And that’s especially true for patients whose cancer develops in the same area where the first cancer had been successfully treated with radiation.

Physicians have a harder time using photon treatments a second time. They don’t want inadvertent radiation to re-injure adjacent tissues and organs — over and above the unintentional radiation experienced during photon treatments for the first cancer.

And if chemotherapy and surgery are poor treatment options, surviving the second cancer is more challenging.

But targeted proton beams offer an alternative radiation option that may increase the odds of surviving these locally recurring cancers and local secondary cancers.

Protons can provide effective cancer-killing power, with less collateral damage to adjacent tissues and organs, particularly those that have already been affected by inadvertent radiation during the first cancer treatment, said Anita Mahajan, MD, medical director of the MD Anderson Proton Therapy Center in Houston, Texas. “Protons are very strategic that way,” she said.

“When you treat a person for breast cancer with photons, you’re treating the whole anterior chest wall,” Mahajan said. “Sometimes, the heart gets some radiation dose. Years later, should that patient develop lung cancer, you can use protons to treat the cancer and avoid additional radiation to the heart. With protons, you can come in from the back and side and around the front part of the chest. You can actually think about ways to avoid radiation to areas where you don’t want radiation.”

Mahajan said she currently has four “re-radiation patients” receiving treatment at MD Anderson. Some were treated with photon radiation therapy 15 or 20 years ago and recently developed a second cancer in the same area.

Re-radiation cases include a patient treated successfully for Hodgkin’s Lymphoma who now has breast cancer and a patient treated successfully for breast cancer who has since developed lung cancer. “We have a 23-year-old woman with rhabdomyosarcoma,” Mahajan added. “She had chemotherapy and radiation four years ago. This time, she had surgery, chemotherapy and proton radiation.”

Radiation oncologists are very aware of the unintentional harm of photon radiation treatments, Mahajan said. “With tissue, there is a certain memory that occurs with radiation,” she said. “It goes through changes that make it much less tolerant to more radiation. If you talk to surgeons, they can tell the tissue that’s been irradiated years ago. It’s different. They can tell by feel and color. The tissue is not as pink and happy.”

Mahajan cautioned not to presume that all local secondary cancers or locally recurring cancers are caused by photon radiation.

“There are certain rules that need to be checked off before we can call it a radiation-associated tumor,” Mahajan noted. “It has to be in an area that received radiation therapy. It has to be a different type of tumor than the initial tumor treated. And it has to have occurred in the right timeframe. If a tumor develops a year or so after, it’s very, very unlikely it’s associated with radiation therapy. Usually, the secondary tumor develops at least five to seven years after.”