Introduction

Head and neck cancer treatment is moving in two directions worth understanding together: new antibody-based strategies for patients whose disease has already progressed through checkpoint inhibitor therapy and chemotherapy, and a clearer biological rationale for how immunotherapy and radiation should (and shouldn't) be sequenced together.

After Checkpoint Failure: A Bispecific Antibody Offers a New Option

For recurrent or metastatic head and neck squamous cell carcinoma that has progressed after PD-(L)1 inhibitor therapy and platinum-based chemotherapy, EGFR-targeted therapy (cetuximab) has long served as a fallback option, though response rates have historically been modest, around 20 percent. Part of the problem is biological: suppressing EGFR alone can upregulate other kinases, such as MET, allowing tumors to develop resistance relatively quickly.

A bispecific antibody targeting EGFR alongside a second target expressed on head and neck cancer stem cells was tested as monotherapy in this heavily pretreated, checkpoint- and chemotherapy-exposed population (100 percent of patients had received prior checkpoint therapy, and a large share had also received a PARP inhibitor-based regimen in trial). Results were genuinely notable for a single agent in this setting: investigator-assessed overall response rate around 47 percent, including a 15 percent complete response rate, with median progression-free survival of 6.8 months and overall survival over a year. Responses also came quickly, with a median time to response of about 6.6 weeks. A follow-up study is already testing this same antibody moved into the first-line setting in combination with chemotherapy.

(A note on sourcing: the specific bispecific antibody in this trial could not be independently confirmed against the primary abstract without slide access; petosemtamab, an EGFR/LGR5-targeted bispecific antibody with published monotherapy response rates in the 36-37 percent range in similar populations, is the closest published match but the figures above reflect the presenter's own numbers, which run somewhat higher, and should be verified against the original source before publication.)

Neoadjuvant Immunotherapy: A Small But Striking Signal in Locally Advanced Disease

Neoadjuvant immunotherapy before definitive treatment has become an increasingly preferred approach for locally advanced head and neck cancer, building on prior data (including the KEYNOTE-689 trial) showing improved outcomes, though overall survival data from that trial are still pending. A proof-of-concept study tested a different, novel bispecific antibody blocking both PD-1 and a second immune checkpoint target, combined with a short course of chemotherapy, as neoadjuvant treatment before surgery in a population skewed toward advanced, high-comorbidity disease (T4 and N2/N3 tumors).

The results were striking for a small proof-of-concept trial: an overall pathologic complete response rate of 53 percent, compared with roughly 3 percent historically reported with chemotherapy alone in this setting, along with a 100 percent R0 (margin-negative) resection rate and no apparent increase in surgical bleeding risk, a specific concern surgeons had going in given the antiangiogenic component of the regimen. Only one patient had a recurrence at just over 20 months of follow-up. Whether this translates into an overall survival benefit remains unknown, and the trial's small size and single-arm design are real limitations, but the depth of response is compelling enough to warrant a larger, comparative trial.

Other Notable Signals: Salivary Gland, Adenoid Cystic, and Nasopharyngeal Cancer

A few additional, smaller studies are worth knowing about, each addressing a specific and historically difficult-to-treat head and neck subtype:

Androgen receptor-positive salivary gland carcinoma, which has previously responded poorly to single-agent androgen-pathway blockade, showed a low objective response rate but a notably low progression rate and durable responses (out to two years) when androgen deprivation therapy was combined with an androgen receptor inhibitor, suggesting dual androgen-pathway blockade may be more effective than either approach alone.

Adenoid cystic carcinoma, a notoriously difficult-to-target tumor with a roughly 70 percent rate of eventual lung or liver metastasis after local therapy, showed encouraging, durable responses (continuing to be seen beyond a year) with a locoregional, catheter-delivered therapy in a 130-patient study, with response rates clearly better than historical expectations for this disease. A cooperative group study is now being planned to confirm this signal.

Nasopharyngeal carcinoma maintenance therapy was tested in a proof-of-concept study substituting an immunotherapy-based maintenance regimen for standard cisplatin-containing maintenance after chemoradiation, aiming for comparable efficacy with potentially less toxicity; early results showed a numerically favorable trend in progression-free and overall survival, though the study was designed only to establish a signal worth testing in a larger randomized trial, not to change practice on its own.

The Bigger Picture: Why Concurrent Immunotherapy and Radiation May Be the Wrong Combination

Across thoracic and head and neck cancer, trials combining immunotherapy concurrently with radiation have been consistently disappointing, in contrast to trials using immunotherapy before or after radiation (sequentially) rather than at the same time. The likely biological explanation: radiation given concurrently with immunotherapy activates T cells and draws them toward the tumor site, only to have those same T cells killed off by the radiation itself. Neoadjuvant immunotherapy, by contrast, primes the immune system first, and if the tumor is then surgically removed, there's no longer a local tumor site drawing T cells into a radiation field, since immunotherapy is instead addressing microscopic, systemic disease rather than one specific irradiated area. This general principle, priming immunity first, then treating locally, appears to be a more effective strategy than combining both simultaneously, a lesson that should inform how future head and neck (and lung) trials are designed.

Separately, a Japanese trial examined whether postoperative radiation truly needs to start within six weeks of surgery, a widely followed but not strictly evidence-based rule. That trial suggested radiation does not necessarily need to start by that specific six-week mark as long as chemotherapy is being given in the interim, a useful, practical finding for patients whose recovery or scheduling makes that six-week window difficult to hit, though it has not yet changed formal guidelines.

For Patients

For patients whose head and neck cancer has progressed after standard immunotherapy and chemotherapy, a new antibody-based option targeting two pathways at once is showing meaningfully better and faster responses than older fallback treatments, though it remains investigational. For patients with locally advanced head and neck cancer being considered for immunotherapy before surgery, early data suggest that combining two immune-targeting drugs together, rather than just one, may substantially increase the chance of the tumor being completely eliminated by the time of surgery, though this needs confirmation in larger trials before becoming standard. And a general principle worth understanding: immunotherapy and radiation given to the same area at the same time do not appear to work well together, whereas giving immunotherapy first and treating locally afterward (with radiation or surgery) appears to work better, a pattern now being applied across several cancer types.

Key Takeaways

  • A bispecific antibody targeting EGFR and a second pathway showed roughly 47 percent response rate (including 15 percent complete responses) as monotherapy in heavily pretreated head and neck cancer patients who had already failed checkpoint therapy and chemotherapy; the specific agent's identity needs independent confirmation.

  • A small proof-of-concept trial combining a PD-1/second-checkpoint bispecific antibody with chemotherapy before surgery achieved a 53 percent pathologic complete response rate and 100 percent margin-negative resection in locally advanced disease, though it requires larger confirmatory trials.

  • Combining immunotherapy concurrently with radiation has consistently underperformed compared with sequential approaches (immunotherapy before or after, rather than during, radiation), likely because concurrent radiation kills the very T cells that immunotherapy activates near the tumor.

  • A Japanese trial suggests postoperative radiation does not necessarily need to start within six weeks of surgery if chemotherapy bridges the interval, though this has not yet changed formal guidelines.

References

  1. Phase 2 trial of a bispecific antibody monotherapy in checkpoint- and chemotherapy-refractory recurrent/metastatic head and neck squamous cell carcinoma. Presented ASCO 2026.

  2. Proof-of-concept neoadjuvant trial of a PD-1-targeted bispecific antibody plus chemotherapy in locally advanced head and neck squamous cell carcinoma. Presented ASCO 2026.

  3. Keynote-689 Investigators. Perioperative pembrolizumab for locally advanced head and neck squamous cell carcinoma. Presented ASCO 2025.