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Radiation Treatments for Rectal Cancer

Radiation therapy alone or in combination with chemotherapy may be one of the first steps in treating rectal cancer for a large fraction of patients with newly diagnosed rectal cancer. Radiation therapy can be used to shrink a tumor before surgery, or to be used during surgery to kill off cancer cells and help prevent a recurrence of the cancer. In particular, radiation is recommended for patients with cancer that has spread to lymph nodes, or has spread beyond the wall of the rectum, as well as locally recurrent rectal cancers. Amol Narang, M.D., an associate professor of radiation oncology at Johns Hopkins and a member of the Rectal Cancer Multidisciplinary Clinic, notes that many studies have shown that radiation therapy along with surgery leads to fewer recurrences of rectal cancer than just surgery alone for these patients.

Patients in their child-bearing years may choose to meet with a fertility specialist before radiation therapy, as some treatments can be damaging to fertility. Our rectal cancer team can refer patients to these specialists before beginning their cancer treatment.

Imaging Rectal Cancer Before Treatment

Before radiation, chemotherapy or surgery for rectal cancer, imaging specialists may use one or more techniques to determine where the tumors are located in the rectum and how far they have spread into surrounding tissue and lymph node. These images help surgeons and radiation oncologists pinpoint exactly where to treat the cancer, how to remove as much of the cancer as possible so that the likelihood of the cancer returning is small, and how to preserve the muscles and nerves of the rectum to give a patient the best quality of life going forward.

Imaging techniques can include:

  • Rectal protocol MRI: this technique refers to MRI that includes images taken from specific angles to gain the best look at the rectum and surrounding tissue. These images are recommended for patients entering the Johns Hopkins Rectal Cancer Multidisciplinary Clinic.
  • Transanal ultrasound: transanal ultrasound (TRUS), sometimes called endorectal ultrasound (ERUS), creates images of the rectum from high-energy sound waves produced by a probe inserted through the anus.
  • Transanal endoscopy ultrasound: transrectal endoscopic ultrasounds (EUS), performed with a flexible endoscope inserted through the anus, are often preferred to transanal ultrasounds to view tumors higher in the rectum, closer to the colon.

Radiation treatments for rectal cancer may be delivered in small doses over five to six weeks of daily treatment, or they may be delivered in higher doses over a condensed time period of five days. Patients can work with their rectal cancer team to decide on which type of radiation therapy might be best to treat their particular cancer. For instance, a longer treatment time may offer more time for a tumor to shrink. This can be important for tumors near the anal sphincter, where a surgeon will want to remove as little tissue as possible to avoid the sphincter muscle and preserve natural bowel function. In other cases, the small intestine may be in the field of radiation for tumors that occur very high in the rectum, closer to the colon. Since the small intestine is very sensitive to radiation, an intense five-day course of treatment might not be the first choice for patients and their radiation oncology team.

The types of radiation treatments most commonly used for rectal cancer include:

  • External beam radiation: this type of radiation delivers a beam of high-energy x-rays to a patient’s tumor from outside the body. Radiation oncologists at Johns Hopkins may use intensity-modulated radiation therapy (IMRT), which delivers targeted doses of radiation in a pattern to match the shape of the tumor; or image-guided radiation therapy (IGRT), which uses images taken before and during the radiation delivery to guide the treatment. These techniques help the radiation oncologists focus radiation only on the tumor itself, and not healthy surrounding tissue.
  • Brachytherapy: Used less often than external beam radiation to treat rectal cancer, this radiation treatment is a targeted, high-dose treatment that is delivered directly in or near the tumor. Johns Hopkins is one of the only hospitals in the country to explore endorectal high-dose rate brachytherapy for rectal cancer, and a team of Johns Hopkins scientists are leading a clinical trial to study this further.
  • Intraoperative radiation therapy (IORT): intraoperative radiation therapy is delivered directly to a tumor site after the tumor has been removed during surgery. The treatment comes from a radioactive source fed through wires that are placed on the tumor. The technique may be used for a rectal tumor that has infiltrated muscles or bones in the pelvis, or in cases where rectal cancer has returned after a tumor was previously treated by radiation or surgery. Johns Hopkins radiation oncologists specialize in high-dose intraoperative radiation therapy for recurrent rectal cancer patients.
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