, family history, and sun exposure to isolate the tanning bed effect specifically. A survey approach here is really the only option, since tanning bed exposure isn't something you'll find coded anywhere in a medical record — you have to ask the patient directly.

Among 854 patients, median age 62, and overwhelmingly fair-skinned, about a third reported ever using indoor tanning, and women were more likely to report use, started earlier, and tanned more frequently than men. The core finding: patients who'd ever used indoor tanning were diagnosed with melanoma at a median age of 52, versus 63 in never-users — an eleven-year gap that held up consistently across sex, skin type, and family history, and after full adjustment, indoor tanning use was independently associated with diagnosis nearly ten years earlier, which is both statistically significant and clearly clinically meaningful.

The dose-response signal is the most striking part: patients who started tanning before age 25 were diagnosed a full seventeen years earlier than those who started later — 41 versus 58 — while heavy lifetime users only trended toward earlier diagnosis without reaching significance, suggesting that timing of initiation matters more than cumulative dose in this cohort. Indoor tanning users were also more likely to develop melanoma on intermittently sun-exposed skin and were more likely to carry BRAF V600E mutations, though those differences, while statistically significant, were more modest in absolute terms.

The authors frame this temporal gradient — earlier and younger initiation tracking with earlier diagnosis — as supporting a causal relationship, consistent with prior meta-analyses linking early, frequent indoor tanning to elevated melanoma risk. Limitations are the expected ones for this design: retrospective, single tertiary-center referral population which may skew toward more aggressive disease, missing molecular data in some patients, and residual confounding by sun exposure despite statistical adjustment.

Clinically, this isn't a surgical or technique paper, but it's directly useful for how you risk-stratify and counsel. A young patient presenting with melanoma is worth a specific, direct tanning-bed history, not just a general sun-exposure question, since initiation before age 25 tracked with a nearly two-decade earlier diagnosis in this cohort, and indoor tanning history correlated with distinct clinical and molecular features including BRAF status. It also reinforces the public health argument for restricting youth access to tanning beds — useful ammunition if you're involved in advocacy or patient education efforts, even if it doesn't change what happens on your surgical table.

That wraps up this month's four articles. Taken together, there's a nice thread running through this issue — antibiotic timing around immunotherapy, demographic disparities in rare sarcoma survival, the real financial cost of radiation alternatives to Mohs, and the modifiable risk of indoor tanning — all reminders that outcomes in cutaneous oncology are shaped as much by systemic, epidemiologic, and economic factors as by what happens under the microscope. Thanks for listening, and I'll see you next month.