Skin cancer at ASCO 2026: Five late-breaking studies

The ADAM trial (NCT03271372) is a phase 3, multicenter, double-blind, placebo-controlled study evaluating the adjuvant anti-PD-L1 immune checkpoint inhibitor, avelumab, in patients with stage 3 Merkel cell carcinoma (MCC) and lymph node (LN) metastases who had undergone definitive surgery and/or radiation therapy (RT), and had no radiologic evidence of residual disease.

One hundred patients, 52 with stage 3B disease and 48 with stage 3A disease, were randomized 1:1 to receive intravenous avelumab or placebo for up to 2 years on a de-escalating schedule. Median follow-up among relapse-free survivors was 4.2 years, median age was 70 years, and 93% of patients had received adjuvant RT.

Estimated MCC relapse rates were lower with avelumab than placebo at each reported time point: 12.8% versus 40.4% at 1 year, 21.3% versus 42.3% at 2 years, and 28.3% versus 44.5% at 3, 4, and 5 years. Grade 3/4 treatment-related adverse events (TRAEs) were reported in 15% of patients receiving avelumab (n=7) and in no patients receiving placebo.

In the endpoint analysis, relapse-free survival (RFS) numerically favored avelumab over placebo, with a stratified hazard ratio (HR) for failure of 0.61 (95% CI 0.32–1.16; p=0.132) and an adjusted stratified HR of 0.54 (95% CI 0.28–1.05; p=0.069). RFS events occurred in 16 versus 24 patients, respectively. For MCC relapse, the stratified HR was 0.51 (95% CI 0.26–1.00), and the adjusted stratified HR was 0.47 (95% CI 0.23–0.94), with 13 versus 23 events in the avelumab and placebo arms. For distant metastasis-free survival (DMFS), the stratified HR was 0.93 (95% CI 0.44–1.97), with 13 versus 15 events. The HRs for disease-specific survival (DSS) and overall survival (OS) were 1.81 (95% CI 0.43–7.55; 5 versus 3 events) and 2.37 (95% CI 0.73–7.73; 9 versus 5 events), respectively.

Key clinical takeaway

Adjuvant avelumab was associated with a reduced risk of MCC relapse in patients with LN metastases. The study investigators also suggest that the high MCC-specific survival observed in both the avelumab and placebo arms of the study point to the effectiveness of PD-(L)-1 blockade in the adjuvant and metastatic disease.

“We believe that these data will inform individualized decision making regarding adjuvant therapy in clinical practice,” said Dr Shailender Bhatia, speaking during the congress presentation.

→ Abstract: Bhatia S, Gooley T, Brohl AS, et al. ADAM trial: A multicenter, randomized, double-blinded, placebo-controlled, phase 3 trial of adjuvant avelumab (anti-PD-L1 antibody) in patients with Merkel cell carcinoma and lymph node metastases. Presented at: ASCO, Chicago, IL, USA. May 29 to June 2, 2026 Abstract. LBA9504.

Merkel cell carcinoma 

Adjuvant pembrolizumab associated with with a trend toward improved RFS in Merkel cell carcinoma

Presenter: Janice M. Mehnert, MD, New York University School of Medicine, NY, USA

What do the data show?

EA6174, known as STAMP (NCT03712605), is a randomized phase 3 trial evaluating adjuvant pembrolizumab in patients with resected MCC, and is the largest MCC trial to date. In the study, patients were randomized to pembrolizumab intravenously every 3 weeks for 17 doses (n=147) or standard of care (n=146), with a median follow-up of 47 months.

The analysis presented focused on MCC-specific outcomes and the effect of RT. MCC-specific outcomes were assessed using two RFS definitions: RFS_a, defined as relapse due to recurrence or death from any cause, and RFS_b, defined as MCC-specific recurrence or death.

RFS_a, was numerically improved with pembrolizumab compared with standard of care, but the difference between arms was not statistically significant (p=0.10). DMFS was improved among patients treated with pembrolizumab (p=0.05). However, a significant improvement was reported for RFS_b, with pembrolizumab compared with standard of care. The HR was 0.66 (90% CI 0.45–0.96), and 1-year RFS_b rates were 84% (90% CI 78–88) with pembrolizumab versus 73% (90% CI 67–79) with standard of care. At 2 years, RFS_b rates were 77% (90% CI 70–82) and 67% (90% CI 60–74), respectively (p=0.032).

The effect of pembrolizumab on RFS_b was maintained among patients who received any RT (n=131 pembrolizumab; n=123 standard of care; p=0.039). Among patients treated with RT concurrently, pembrolizumab did not affect outcomes. However, in patients who received RT sequentially before randomization (n=68 pembrolizumab; n=65 standard of care), pembrolizumab improved RFS_a (p=0.014), RFS_b (p=0.009), and DMFS (p=0.004).

