This Week in Oncology — May 21, 2026

Welcome to This Week in Oncology. This week we're covering 10 notable papers spanning new frontiers for antibody-drug conjugates, refinements in perioperative therapy, and major updates in tough-to-treat cancers. Let's dive in.

We begin this week with antibody-drug conjugates, focusing on a major clinical success in triple-negative breast cancer and new insights into the mechanisms of resistance.

In a report from the BEGONIA platform study, published in the Annals of Oncology, investigators evaluated the TROP2-directed antibody-drug conjugate datopotamab deruxtecan, or Dato-DXd, combined with the PD-L1 inhibitor durvalumab as a first-line treatment for unresectable or metastatic triple-negative breast cancer [1]. The study included two arms: one for all-comers regardless of PD-L1 status, and another specifically for patients with PD-L1-high tumors. The results were impressive and consistent across both groups. In the all-comer arm, the confirmed objective response rate was 79%, with a median duration of response of nearly 18 months and a median progression-free survival of 14 months. The PD-L1-high arm showed a similar objective response rate of about 82%, although survival data are still immature. The safety profile was manageable with no new signals. These findings position Dato-DXd plus durvalumab as a highly active and durable first-line option for metastatic TNBC.

While ADCs like Dato-DXd show great promise, resistance remains a key challenge. A preclinical study in Cancer Cell provides critical insights into how this happens [2]. Investigators studied tumors from patients with urothelial carcinoma who developed resistance to enfortumab vedotin, a NECTIN4-targeting ADC. They identified a fascinating resistance mechanism: the cancer cells still had high levels of the NECTIN4 target on their surface, but they became defective at taking up the ADC. A protein called AKR1C1 was found to be the culprit. It both prevents the NECTIN4-ADC complex from entering the cell and actively pumps the ADC back out via extracellular vesicles. This reduces the amount of cytotoxic payload delivered inside the cancer cell. Importantly, in preclinical models, pharmacologically inhibiting AKR1C1 restored the cell's ability to take up the ADC and re-sensitized resistant tumors to therapy. This work defines a clinically relevant resistance state and identifies a potential new strategy for overcoming ADC therapy failure.

Next, two studies from the Journal of Clinical Oncology explore opposite ends of the spectrum in perioperative care: de-escalation in early breast cancer and intensification in muscle-invasive bladder cancer.

First, we have the final 5-year survival analysis of the WSG TP-II trial [10]. This study randomized patients with hormone receptor-positive, HER2-positive early breast cancer to one of two neoadjuvant regimens: a chemotherapy-free arm with endocrine therapy plus trastuzumab and pertuzumab, or a chemotherapy arm with paclitaxel plus the same dual HER2 blockade. The primary endpoint, which was previously reported, showed a much higher rate of pathologic complete response, or pCR, with chemotherapy. However, this new survival analysis tells a different story. After five years of follow-up, overall survival was 100% in the endocrine therapy arm versus 97.9% in the chemotherapy arm. Event-free survival rates were also very similar and excellent in both groups. This is a crucial finding. It confirms that for this specific subtype of breast cancer, a de-escalated, chemotherapy-free neoadjuvant approach can yield outstanding long-term survival outcomes, allowing adjuvant therapy to be guided by pCR status. This supports sparing many patients from the toxicity of chemotherapy.

In contrast, a phase 3 trial in high-risk muscle-invasive bladder cancer argues for treatment intensification [4]. After patients underwent radical cystectomy and perioperative chemotherapy, they were randomized to either adjuvant pelvic radiotherapy or observation. The primary endpoint was 2-year locoregional recurrence-free survival. After a median follow-up of 47 months, adjuvant radiotherapy significantly improved this outcome, with a 2-year locoregional recurrence-free survival of 87% compared to 76% in the observation arm. While the secondary endpoints of disease-free, cancer-specific, and overall survival showed trends favoring radiotherapy, they did not reach statistical significance. Still, the trial suggests that for patients with high-risk features after cystectomy, adding adjuvant pelvic IMRT improves locoregional control without significant additional toxicity and should be considered.

This week also brought significant survival updates for two cancers with historically poor prognoses: gastric cancer with peritoneal metastasis and metastatic uveal melanoma.

The DRAGON-01 trial, a phase 3 study published in JAMA Oncology, could change practice for gastric cancer with peritoneal-only metastasis [5]. This Chinese study randomized patients to receive either standard intravenous paclitaxel plus oral S-1, or an experimental regimen that added intraperitoneal paclitaxel to the intravenous paclitaxel and S-1 backbone. The rationale is to deliver higher drug concentrations directly to the site of disease. The results were clearly positive. Median overall survival was significantly longer in the intraperitoneal group, at 19.4 months compared to 13.9 months in the standard therapy group. That's a survival improvement of more than five months. Progression-free survival was also improved, and importantly, the addition of intraperitoneal therapy did not increase the rate of severe adverse events. This trial provides strong evidence for a new first-line standard of care in this patient population.

