Which Cancers Respond Best to Immunotherapy Today?

Cancer immunotherapy — checkpoint inhibitors, CAR T-cell therapy, and related approaches — has produced some of oncology's most durable success stories, but its benefits are far from evenly distributed. Some cancers, like melanoma and certain lymphomas, now have decades-long survival data behind FDA-approved immunotherapies with response rates that would have been unthinkable twenty years ago. Others, including pancreatic cancer and microsatellite-stable colorectal cancer, remain largely resistant despite years of clinical trials. This article walks through where immunotherapy has its strongest, best-documented track record in 2026, the biology that explains why some tumors respond and others don't, and where the field is still searching for answers.

Hot Tumors, Cold Tumors, and Why Response Varies So Much

The single biggest predictor of whether a cancer responds to checkpoint inhibitors is whether it's biologically "hot" or "cold." Hot tumors are already infiltrated by T-cells and often carry a high tumor mutational burden (TMB) — meaning their cells display more mutated proteins ("neoantigens") that the immune system can recognize as foreign. Cold tumors, by contrast, have little immune cell infiltration, low mutational burden, and often actively suppress the immune cells that do arrive. Checkpoint inhibitors work by releasing the "brakes" (like PD-1/PD-L1 or CTLA-4) that tumors use to blunt T-cell attack — but if there's no meaningful T-cell presence to begin with, releasing the brakes accomplishes little. PD-L1 expression on tumor cells is used clinically as a rough biomarker for this hot/cold distinction, most notably in lung cancer, though it is an imperfect one. Reviews in the oncology literature describe an active area of research into "turning cold tumors hot" through combination strategies, underscoring that this is still very much an unsolved problem for a large share of cancers.

Melanoma: The Original Immunotherapy Success Story

Advanced melanoma is where checkpoint inhibitors first proved their power, and it remains the strongest, longest-tracked example. In the pivotal CheckMate 067 trial, patients with advanced melanoma treated with combination nivolumab plus ipilimumab reached a 10-year overall survival rate of 43%, compared with 37% for nivolumab alone and 19% for ipilimumab alone — with melanoma-specific survival even higher, at 52% for the combination. Median overall survival with the combination reached nearly six years (71.9 months), versus under two years for ipilimumab alone. This is genuinely rare in oncology: a decade of follow-up showing that a meaningful share of patients with what used to be a rapidly fatal diagnosis are still alive and, in many cases, effectively cured. That said, these are still minority outcomes — well over half of patients on combination therapy did not reach the 10-year mark, and the combination carries a substantially higher rate of serious immune-related side effects than either drug alone.

Non-Small Cell Lung Cancer: Response Tracks PD-L1 Expression

In non-small cell lung cancer (NSCLC) with high PD-L1 expression (tumor proportion score ≥50%), pembrolizumab has shown a durable survival advantage over chemotherapy. In the KEYNOTE-024 trial's five-year follow-up, 31.9% of pembrolizumab-treated patients were alive at five years, compared with 16.3% on chemotherapy — roughly double the long-term survival rate, in a disease where five-year survival was historically in the single digits for metastatic patients. This makes PD-L1-high NSCLC one of the clearer wins for biomarker-guided immunotherapy. Response is far less consistent, however, in PD-L1-low or PD-L1-negative NSCLC, where checkpoint inhibitors are typically combined with chemotherapy rather than used alone, and outcomes are more modest.

Blood Cancers: Where CAR-T and Checkpoint Blockade Shine Brightest

Two blood cancer categories stand out for exceptionally strong immunotherapy data. In relapsed/refractory classical Hodgkin lymphoma, PD-1 blockade produces some of the highest response rates seen anywhere in oncology — trials of nivolumab reported an 87% overall response rate (20% complete response), and pembrolizumab trials reported around 65% overall response (16% complete response); reviews describe Hodgkin lymphoma as showing greater than 70% overall response to PD-1 blockade generally, far above most solid tumors. In refractory large B-cell lymphoma, CAR T-cell therapy (axicabtagene ciloleucel) has shown similarly striking results: the pivotal ZUMA-1 trial reported an 82% objective response rate with a 54% complete response rate, and five-year follow-up data showed a 58% complete response rate with 42.6% of patients still alive at five years — remarkable in a population of heavily pretreated patients who had exhausted standard options. CAR-T is not without serious risks (cytokine release syndrome and neurotoxicity among them), and it remains a complex, specialized therapy — but for the subset of lymphoma patients who qualify, it has genuinely changed what "refractory" means.

Renal Cell Carcinoma: Durable, if Partial, Benefit

In advanced renal cell carcinoma, the combination of nivolumab and ipilimumab (studied in CheckMate 214) produced a 39% overall response rate and a 12% complete response rate in intermediate/poor-risk patients, with a median duration of response reaching roughly 76 months in long-term follow-up — meaning that for the minority who do respond deeply, remissions can last years. This has made checkpoint-inhibitor combinations a standard first-line option for many patients with advanced kidney cancer, though the majority of patients do not achieve a complete response.

MSI-High/dMMR Tumors: A Tumor-Agnostic Breakthrough

One of the most conceptually important moments in immunotherapy history came in May 2017, when the FDA granted pembrolizumab its first-ever tissue/site-agnostic approval — for any solid tumor with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) status, regardless of where the cancer originated. This approval was based on an objective response rate of 39.6% across 149 patients spanning 15 different cancer types, with 78% of responses lasting six months or longer. It mattered less because of the response rate itself and more because it established that a genomic biomarker could predict immunotherapy benefit better than the tissue of origin. MSI-H/dMMR status appears in a minority of several cancer types, including some colorectal, endometrial, and gastric cancers.

The Cold Tumors: Where Immunotherapy Still Struggles

Not every cancer has followed this trajectory, and honest reporting requires saying so plainly. Pancreatic cancer is the textbook example of a cold tumor — dense, immunosuppressive stroma and low mutational burden mean checkpoint inhibitors alone have shown limited activity. Microsatellite-stable (MSS) colorectal cancer — which accounts for roughly 85% of colorectal cancer cases — is similarly resistant; published reviews state plainly that single-agent checkpoint blockade is "generally ineffective" in this setting. Prostate cancer has likewise been characterized in the literature as an immunologically cold tumor with generally poor single-agent checkpoint-inhibitor response, though researchers are actively investigating combination approaches and biomarker-selected subgroups that may respond better. These aren't failures of the concept of immunotherapy — they're a reminder that its benefit is not universal.

Bottom Line

Immunotherapy has delivered some of the most genuine, durable advances in modern oncology — but which cancers benefit, and how much, varies enormously, and no source available today supports treating it as a uniform or guaranteed solution. If you or a loved one is considering immunotherapy, the most useful questions to bring to an oncologist are specific ones: What is my tumor's PD-L1 expression, tumor mutational burden, or MSI/dMMR status, and does that make me a stronger or weaker candidate for this approach? What is the actual, published response rate for my specific cancer type and stage — not immunotherapy in general? What happens if I don't respond, and what immune-related side effects should I watch for? For cancers like melanoma, Hodgkin lymphoma, and refractory large B-cell lymphoma, the evidence for meaningful, sometimes years-long benefit is strong. For cancers like pancreatic, MSS colorectal, and prostate, current evidence supports realistic expectations and close attention to whether a clinical trial or biomarker-selected combination approach might be more appropriate.