Safety data showed a higher rate of grade ≥3 TRAEs in the pembrolizumab arm than in the standard-of-care arm, at 31% versus 4%.

Key clinical takeaway

Pembrolizumab given after surgery was associated with a trend toward improved RFS and significantly prolonged DMFS. Patients treated with pembrolizumab also experienced fewer MCC-related events than those receiving standard of care.

“Pembrolizumab improved DMFS, with no differences in OS seen at this time,” said Dr Janice M. Mehnert, speaking during the congress presentation. “The findings support that pembrolizumab may be of benefit after radiation therapy versus concurrently based on the radiation subset analysis, and we conclude that adjuvant pembrolizumab should not be routinely recommended, although therapy may be considered in patients at high risk for distant spread.”

→ Abstract:  Mehnert JM, Lee SJ, Gastman B, et al. Updated outcomes from STAMP: Surgically treated adjuvant Merkel cell carcinoma with pembrolizumab, a phase 3 trial: ECOG-ACRIN EA6174. Presented at: ASCO, Chicago, IL, USA. May 29 to June 2, 2026 Abstract. LBA9505

Melanoma 

Modified tumor-infiltrating lymphocyte therapy improves progression-free survival in anti-PD-1-resistant melanoma

Presenter: Lu Si, Peking University Cancer Hospital & Institute, Beijing, China

What do the data show?

MIZAR-003 (NCT06703398) is a multicenter, randomized, open-label, phase 2 trial evaluating GC101, a modified autologous tumor-infiltrating lymphocyte (TIL) therapy, in patients with advanced melanoma resistant to PD-1 antibodies. Patients were randomized 1:1 to GC101 TIL therapy or investigator-choice chemotherapy. The modified GC101 treatment regimen included no tumor resection, low-intensity preconditioning, infusion of interleukin-2-free TIL, and low dose anti-PD-1 support with sintilimab.

In an exploratory interim analysis, 84 patients had been randomized: 44 to GC101 TIL and 40 to investigator-choice chemotherapy. At a median follow-up of 5.2 months, GC101 TIL significantly improved median PFS compared with chemotherapy, at 4.1 months versus 1.6 months (HR 0.53; 95% CI 0.30–0.94; p=0.0310). ORR was 45.2% versus 5.4% (p=0.0018), and disease control rate was 80.6% versus 43.2% (p=0.0017), respectively.

Among patients with mucosal melanoma, median PFS was not reached with GC101 TIL versus 1.3 months with chemotherapy, and disease control rate was 100.0% versus 33.3%. Grade ≥3 TRAEs occurred in 36.8% and 27.5% of patients, respectively, while treatment-related serious adverse events occurred in 13.2% and 7.5%.

Key clinical takeaway

This interim analysis indicates that the modified GC101 TIL approach improved PFS and ORR compared with investigator-choice chemotherapy in patients with anti-PD-1-refractory advanced melanoma. Presenting the findings, study investigator Dr Lu Si described GC101 TIL as “an effective, less toxic, and more accessible treatment option for anti-PD-1-refractory advanced melanoma.”

→ Abstract: Si L, Chen Y, Zhang W, et al. A multicenter, randomized, controlled, open-label, phase 2 trial of autologous tumor-infiltrating lymphocytes (GC101 TIL) in patients with advanced melanoma. Presented at: ASCO, Chicago, IL, USA. May 29 to June 2, 2026. Abstract. LBA9509.

Merkel cell carcinoma 

ATR inhibitor, tuvusertib, plus avelumab shows antitumor activity in advanced anti-PD(L)-1 refractory Merkel cell carcinoma

Presenter: Evan Thomas Hall, Fred Hutch Cancer Center, Seattle, WA, USA

What do the data show?

MATRiX (NCT05947500) is a multicenter, randomized, open-label phase 2 trial evaluating tuvusertib, an ataxia telangiectasia and Rad3-related inhibitor (ATRi), alone or in combination with avelumab in patients with advanced anti-PD-(L)1-refractory MCC.

Patients were randomized 1:1 to tuvusertib monotherapy or tuvusertib plus avelumab. Arm 1 (n=10) received tuvusertib 180 mg orally on days 1–14 of each 21-day cycle, while Arm 2 (n=25) received the same tuvusertib schedule plus avelumab 1600 mg intravenously every 21 days. Patients progressing on monotherapy could cross over to the combination arm. Overall, 53% had primary ICI-refractory disease, and 65% had received at least 2 prior systemic therapies.

Tuvusertib monotherapy met prespecified futility criteria, with no responses observed among 10 patients. No objective responses were reported among the 4 patients who crossed over from Arm 1 to Arm 2 after disease progression.

