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• Posted June 6, 2023

Can Some Cancer Patients Safely Skip Radiation Therapy? New Studies Say Yes

Radiation therapy might not be necessary in treating some forms of rectal cancer and lymphoma, sparing patients from the toxic treatment, a pair of new clinical trials shows.

One trial found that rectal cancer patients whose tumors shrink in response to chemotherapy can safely skip the radiation therapy that's normally provided prior to surgery, researchers reported at the 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, 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,"Schrag explained.

Globally, there are about 800,000 new rectal cancer diagnoses expected in 2023, with about 48,000 occurring in the United States, Schrag said.

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, 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 prior to 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 out the good ones from the really bad ones,"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% in the chemo-and-surgery group versus about 79% in the group treated with radiation.

Further, more than nine out of 10 patients in the chemo-and-surgery arm responded to the chemotherapy and didn't wind up requiring any radiation at all, the results showed.

"Importantly, only 9% of patients in the intervention arm ended up needing the radiation,"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,"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 suffered from primary B-cell lymphoma, an aggressive cancer that occurs more often in young adults.

About half were randomly assigned to also receive radiation therapy, while the other half were simply 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% in the radiation group and 96.2% in the observation group.

Overall, patients in complete remission had a 99% 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 also were published in the New England Journal of Medicine and the Journal of Clinical Oncology, alongside the ASCO presentations.

Findings that are only presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.

More information

The American Cancer Society has more about radiation therapy side effects.

SOURCES: Deb Schrag, MD, MPH, chair, medicine, Memorial Sloan Kettering Cancer Center, New York City; Julie Gralow, MD, chief medical officer, American Society of Clinical Oncology; Pamela Kunz, MD, director, Center for Gastrointestinal Cancers at Smilow Cancer Hospital and Yale Cancer Center, New Haven, Conn.; New England Journal of Medicine, June 4, 2023; Journal of Clinical Oncology, June 4, 2023