Mrinali Dhembla was planning a wedding when the back pain started. She was 26, newly engaged, and working as a digital media strategist. For months, she dismissed early warning signs, including rectal bleeding, low-grade fevers, and chronic constipation. When a doctor finally delivered the news, she refused to believe it. “I still remember the doctor telling me that I had cancer, and my first instinct was to say that he was wrong,” Dhembla recalled. “I said, ‘That’s not possible. I’m just 26 years old.'”
She was wrong to doubt it. Dhembla had been diagnosed with stage 3 rectal cancer that had already spread to her spine. What followed was not the surgery, radiation, and chemotherapy that define the standard path through this disease. Instead, her doctors uncovered a genetic detail that unlocked a different option entirely, one that cleared her cancer in four months and left her body intact. “I was declared cancer-free in July of 2025, and I’ve taken three trips since then,” she told Good Morning America. Her story has become one of the clearest examples yet of what rectal cancer immunotherapy can accomplish when the biology lines up.
The Warning Signs She Dismissed – and the Diagnosis She Didn’t See Coming
Dhembla experienced significant pain and fatigue before her diagnosis. “I just thought my life was gonna end after months of aggravating back pain and fatigue,” she recalled. The symptoms she had attributed to ordinary life – bowel irregularities, minor fevers, fatigue – had a more serious cause. When Dhembla first heard the words “you have cancer,” she was shaken. “In your 20s, you think a little bowel disturbance isn’t serious – you assume you can just live through it,” she said.
Related Video:
This video from a leading cancer center explains how immunotherapy works to treat cancer, directly relevant to understanding Mrinali Dhembla’s treatment approach.
Her experience fits a broader and concerning trend. The incidence of young-onset colorectal cancer is rising globally. A study by American Cancer Society researchers confirms colorectal cancer is now the leading cause of cancer deaths in men and women younger than age 50. Data from the Journal of Medical Screening reported a 2.3% increase in rectal cancer cases among people in their 40s since the 1990s and a 1.3% increase in colon cancer cases among the same demographic in the same period. Dhembla sits at the younger edge of this trend, but her case is no longer an isolated anomaly.
The standard picture for a stage 3 rectal cancer diagnosis is grim. The standard treatment for stage 3 rectal cancer typically involves chemotherapy, radiation, and surgery. Stage 3 rectal cancer is classified as regional colorectal cancer. National Cancer Institute data shows a five-year survival rate of approximately 72% for this stage. Survival rates vary considerably within stage 3 depending on the substage – stage 3A carries a survival rate of around 89%, reflecting cases where cancer has spread to only a few nearby lymph nodes; stage 3B ranges between 69% and 80%, depending on tumor depth and lymph node involvement; and stage 3C, the most advanced form, carries a survival rate of approximately 53%, where the cancer has reached a larger number of lymph nodes.
For Dhembla, the stakes were even higher than those numbers suggest. Surgery carried severe, life-altering risks. She faced the possibility of complex spinal operations with potential neurological damage, or losing her rectum and requiring a permanent colostomy bag. But that path never happened, because her doctors found something in her genetics that changed everything.
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The Genetic Clue That Changed Her Treatment
When Dhembla’s medical team ran genetic tests, they found Lynch syndrome. Lynch syndrome is an inherited condition in which DNA replication errors are not automatically corrected by the body. Over time, these errors can accumulate and trigger cancer, as happened in Dhembla’s case. She had not known she carried the mutation. Dhembla did not know she had Lynch syndrome and had not undergone surveillance before her diagnosis, which came after she dismissed symptoms such as rectal bleeding, low-grade fevers, and constipation that turned chronic.
Lynch syndrome accounts for 3% to 5% of all colorectal cancers and is the most common inherited form of colorectal cancer, resulting from germline (inherited DNA) mutations in the DNA mismatch repair (MMR) genes, including MLH1, MSH2, MSH6, PMS2, and EpCAM. About one in 300 people carry a harmful genetic mutation that causes Lynch syndrome. The average age of onset of colon cancer in Lynch syndrome patients is between 40 and 60, well below the 67 to 71 average age in patients without a genetic predisposition. The Colorectal Cancer Alliance notes that among those with Lynch syndrome, between 30% and 74% will develop colorectal cancer over their lifetime.