Meanwhile, in the Annals of Oncology, we have the final 5-year survival analysis of the pivotal phase 3 trial for tebentafusp in metastatic uveal melanoma [6]. Tebentafusp is already the standard of care for previously untreated, HLA-A*02:01-positive patients. This long-term follow-up confirms its durable benefit. The median overall survival was 21.6 months with tebentafusp versus 16.9 months for investigator's choice. More strikingly, at the 5-year mark, the overall survival rate was 16% with tebentafusp, double the 8% seen in the control arm. The benefit was maintained even in patients with poor prognostic features or those who experienced radiographic progression as their best response. The analysis also showed that deep reductions in circulating tumor DNA by week 9 were associated with longer survival, confirming its utility as an early biomarker of response.

Finally, we turn to the future, with new tools for monitoring disease, assessing risk, and a preclinical look at overcoming immunotherapy resistance.

From the Journal of Clinical Oncology, an analysis of the GMMG-HD7 trial establishes serum mass spectrometry as a powerful tool for monitoring multiple myeloma [3]. This minimally invasive blood test can reliably detect and quantify monoclonal proteins, serving as a method for assessing measurable residual activity. The study found that achieving negativity on the mass spectrometry test was strongly associated with superior progression-free survival, particularly at later time points during maintenance therapy. When combined with traditional bone marrow MRD assessment, it further refined risk stratification. These findings support using serum mass spectrometry for routine disease monitoring, complementing bone marrow testing and potentially guiding risk-adapted treatment. This type of evolving evidence is exactly what will be incorporated into the regularly updated ASCO Living Guideline for Multiple Myeloma, also published this week, which serves as a continuously updated resource for clinicians [7].

In breast cancer, a study in Science Translational Medicine introduces a powerful new AI-based risk model for primary prevention [8]. Developed using mammogram images, this tool provides a 10-year absolute risk of developing breast cancer. In validation across diverse populations from the United States and Sweden, the AI model significantly outperformed existing clinical risk tools, like the Tyrer-Cuzick model, as well as another image-based AI tool called Mirai. For instance, in one cohort, the new AI tool identified 33% of future breast cancers among the top 10% of high-risk individuals, compared to only 20-24% for other models. This demonstrates its potential to substantially improve risk stratification and personalize primary prevention strategies.

Lastly, a paper in Nature Cancer explores a novel strategy to overcome resistance to immune checkpoint inhibitors [9]. Researchers found that tumors can promote a type of 'emergency' myelopoiesis, generating immunosuppressive neutrophils that dampen the anti-tumor immune response. They identified that a receptor called CysLTR1, which is targeted by existing drugs for asthma, plays a key role in this process. In mouse models, both genetic and pharmacologic inhibition of CysLTR1 reprogrammed these neutrophils from a tumor-promoting to an anti-tumor state. This 'disarming' strategy enhanced anti-tumor immunity and, critically, overcame resistance to anti-PD1 therapy. These findings open the door for rapid clinical translation of CysLTR1 inhibitors to improve cancer immunotherapy outcomes.

If you only have time for one paper this week, make it the DRAGON-01 trial in JAMA Oncology [5]. This phase 3 study showed a clear overall survival benefit by adding intraperitoneal paclitaxel for gastric cancer with peritoneal metastasis, a notoriously difficult-to-treat condition. This is a simple, effective strategy that could change first-line practice.

Here are the key takeaways from this week in Oncology.

First: In first-line metastatic triple-negative breast cancer, the combination of datopotamab deruxtecan and durvalumab shows a very high and durable response rate, emerging as a powerful new option [1].

Second: For hormone receptor-positive, HER2-positive early breast cancer, a neoadjuvant chemo-free regimen of endocrine therapy plus dual HER2 blockade yields excellent long-term survival, comparable to a chemo-containing regimen, supporting de-escalation strategies [10].

Third: In gastric cancer with peritoneal-only metastasis, adding intraperitoneal paclitaxel to systemic therapy significantly improves overall survival by over five months, establishing a new potential standard of care [5].

Fourth: In high-risk muscle-invasive bladder cancer post-cystectomy, adjuvant pelvic radiotherapy significantly reduces the risk of locoregional recurrence and should be considered [4].

Fifth: For monitoring multiple myeloma, serum mass spectrometry is a highly sensitive, minimally invasive tool that complements bone marrow MRD for prognostication and may guide future treatment decisions [3].

That's your roundup for This Week in Oncology. The full transcript and references are available on the episode page in your AudioScholar library. This is an AI-curated summary — for clinical decisions, always consult primary sources and current guidelines. See you next week.

This is an automated summary generated by artificial intelligence, which can make mistakes. Always review the original source materials.