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Alliance Study Shows Some Patients with Locally Advanced Rectal Cancer Can Safely Avoid Radiation Therapy

June 5, 2023

Patients with locally advanced rectal cancer with tumors that respond to chemotherapy can safely forego radiation therapy before surgery based on the findings of the phase III Alliance PROSPECT (N1048) trial presented at the 2023 Annual Meeting of the American Society of Clinical Oncology (ASCO) and simultaneously published in the New England Journal of Medicine (efficacy) and the Journal of Clinical Oncology (patient reported outcomes) on June 4, 2023. Omitting radiation therapy can reduce short- and long-term side effects that impact quality of life while providing similar outcomes in disease-free survival and overall survival.

“Having this [treatment] option is important for several reasons. First, in many parts of the world, radiation therapy is not readily accessible. An all-chemotherapy approach may make curative-intent treatment accessible for patients in these resource-constrained settings,” said lead study author Deb Schrag, MD, MPH, Chair of the Department of Medicine and George J. Bosl Chair at Memorial Sloan Kettering Cancer Center. “Additionally, given the rising rates of colorectal cancer in young patients, this provides an option for patients who wish to preserve fertility or avoid early menopause.”

In recent decades, treatment advances and early detection for colorectal cancers have led to a steady decrease in the risk of death from these diseases. However, the number of people being diagnosed is increasing, especially among younger adults. Radiation therapy to treat rectal cancer has short-term and long-term side effects that negatively impact quality of life, including fertility problems, the need for an ostomy, diarrhea and inability to control bowel movements, and bladder problems.

Researchers wanted to learn if using chemotherapy alone would be as effective as chemoradiation before surgery. The study included 1,194 people whose median age was 57, and about one-third (34.5%) were women. The median is the midpoint, meaning half the patients were younger than 57 and the other half were older than that. All participants were diagnosed with rectal cancer that had spread to nearby tissue or lymph nodes and could have chemotherapy and radiation therapy before a surgery called a low anterior resection with total mesorectal excision. During this surgery, parts of the rectum, bowels, and surrounding fatty tissue are removed. The participants were randomly divided into 2 groups, and 1,128 patients went on to receive treatment in this study.

In the first group, 543 participants received a chemoradiation treatment with a combination of radiation therapy and chemotherapy called 5FUCRT. In the second group, 585 participants received a chemotherapy combination called mFOLFOX6, and then their tumor was restaged, or reevaluated by the cancer care team. If the tumor shrank by 20% or more after chemotherapy, no radiation therapy was given before that person’s surgery. If the tumor did not shrink by 20% or more, radiation therapy was given before surgery. In this group, 53 people (9%) needed radiation therapy before surgery because their tumors did not shrink by 20% or more.

When comparing the two groups, there was not a significant difference in outcomes.

  • The disease-free survival rate was 78.6% in the first group that received chemoradiation and 80.8% in the second group that received mFOLFOX6 with added radiation therapy when needed.
  • Overall survival was 90.2% for the first group and 89.5% in the second group.
  • Surgical resection rates, or the complete removal of the tumor and surrounding tissue, was done in 97.1% of patients in the first group and 98.9% of patients in the second group.
  • Pathologic complete response, which is no sign of cancer cells in tissue after treatment, was 24.3% in the first group and 21.9% in the second group.

The results of this study show that it is safe and effective to treat locally advanced rectal cancer with preoperative chemotherapy and the selective use of chemoradiation therapy rather than treating all patients with chemoradiation. This study gives patients a new care standard that has the potential to reduce toxicities, such as preserving fertility. This is also important on a global scale, because access to radiation therapy is limited in some countries.

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