Immunotherapy has become a routine component of cancer care, but its growing use has introduced complex questions about treatment duration, resistance, toxicity, retreatment, and patient preference. For clinicians, determining when to continue, pause, or permanently discontinue therapy often requires balancing limited evidence with individual patient circumstances.

In the latest episode of Oncology Unfiltered, Melissa Cutrona, Co-Founder and General Manager of i3 Health and Oncology Data Advisor, sits down with Matthew Hadfield, DO, Oncology Data Advisor Editor in Chief, to discuss the evolving challenges of long-term immunotherapy management, including immune-related adverse events, treatment fatigue, surveillance, and the need for shared decision making.

Recognizing the Broad and Variable Effects of Immunotherapy

Although immune checkpoint inhibitors are now widely used, their mechanisms of action and potential toxicities remain incompletely understood. Dr. Hadfield emphasized that adverse effects can be unpredictable and may initially appear subtle.

“Any change at all should send alarm bells that something could be wrong or developing that is a complication of the therapy that can easily be trivialized,” he said.

Symptoms such as fatigue, weakness, or depressive symptoms may be common among patients with cancer, but they can also indicate immune-related endocrine complications, including thyroid or adrenal insufficiency. Other toxicities, such as pneumonitis, may be difficult to distinguish from infection or disease-related symptoms.

Because immune-related adverse events can involve multiple organ systems and vary considerably from patient to patient, clinicians must maintain a high level of suspicion throughout treatment.

Understanding Why Resistance Develops

Checkpoint inhibitors work by removing inhibitory signals that cancer uses to evade immune attack. However, tumors can resist immunotherapy through multiple mechanisms.

Dr. Hadfield explained that cancer can create a hostile tumor microenvironment by making it acidic, fibrotic, or poorly accessible to immune cells. It may also alter blood flow and vascular structures to divert immune cells away from the tumor.

“Cancer exploits multiple ways to hide and evade from the immune system,” he said.

These mechanisms help explain why some patients experience durable responses while others have limited or no benefit from treatment. Responses can also vary significantly by tumor type. Dr. Hadfield noted that metastatic melanoma may have a substantial proportion of patients with long-term benefit, while certain prostate cancer populations have low response rates when specific tumor characteristics are absent.

How Long Should Treatment Continue?

One of the most challenging questions in immunotherapy is determining how long patients should remain on treatment. Unlike chemotherapy, which is often administered in defined cycles to allow recovery from toxicity, immunotherapy trials have used different treatment durations depending on the cancer type and study design.

“The reality is that there are some patients who have a complete response to their cancer from a checkpoint inhibitor and they likely don't need it anymore,” Dr. Hadfield explained. “And then there are patients who have stable disease from their therapy and can be on a checkpoint inhibitor for years.”

Some clinical trials have treated patients for one or two years, while others have continued therapy until disease progression or unacceptable toxicity. As a result, decisions about treatment duration often extend beyond the endpoint of the clinical trial and require individualized risk-benefit discussions.

Retreatment After Progression or Toxicity

Retreatment may be reasonable for some patients who experience limited progression after a prolonged response, but the decision depends heavily on the tumor type, prior response, and clinical context.

The question becomes more complicated when immunotherapy must be stopped because of severe toxicity. Although restarting treatment may offer continued anticancer benefit, it can also trigger recurrent or even more serious immune-related complications.

“It can be dangerous to restart the therapy again,” Dr. Hadfield said. “But if the patient was deriving benefit, there is certainly a potential detriment to not giving them that therapy anymore.”

In patients receiving adjuvant therapy after surgery, the potential benefit of retreatment may not outweigh the risks of severe toxicity. For patients with metastatic disease and few remaining treatment options, clinicians may consider retreatment more cautiously when the potential benefit is greater.

Balancing Treatment Benefit With Patient Burden

Treatment decisions are not based solely on imaging or laboratory results. Patients may experience substantial time, financial, emotional, and logistical burdens even when treatment-related side effects are limited.

“It's incredibly hard being a patient with cancer,” Dr. Hadfield noted. “Life doesn't stop, your finances, family obligations, everything that everyone is dealing with, but you also have to come in and get these treatments.”

For some patients, a treatment break may be preferable to permanent discontinuation. Others may wish to continue therapy as long as it appears effective and tolerable. These preferences should be incorporated into clinical discussions rather than assuming that all patients will value treatment continuation or discontinuation in the same way.

“At the end of the day, it really is having a genuine and honest conversation with the patient and figuring out what works best for them,” he said.

Supporting Patients During Treatment Breaks

Stopping treatment can provoke anxiety, particularly among patients who are in complete remission and fear that discontinuation will lead to recurrence. Surveillance imaging and circulating tumor DNA may help provide reassurance in appropriate clinical settings.

Dr. Hadfield explained that patients are not necessarily being abandoned when therapy ends. Instead, continued monitoring can identify suspicious changes or evidence of recurrence and allow treatment to resume when clinically appropriate.

Palliative care and supportive care specialists can also play an important role, particularly when fatigue or other symptoms threaten treatment adherence. Dr. Hadfield noted that immunotherapy can produce profound fatigue because of sustained immune activation, and supportive care interventions may help some patients remain on treatment more successfully.

Decisions Remain in the Gray Area

Immunotherapy management continues to involve substantial clinical judgment because many questions lack definitive answers. Some toxicities may be irreversible, including insulin-dependent diabetes, hypothyroidism, and adrenal insufficiency requiring long-term steroid replacement.

“We don't know who will and will not get toxicities, and we don't know how to balance that risk-benefit conversation,” Dr. Hadfield said.

For now, clinicians must communicate available evidence clearly, explain potential risks, and ensure that patients understand how treatment decisions may affect their lives.

“We're still in the infancy of checkpoint inhibitors,” he added. “We don't know the long-term consequences of patients that we cure with immunotherapy.”

Future advances in risk stratification and predictive biomarkers may help identify which patients are likely to respond, develop toxicity, discontinue treatment safely, or benefit from retreatment. Until those tools are available, personalized communication and multidisciplinary care remain central to responsible immunotherapy management.

Key Takeaways

Immunotherapy-related toxicities can be subtle, variable, and difficult to distinguish from common cancer symptoms.
Cancer can resist checkpoint inhibition through multiple mechanisms involving the tumor microenvironment and immune evasion.
The optimal duration of immunotherapy remains uncertain and varies by cancer type, treatment response, and trial design.
Retreatment after progression or severe toxicity requires an individualized risk-benefit assessment.
Treatment breaks, surveillance, supportive care, and patient preferences should be incorporated into long-term treatment planning.
Predictive biomarkers and improved risk stratification may eventually personalize treatment duration and retreatment decisions.

Immunotherapy Fatigue: Resistance, Retreatment, and When to Stop