What Lynch syndrome takes away in terms of cancer risk, it gives back in one specific way. Lynch syndrome makes tumors highly vulnerable to immunotherapy. The dual-immunotherapy drug regimen that treats these tumors won the 2018 Nobel Prize in Physiology or Medicine and is specifically designed for patients whose tumors are classified as “MSI-high.” MSI-high (microsatellite instability-high) is a description of a tumor’s genetic makeup – specifically, that its DNA repair system is broken, leaving thousands of mutations that the immune system can learn to target. Dr. Nicholas Hornstein, assistant professor of medical oncology at Northwell Health Cancer Institute, explained: “That means the tumor’s DNA repair machinery is broken, which is exactly what we see in Lynch syndrome.”
The catch is that very few rectal cancers carry this profile. According to Dr. Hornstein, “only about 15% of all colorectal cancers are MSI-high, though the proportion is higher in younger patients and in those with Lynch syndrome.” For patients who do have MSI-high tumors, that detail transforms the treatment conversation entirely.
How Immunotherapy Works for Colorectal Cancer
Immunotherapy is not chemotherapy. It does not poison cancer cells directly. Instead, it works by removing the brakes that tumors place on the immune system. To understand why this matters for a young adult cancer diagnosis like Dhembla’s, it helps to understand the mechanism.
Related Video:
This video addresses the specific challenges young adults face when diagnosed with cancer, relevant to Mrinali’s experience being diagnosed with stage 3 rectal cancer at 26.
PD-1, a co-inhibitory receptor, inhibits antigen-specific T cell proliferation through ligand binding. The PD-1/PD-L1 pathway is a primary mechanism that cancer cells use to escape T-cell immune surveillance. In plain terms: cancer cells wave a flag that tells immune cells to stand down, and immune checkpoint inhibitors (drugs that block this signal) strip that flag away. CTLA-4, expressed on the surface of T cells activated by tumor antigens, suppresses T cell activation when it binds to certain surface proteins. Monoclonal antibodies (lab-made proteins) that block these pathways exert anti-tumor effects by activating tumor-specific cytotoxic T lymphocytes and reactivating the immune system’s attack on cancer.
Dhembla received an invitation to try a dual-immunotherapy regimen consisting of two drugs called nivolumab and ipilimumab. Nivolumab (brand name Opdivo) targets the PD-1 pathway. Ipilimumab (brand name Yervoy) targets CTLA-4. Together they attack two different “off switches” in the immune response, blocking them simultaneously. Dhembla’s doctors selected her to be one of the first patients to receive this dual immunotherapy treatment, which worked by taking the brakes off her immune system so it could fight cancer cells.
“Patients that have Lynch syndrome are excellent candidates for immunotherapy,” Dr. Hornstein said. “Because they have so many mutations in their cancer cells, it allows their immune system to recognize them, and they just need a little bit of a boost with immunotherapy to become effective at eradicating their tumors.”
This approach draws directly on landmark clinical research. The CheckMate 142 trial, reviewed in a 2023 paper published in ScienceDirect’s Colorectal Cancer Immunotherapy review, found that the disease control rate for dual therapy with nivolumab and ipilimumab exceeded 80% in MSI-high colorectal cancer patients. The U.S. Food and Drug Administration approved this combination for advanced cancers including melanoma, mesothelioma, and colorectal cancer.
Can Immunotherapy Cure Stage 3 Rectal Cancer?
This is the question most people ask first. The honest answer: for a specific group of patients, the evidence is becoming hard to argue with.
The most striking clinical data comes from Memorial Sloan Kettering Cancer Center (MSK) in New York. Researchers there tested dostarlimab (brand name Jemperli), a different PD-1 inhibitor (a type of immune checkpoint drug that blocks the PD-1 off-switch), in patients with MSI-high, locally advanced rectal cancer. Dostarlimab achieved a 100% clinical complete response rate in a study of patients with locally advanced mismatch repair-deficient rectal cancer. That means every patient who completed treatment showed no detectable tumor. With a median follow-up of 17.9 months, all 42 patients who completed dostarlimab treatment had no evidence of tumors. For 24 patients with a median follow-up of 26.3 months, those complete responses held for at least a year.
