Body Mass Index and Nutritional Status With Immunotherapy Response in Head and Neck Cancer

Overview

Head and neck squamous cell carcinoma is a serious form of cancer that often affects the mouth, throat, larynx, and nearby structures. Many patients with advanced disease receive immunotherapy, a treatment that helps the immune system recognize and attack cancer cells. However, not every patient responds in the same way. This study examined whether nutritional status before treatment, including body mass index (BMI), recent weight loss, and the prognostic nutritional index (PNI), was linked to how long patients remained free of cancer progression after starting immunotherapy.

The main message is straightforward: static body size alone did not predict outcomes, but signs of worsening nutrition and immune reserve before treatment did. Patients who had lost weight before immunotherapy and those with a low PNI tended to have shorter progression-free survival.

Why nutrition may matter in cancer immunotherapy

Cancer and poor nutrition often go hand in hand. Patients with advanced head and neck cancer may have trouble swallowing, pain with eating, reduced appetite, taste changes, mouth sores, or difficulty chewing. These problems can lead to weight loss, muscle wasting, and lower protein levels in the blood. Malnutrition can weaken the body overall and may also affect immune function.

Immunotherapy relies on the body’s immune system. If a patient is already nutritionally depleted, their immune response may be less effective. That is why researchers are increasingly interested in whether simple measures of nutrition can help predict treatment outcomes and guide supportive care before therapy begins.

What the researchers studied

This was a cohort study using deidentified electronic health records from the Flatiron Health database, covering care from January 2014 through January 2024. The database included patients treated in both community and academic cancer centers across the United States, making the findings more broadly representative than a single-hospital study.

The study included adults with advanced head and neck squamous cell carcinoma who received immunotherapy, including nivolumab, pembrolizumab, cemiplimab, durvalumab, atezolizumab, avelumab, or ipilimumab. Patients were excluded if they were younger than 18 years, did not have squamous cell carcinoma, had missing stage or treatment information, or lacked the data needed to calculate BMI or PNI before treatment.

The main outcome was progression-free survival, which is the length of time after starting treatment during which the cancer does not get worse.

How nutritional status was measured

The study looked at three measures:

1. Baseline BMI: This is a standard weight-for-height measure. It was used to classify patients into BMI categories.
2. Pretreatment BMI change: Researchers examined whether patients had lost at least 2% of their BMI before starting immunotherapy, compared with those whose BMI stayed stable.
3. Prognostic nutritional index (PNI): This combines blood test results that reflect nutritional and immune status. In this study, a PNI below 45 was considered low, while 45 or higher was considered normal.

Unlike a single BMI measurement, BMI change and PNI may capture a patient’s current physiologic condition more accurately.

Who was included in the analysis

A total of 1,108 patients were analyzed. The average age was 66.2 years, and most patients were men, which reflects the usual sex distribution seen in head and neck squamous cell carcinoma. Among these patients, 79% had lost at least 2% of their BMI before treatment.

For the subgroup with laboratory data available, 471 patients were assessed for PNI. Of these, 67.9% had a low PNI.

Main findings

The study found that pretreatment weight loss mattered. Patients who had lost at least 2% of their BMI before immunotherapy had worse progression-free survival than patients whose BMI remained stable. The hazard ratio was 1.17, meaning the risk of cancer progression was modestly higher in the weight-loss group.

Median progression-free survival was 271 days in patients with pretreatment BMI loss, compared with 415 days in those with stable BMI.

PNI showed an even stronger association. Patients with low PNI had significantly shorter progression-free survival than those with normal PNI. The adjusted hazard ratio was 1.58, indicating a substantially higher risk of progression. Median progression-free survival was 213 days in the low-PNI group versus 566 days in the normal-PNI group.

Baseline BMI category itself was not independently associated with progression-free survival. In other words, simply being underweight, normal weight, overweight, or obese at the start of treatment was less informative than whether the patient had recently lost weight or had signs of poor nutritional reserve.

What these results mean

These findings suggest that dynamic nutritional measures are more useful than one-time body size measurements when estimating prognosis for patients with advanced head and neck cancer receiving immunotherapy.

A person may have a “normal” BMI and still be malnourished, especially if they have recently lost weight or if their blood markers suggest poor nutritional and immune status. This is particularly relevant in head and neck cancer, where swallowing problems and poor oral intake are common.

The results also support the idea that nutrition is not just a supportive issue; it may be part of cancer care that directly influences treatment effectiveness. If malnutrition worsens immune function, then improving nutrition before and during immunotherapy could potentially help outcomes, although this study did not test whether intervention changes survival.

Clinical implications

In practice, these results may encourage oncologists, otolaryngologists, dietitians, speech-language pathologists, and supportive care teams to assess nutrition early and often. Useful steps may include:

– Screening for recent weight loss before treatment begins
– Checking laboratory markers that contribute to PNI when available
– Referring patients for dietary counseling
– Addressing swallowing difficulties, pain, or mucositis that limit oral intake
– Considering high-calorie and high-protein supplements when appropriate
– Monitoring weight and intake throughout therapy

For some patients, early nutritional intervention may help preserve strength, improve tolerance of treatment, and possibly support immune response.

Strengths of the study

This research had several strengths. It included a large sample of patients from across the United States, reflecting real-world practice rather than a tightly controlled trial population. It also focused on practical measures that are relatively easy to obtain in routine care.

Another strength is the emphasis on pretreatment change rather than only baseline BMI. That approach recognizes that recent weight loss often signals active illness and declining reserves, which can be more meaningful than current weight alone.

Limitations to keep in mind

As with all observational studies, this research cannot prove that weight loss or low PNI causes poorer immunotherapy response. It shows an association, which may partly reflect more aggressive disease, worse general health, or other factors not fully captured in electronic records.

Other limitations include:

– Laboratory data for PNI were only available in a subset of patients
– The exact reasons for weight loss were not always known
– Nutritional interventions before treatment were not standardized or fully measured
– The study outcome was progression-free survival, not overall survival

Because of these limitations, the findings should be viewed as an important signal rather than definitive proof that improving nutrition alone will change cancer outcomes.

Take-home message

In this large U.S. cohort of patients with advanced head and neck squamous cell carcinoma treated with immunotherapy, pretreatment BMI loss and low PNI were linked to shorter progression-free survival, while baseline BMI was not. The study suggests that changes in weight and immune-nutritional status may offer more useful prognostic information than body size alone.

For patients and clinicians, the practical lesson is clear: assessing and supporting nutrition before immunotherapy may be an important part of optimizing cancer care.