Although the standard treatment of head and neck cancers involves surgery followed by post-operative radiation, many cases can be treated with radiation and chemotherapy without the need for surgery. Advances in image-guided radiation therapy have allowed us to deliver more intense doses of radiation in a more focused area of the body, increasing the treatment’s effectiveness against cancer and minimizing its impact on surrounding structures, including critical structuers such as salivary glands, spinal cord, brainstem and swallowing muscles.
At City of Hope, we have been treating head and neck cancers using Helical TomoTherapy since 2004, and therefore our department has extensive experience in planning and delivering such treatment. This technology combines radiation delivery with advanced imaging - including positron emission tomography (PET), magnetic resonance imaging (MRI) and three-dimensional computed tomography (CT) scans - so that treatment is precisely targeted to the tumor, while avoiding nearby normal tissues. Post-treatment imaging is also performed during follow-up appointments to ensure optimal outcomes for the patient.
Here is an example: the upper left figure shows a traditional CT scan of the neck used for treatment planning. The borders of the tumor are poorly outlined. With a fused PET/CT treatment planning scan (upper right figure), one can immediately recognize the boundaries of the tumor volume. The scan also demonstrated small lymph nodes in the neck with brightness levels consistent with tumor involvement (lower left figure). With CT alone, these lymph nodes would not have been covered in the high-dose treatment volume. Given the seamless PET/CT image fusion, it was possible to delineate these nodes in the treatment plan without distortion or uncertainty. Furthermore, with a fused MRI of the neck (lower right figure), additional information regarding tumor extension is now available. This data is easily incorporated into our planning.
This figure shows the same patient’s Tomotherapy treatment plan: the color map displays different amounts of radiation dose being given to different areas within the head/neck. This is known as “dose-painting.” The distribution of radiation dose across the head/neck is customized to each patient’s individual tumor type and anatomy.
This process of sophisticated planning using the Tomotherapy system results in dose distributions that can avoid critical structures in the immediate vicinity of the tumor, such as the salivary glands (outlined in pink and light blue).