Radiation therapy might not be necessary for treating some forms of rectal cancer and lymphoma, sparing patients from the toxic treatment, a pair of new clinical trials show. One trial found that rectal cancer patients whose tumors shrink in response to chemotherapy can safely skip the radiation therapy that’s normally provided before surgery, researchers reported at the 2025 American Society of Clinical Oncology (ASCO) annual meeting in Chicago.
“We can successfully de-escalate treatment of rectal cancer and achieve the same high cure rates — keep patients disease-free with less long-term toxicity,” said lead researcher Dr. Deb Schrag, chair of medicine at Memorial Sloan Kettering Cancer Center in New York City.
In the second trial, the researchers determined that some people with lymphoma whose cancers respond to chemotherapy and immunotherapy don’t necessarily need radiation treatment. Radiation therapy is often used to kill cancer cells or slow their growth, but it also damages lots of healthy cells. As a result, it can have dire long-term health consequences for patients.
For example, radiation treatment can lead to a variety of heart problems later in life, said Dr. Julie Gralow, ASCO’s chief medical officer. “We cure these patients, they are radiated in their mid-30s, and then when they’re 50 they start having substantial cardiac problems from that radiation,” Gralow said. “So they’re looking at, can we omit the radiation and keep the same excellent long-term survival?” Gralow continued. “In these cancers where we’re doing well with other treatments, the question is, can we back off on radiation and improve the side effects for the patients? Can we treat with less?”
In the case of rectal cancer, radiation delivered to the pelvis can damage bowel, bladder and sexual function, and increase a patient’s future risk of pelvic fracture, Dr. Schrag said at an ASCO media briefing on Saturday. Additionally, “it can cause infertility and premature menopause, which is a big deal because we are seeing increasing diagnoses of rectal cancer in people before the age of 50,” Dr. Schrag explained. Globally, there are about 800,000 new rectal cancer diagnoses expected in 2023, with about 48,000 occurring in the United States, Dr. Schrag said.
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Typical standard care for locally advanced rectal cancer involves a five-and-a-half-week round of radiation therapy to the pelvis, followed by surgery and then four months of chemotherapy, Dr. Schrag said. This clinical trial shook up that process. Randomly assigned patients underwent chemo first, and if their tumors shrank, they went straight to surgery with the option of more chemo after. Patients who didn’t respond to the initial chemo in this group were given radiation therapy before surgery.
“What really motivated us is that there’s been so much progress since radiation became the standard of care — better chemotherapy, better surgical technique, more screening — so we’re finding more tumors when they’re smaller and easier to treat, better imaging so we can separate the good ones from the really bad ones,” Dr. Schrag said. “So we asked the question, could we use radiation more selectively and only give it for people who don’t respond to chemotherapy, rather than giving the radiation to everyone as part of the standard [treatment]?”
For the study, 585 patients underwent this new regimen, while another 543 received the standard course of care. It turned out that disease-free survival was about the same in both groups — about 81 percent in the chemo-and-surgery group versus about 79 percent in the radiation group. Further, more than 9 out of 10 patients in the chemo-and-surgery arm responded to chemotherapy and didn’t require any radiation at all, the results showed. “Importantly, only nine percent of patients in the intervention arm ended up needing the radiation,” Dr. Schrag said.
Dr. Pamela Kunz, director of the Center for Gastrointestinal Cancers at Smilow Cancer Hospital and Yale Cancer Center in New Haven, Conn., said the rectal cancer clinical trial is “practice-changing.” “What’s important here is that radiation can be safely omitted in many patients with locally advanced rectal cancer,” Dr. Kunz said at the ASCO briefing. “This is really ‘less is more.’ And the study shows that we can spare select patients from receiving radiation without compromising efficacy. This leads to improved quality of life and reduced side effects, including things like early menopause and infertility.”
The lymphoma clinical trial involved 268 patients whose imaging scans showed that their cancer responded well to chemo and immunotherapy. They all had primary B-cell lymphoma, an aggressive cancer that occurs more often in young adults. About half were also randomly assigned to receive radiation therapy, while the other half were observed to see if the radiation was unnecessary. Patient survival without the cancer progressing was about the same between both groups after 30 months — 98.5 percent in the radiation group and 96.2 percent in the observation group. Overall, patients in complete remission had a 99 percent overall survival rate at 30 months, regardless of whether they received radiation, the researchers said.
“This means that these patients can safely forgo radiation and its side effects without compromising survival,” ASCO expert Dr. Corey Speers said in a news release. Results from the rectal cancer trial were also published in the New England Journal of Medicine and the Journal of Clinical Oncology, alongside the ASCO presentations.
Radiation therapy remains a critical aspect of cancer treatment and can be lifesaving for many patients. But it can also affect healthy tissue surrounding a tumor, leading to both short- and long-term side effects. Depending on the treatment area, patients may experience bowel or bladder problems, sexual dysfunction, fatigue, infertility, or premature menopause. In certain cases, radiation to the chest can increase the risk of heart disease years after treatment.
This is why researchers are increasingly exploring whether some patients can safely receive less radiation without compromising their chances of a cure. The findings presented at ASCO suggest that, for carefully selected patients whose cancers respond well to chemotherapy or immunotherapy, avoiding radiation may help preserve quality of life while maintaining excellent outcomes.
RELATED: Probiotics May Be Useful During Radiation Therapy to the Prostate
While these studies did not specifically analyze outcomes by race, the findings may be particularly meaningful for Black patients. Black Americans continue to experience disparities in cancer diagnosis, treatment, and survival. Expanding access to multidisciplinary cancer care can help ensure eligible patients are considered for newer treatment approaches that may reduce long-term side effects without compromising.
For younger adults diagnosed with rectal cancer, avoiding unnecessary radiation may also preserve fertility and reduce treatment-related complications that can affect quality of life.
Please note that findings presented only at medical meetings should be considered preliminary until published in a peer-reviewed journal. It’s important to note that every person reacts differently to treatment.
If you develop side effects, it will depend on the type and location of your cancer, the dose of radiation being given, and your general health. Some people may develop few or no side effects, while others have quite a few, according to the American Cancer Society.
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