Lead study author Dr. Andrea Cercek of Memorial Sloan Kettering reported: “cCRs are durable over two years, and no patients have required chemotherapy, radiation, or surgery.” Those results were presented at the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting and published in the Journal of Clinical Oncology.
The MSK work expanded further in 2025. A phase 2 trial update presented at the American Association for Cancer Research (AACR) Annual Meeting in April 2025 included 103 patients with stage 2 to 3 resectable mismatch repair-deficient cancers, with 49 patients in the rectal cancer cohort and 54 patients with non-rectal cancers. The results, simultaneously published in the New England Journal of Medicine, found that 80% of patients did not require surgery, radiation, or chemotherapy after six months of treatment with immunotherapy alone. Overall, 92% of patients in the rectal cancer cohort were still disease-free at two years, and four patients’ complete responses had lasted five years.
The U.S. Food and Drug Administration gave dostarlimab “Breakthrough Therapy Designation” for the treatment of this type of rectal cancer in December 2024. That designation is used when preliminary evidence suggests a drug offers substantial improvement over existing treatments for a serious condition.
So can immunotherapy cure stage 3 rectal cancer? For MSI-high tumors, the data suggests yes – at least for a meaningful proportion of patients. The critical qualifier is tumor biology. Patients whose cancers are not MSI-high currently see far weaker responses. Researchers are actively working to understand why and to expand these results to more patients.
Dhembla’s Treatment: What Actually Happened
Dual immunotherapy breaks through the tumor’s protective barriers and empowers the immune system to fight cancer cells. After only three infusions over four months, Dhembla’s scans and biopsies showed no evidence of disease. Her circulating tumor DNA (molecules released into the bloodstream by cancer cells) decreased from 300 to zero. Dhembla was declared cancer-free in July 2025.
The speed of that response reflects the precision of the match. When an MSI-high tumor meets the right immune checkpoint drug, the immune system can move fast. “Dhembla’s immune system did what surgery, chemotherapy and radiation may not have been able to do,” Dr. Hornstein noted, calling her case a profound example of precision medicine that matches the right treatment to the right biology. Precision medicine, in this context, means treating based on a tumor’s specific molecular profile rather than treating all rectal cancers the same way.
Immunotherapy spared Dhembla from months of debilitating chemotherapy and radiation treatments, and she even ran a 5K during her treatment period. That detail is not incidental. It speaks to a quality-of-life difference that oncologists now consider central to choosing between treatment paths. Current treatments like surgery, radiation, and chemotherapy can seriously affect quality of life. Treating rectal cancer this way can lead to infertility and problems with bowel, bladder, and sexual function, as well as other daily challenges.
The side effects of dual immunotherapy are real but different in character. They include fatigue, thyroid dysfunction, or inflammation of the gastrointestinal tract and lungs. “I take a pill for my hypothyroidism every morning, but it’s part of my routine now and doesn’t affect my day-to-day life,” Dhembla said. Hypothyroidism (underactive thyroid gland) is a known and manageable side effect of PD-1 inhibitors and is treated with a daily hormone replacement tablet.
What This Means If You or Someone You Know Has Rectal Cancer
Dhembla’s outcome is remarkable, but it hinges entirely on a specific tumor profile. Not every rectal cancer patient qualifies for this approach. Here is what the current evidence supports.
Ask About Biomarker Testing
The first and most important step for any rectal cancer patient is to request biomarker testing. This means testing the tumor tissue for MSI status (microsatellite instability) and MMR deficiency (mismatch repair deficiency, meaning the tumor’s DNA repair system is broken). Pembrolizumab, another PD-1 inhibitor, is strongly recommended as first-line therapy for MSI-high metastatic colorectal cancer. The MSI status and tumor mutation burden of the tumor must be clarified before starting treatment. If your oncologist has not mentioned biomarker testing, ask for it specifically.
Know the Lynch Syndrome Connection
If you have Lynch syndrome in your family history, tell your doctor before any cancer workup is complete.
Medical Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice because of something you have read here.