Pencil beam technology advances breast cancer treatment


Not all proton therapy is alike.

Recent technology developments have made delivery of protons more precise, making it an ideal treatment option for a much larger number of tumors. Breast cancer is top of the list.

That’s especially true at Provision Center for Proton Therapy, where more than 150 breast cancer patients have been treated since the center opened in 2014. That makes Provision one of the most experienced proton therapy centers in the country when it comes to treating breast cancer.

All of Provision’s treatment rooms are pencil-beam equipped, which allows physicians to very specifically and narrowly apply protons’ radiation power, sparing superfluous skin damage and, particularly important, significantly reducing tissue damage to the heart and lungs.

Among the breast ccases, most treatments, 64 percent, involved treating the breast and selected lymph node after a partial mastectomy and 28 percent after a complete mastectomy. A handful of cases have involved accelerated partial breast irradiation—a shorter, alternative treatment for earlier stage cancer—and treatment of both breasts without surgery. In one case, a patient had tissue expanders inserted after a mastectomy to prepare for reconstruction.

With pencil beam scanning, “we can provide whole breast treatment with proton therapy that delivers less dose than conventional radiation therapy to up to two-thirds of the skin,” says Niek Schreuder, Provision chief medical physicist. “And an additional advantage of pencil beam is in cases when the lymph nodes are treated. In these cases proton treatments improve heart and lung sparking drmatically compared to other treatment modalities. Unnecessary radiation to the cardiac system are now believed to be directly correlated to unwanted cardiac issues with toxicity after treatment.

Additionally, Schreuder says, Provision’s experience has shown that patients tolerate treatment well and are able to complete the treatment course without interruption and with minimal side effects such as radiodermatitis—a rash that can result from exposure to radiation.

Recent Advances in Clinical Proton Beam Therapy Exploiting the Benefits of Pencil Beam Scanning

Before pencil beam scanning technology was developed, doctors worked with a brass aperature combined with a wax or acrylic bolus or compensator, custom made for the patient, to shape and direct the beam of protons to the desired location of the tumor. However, this still provided an unwanted swath of protons radiating surrounding areas of the breast unnecessary for the patient’s cure—and resulting in undesirable side effects.

Pencil beam application, on the other hand, uses magnetic scanning to deliver individual spots of protons—more the size of a white board marker than a pencil, Schreuder says—to a cancer site, allowing for much more customization and precision in treatment plan.

The development of pencil beam delivery opened the door for proton therapy to become a viable alternative to conventional radiation for nearly all types of cancer, he says. Eighty percent of candidates for external beam radiation will receive a better dose distribution with proton therapy than with conventional x-ray therapy—up from an estimated 20-30 percent before the genesis of pencil beam scanning.

With breast cancer the number one cancer for women, that’s good news for patients seeking a treatment with less side effects and more promise of long-term health.