Among 24 eligible patients treated with tuvusertib plus avelumab, 1 complete response and 4 partial responses were observed, corresponding to an ORR of 20.8% (95% CI 7.1–42.2). Responses occurred in 4 patients with primary ICI-resistant disease and 1 patient with acquired ICI-resistant disease. At data cutoff, 4 of the 5 responders remained progression-free, 182–273 days after starting treatment, while 1 patient relapsed at 479 days.

At 1 year, estimated PFS was 0% with tuvusertib monotherapy and 26.4% with tuvusertib plus avelumab (95% CI 10.8–45.1). Estimated 1-year OS was 29.2% with monotherapy and 36.5% with the combination. Grade ≥3 TRAEs occurred in 80% of patients in Arm 1 and 58% in Arm 2.

Key clinical takeaway

The combination of the ATRi tuvusertib plus avelumab demonstrated durable antitumor activity in this anti-PD-(L)1 treatment-refractory population, including responses in patients with both primary and acquired ICI-resistant disease. In contrast, tuvusertib monotherapy showed no signal of anticancer activity.

Presenting the findings during the congress, study investigator Dr Evan Hall added: “The results suggest that ATR inhibition may sensitize MCC to PD-(L)1 blockade in a post-ICI setting, and a future study investigating lower-dose radiation in combination with ATR inhibition and ongoing checkpoint blockade is planned.”

→ Abstract: Bhakuni R, Hall ET, Gooley T, et al.MATRiX: A randomized phase 2 trial of tuvusertib (ATR inhibitor) with or without avelumab in advanced anti-PD(L)-1 refractory Merkel cell carcinoma. Presented at: ASCO, Chicago, IL, USA. May 29 to June 2, 2026 Abstract. LBA9514.

Melanoma 

Neoadjuvant daromun confirms recurrence-free survival benefit in locally advanced melanoma

Presenter: Katharina C. Kaehler, MD, University Hospital (UKSH), Campus Kiel, Department of Dermatology, Germany

What do the data show?

PIVOTAL (NCT02938299) is an open-label, randomized, multicenter, phase 3 trial evaluating neoadjuvant daromun in patients with resectable, locally advanced stage 3 melanoma. This updated analysis reports longer-term RFS and EFS data after previous trial findings showed that daromun met its primary endpoint versus upfront surgery

Patients with skin and/or lymph node metastatic melanoma suitable for complete surgical resection were randomized 1:1 to receive 4 weekly IT injections of daromun followed by surgery, or upfront surgery alone. Prior surgery, RT, and/or systemic therapy were permitted, as was approved adjuvant treatment after surgery.

At more than 36 months’ median follow-up, the updated analysis confirmed improved RFS with daromun compared with upfront surgery (HR 0.60; p=0.003). The overall EFS sensitivity analysis was consistent with the RFS findings (HR 0.66; 95% CI 0.47–0.92). EFS results were also consistent in patients with recurrent disease (HR 0.59; 95% CI 0.41–0.85), including those who had previously received only surgery and/or RT (HR 0.55; 95% CI 0.34–0.89) and those who had received prior systemic therapy (HR 0.63; 95% CI 0.36–1.08). Treatment-related adverse events at longer follow-up were consistent with previous reports, and no new safety risks were identified.

Key clinical takeaway

Longer follow-up confirmed a reduction in the risk of recurrence or death with neoadjuvant IT daromun compared with upfront surgery in patients with resectable, locally advanced stage 3 melanoma. The EFS sensitivity analyses were consistent with the primary RFS findings across the overall trial population, including patients with recurrent disease, with or without prior systemic therapy.

After presenting the key findings at the meeting, presenter and study investigator Dr Katharina C. Kähler concluded: “Intralesional daromun represents an effective, safe alternative for patients who failed or were not eligible for neoadjuvant ICIs.”

→ Abstract: Kaehler KC, Ziemer M, Hassle JC, et al. Neoadjuvant intralesional daromun (L19IL2/L19TNF) in resectable locally advanced melanoma: An update on the primary outcome and sensitivity analyses (EFS) from the PIVOTAL phase 3 trial. Presented at: ASCO, Chicago, IL, USA. May 29 to June 2, 2026. Abstract. LBA9517.

This content has been developed independently by Touch Medical Media for touchDERMATOLOGY. Views expressed are the speaker’s own and do not necessarily reflect the views of Touch Medical Media. This article was created by the editorial team utilizing AI as an editorial tool (ChatGPT 5.5 [Large language model]. https://chat.openai.com/chat.) The content was developed and edited by human editors. No funding was received in the publication of this article.

Cite: ASCO 2026 Plenary late-breaking abstracts: Key takeaways. touchDERMATOLOGY. 4 June 2026.

Editor: Gina Furnival.