New clinical guideline on radiation therapy for rectal cancer

A new clinical guideline from the American Society for Radiation Oncology (ASTRO) provides guidance for physicians who use radiation therapy to treat patients with locally advanced rectal cancer. Recommendations outline indications and best practices for pelvic radiation treatments, as well as the integration of radiation with chemotherapy and surgery for stage II-III disease. The guideline, which replaces ASTRO's 2016 guidance for rectal cancer, is published in Practical Radiation Oncology.

Colorectal cancer is the second most common cause of cancer death in the U.S., and half of new colorectal cancer diagnoses are in people age 66 or younger. Rectal cancer diagnoses account for nearly one-third of colorectal cancers; an estimated 43,340 adults will be diagnosed with rectal cancer in 2020. While rectal cancer incidence and mortality rates have dropped among older adults in recent years, they have increased for those younger than age 55.

"As rectal cancer becomes more of a disease of younger adults, long-term survivorship and quality of life considerations become even more important. Part of our motivation was to create guidelines that provide options for different treatments that could potentially improve survival rates and also help preserve patients' quality of life," said Prajnan Das, MD, MPH, chair of the rectal guideline task force, and professor and chief of gastrointestinal radiation oncology at The University of Texas MD Anderson Cancer Center in Houston.

Standard treatment for locally advanced rectal cancer generally involves chemoradiation therapy or short-course radiation without chemotherapy, followed by tumor removal surgery and additional chemotherapy. More recently, several trials have shown potential for emerging paradigms, such as changing the sequencing of treatments or omitting portions of treatments for select patients.

"Different treatments are appropriate for different patients, and the oncology field at large is moving toward personalized care," explained Jennifer Y. Wo, MD, vice chair of the rectal guideline task force and associate professor of radiation oncology at Harvard Medical School and Massachusetts General Hospital in Boston. "Some patients may need less than what is considered a typical course of treatment, while some patients may need more. This guideline focuses on providing options that can be tailored to patients' characteristics and their wishes."

Recommendations in the guideline address patient selection for radiation therapy, delivery of pelvic radiation treatments, options for non-operative management of locally advanced rectal cancer and guidance for follow-up care. Key recommendations include:

• Neoadjuvant radiation therapy is strongly recommended for patients with clinical stage II-III rectal cancer to reduce their risk of locoregional recurrence. Radiation therapy for locally advanced rectal cancer should be performed before rather than after surgery. Radiation may be omitted in favor of upfront surgery for some patients at low risk of recurrence, after discussion by a multidisciplinary care team. Clinical staging involving a physical exam and pelvic MRI is critical to determine which patients should receive neoadjuvant radiation therapy.
• For patients who require neoadjuvant radiation therapy, both conventionally fractionated radiation and short-course radiation are recommended equally, given high-quality evidence for similar efficacy and patient-reported quality of life outcomes with each treatment. The guideline specifies optimal dosing, fractionation and delivery techniques for radiation therapy
• Recommendations address how to incorporate chemotherapy into the pre-operative setting for patients who are at high risk of recurrence and who would likely benefit from the additional treatment using a total neoadjuvant therapy (TNT) approach. Recommendations also address other sequencing and timing issues for radiation, chemotherapy and surgery, with specific attention to treatment tolerability and potential downstaging.
• Organ preservation approaches (i.e., non-operative management and local excision) may present an alternative to radical surgery for select patients, especially those who would have a permanent colostomy or inadequate bowel continence after surgery. The guideline outlines specific criteria for situations where surgery can be avoided, as well as long-term surveillance and care for these patients.

COVID-19 and Rectal Cancer

While the guideline was completed before the COVID-19 pandemic, recommendations can guide clinics as they continue to care for patients. To reduce how frequently patients needed to come into the clinic for treatment, many institutions across the country moved toward short-course radiation in the early months of the pandemic, which aligns with the guideline's recommendations.

"Patients usually complete short-course radiation therapy in one week, compared to five-and-a-half weeks for standard radiation treatment. That is particularly important in the COVID era, when you want to minimize patient time in the hospital and issues like financial toxicity are especially salient," said Dr. Das.

"We have yet to see the true impact of COVID-19, but we know that interruptions in screening likely will lead to fewer patients receiving treatment when their disease is more manageable," said Dr. Wo. "And if that does happen and we start seeing patients with more advanced disease, then the parts of the guidelines that specifically address treatment for high-risk patients will become even more important."