Memorial Sloan Kettering Cancer Center (MSK) presented new research on a range of important topics at the 2025 Annual Meeting of the American Society for Radiation Oncology (ASTRO), held September 27 to October 1 in San Francisco.
The presentations included two clinical trials — one for throat cancer and one for breast cancer — that looked at the benefits and effects of lowering radiation doses. Another research study compared intensity-modulated radiation therapy with proton therapy in patients with a variety of head and neck cancers.
In Patients With HPV-Positive Throat Cancer, Lowering the Radiation Dose Minimizes Damage to Immune System
Combined chemotherapy and radiation therapy is a common treatment for people with HPV-positive head and neck cancers, including oropharyngeal (throat) cancer, but doctors have observed that this treatment can weaken the immune system. Researchers decided to look at whether reducing the dose of radiation or chemotherapy that patients receive could protect the immune system.
A team led by radiation oncologist and early drug development specialist Nadeem Riaz, MD, MSc, retrospectively studied patients participating in two clinical trials focused on reducing treatment. Lower-dose radiation treatments are being studied as a way to help patients avoid the side effects of more intense treatments. In this analysis, the researchers wanted to determine how the reduced treatment impacted the level of immune cells in the patients’ blood.
They studied blood samples from 204 patients being treated for throat cancer. The team found that patients who received radiation to a larger area had a bigger drop in their immune cells, especially white blood cells. It also took much longer for these patients’ immune systems to recover — sometimes months or even years. By contrast, patients who had radiation only to the main tumor and not the surrounding area recovered much faster. Additionally, researchers found giving patients extra chemotherapy caused less damage than giving them a bigger dose of radiation.
“These findings suggest that giving less dose-intense radiation treatments for HPV-positive throat cancers can protect the immune system and help patients recover healthy immune function more quickly,” Dr. Riaz says. “This is something we plan to continue studying.”
For Patients With Early-Stage, Intermediate-Risk Breast Cancer, a Shorter Course of Radiation Therapy Prevents Disease Recurrence
A team of researchers led by radiation oncologist Atif Khan, MD, MS, found that a course of radiation therapy that lasted only three days, rather than the typical three to four weeks, appears to be safe and effective in women with breast cancer that is early stage but considered to be at higher risk of coming back.
The phase 2 trial focused on a type of treatment called accelerated partial breast irradiation (APBI), which uses precise radiation beams to kill cancerous cells in a smaller area of the breast than other types of radiation therapy. It is given to patients after surgery to prevent the cancer from coming back by cleaning up cells that may have been left behind.
The trial enrolled 145 patients, including 65 considered to be at intermediate risk of recurrence based on their age or the characteristics of their disease. All patients received three doses of APBI over a one-week period.
The study found that of patients in the intermediate-risk group who had been followed for at least three years (37 patients), no one’s cancer came back in the breast or a nearby area and only one patient had the cancer spread to another part of the body. As for side effects, one patient reported serious breast pain that could be related to treatment. A few others had moderate side effects, including pain and thickening of the tissue.
“This shortened treatment appears to be safe and easy for patients to tolerate,” Dr. Khan says. “We plan to expand this research to include more patients in the intermediate risk group. We also will collect additional data on the cosmetic results of the treatment.”
Proton Beam Radiotherapy Is Superior to IMRT People With Head and Neck Cancer
An MSK-led clinical trial that compared proton beam radiotherapy with intensity-modulated radiotherapy (IMRT) in patients with head and neck cancers found that proton beam therapy is just as effective as IMRT at controlling the disease, while causing fewer side effects.
The phase 2 multicenter study was designed and led by MSK radiation oncologist and early drug development specialist Nancy Lee, MD. It included 98 patients: 60 with parotid/salivary gland tumors, 27 with skin cancers, and 11 with tonsil cancers. The patients were randomized to receive either IMRT or proton beam therapy.
The primary purpose of the study was to compare physician-reported rates of mucositis (inflammation of the mucus membranes), but it also looked at other physician-reported side effects, patient-reported outcomes, rates of recurrence and metastasis, and overall survival. The researchers found that severe mucositis in the proton group was 7.5%, significantly lower than the 22.2% observed in the IMRT group. Other side effects, which included mouth and throat soreness, skin burns, and skin darkening, were also worse in the IMRT group. Importantly, there were no significant differences in how well the two treatments controlled the disease.
“Taken together, this data shows that proton beam radiotherapy can achieve disease control and survival comparable to IMRT with less acute toxicity and may offer an improved quality of life to patients with a range of head and neck cancers,” says Edward Christopher “Chris” Dee, MD, a graduating radiation oncology resident at MSK, who presented the results.