New Data Show TomoTherapy System Superior to RapidArc in Achieving Local Control of Head and Neck Cancers

Tomo Therapy System

Accuray Incorporated (NASDAQ: ARAY) announced today that a prospective study conducted at 14 French centers showed the clinical benefits of intensity-modulated radiation therapy (IMRT) delivered using the TomoTherapy System over volumetric modulated arc therapy with RapidArc radiotherapy technology for patients with head and neck cancer.

At 18 months, the local control rate and cancer-specific survival rate were significantly better in the TomoTherapy patient group than in the RapidArc group. The study, the first to prospectively compare clinical outcomes across radiation therapy platforms, was published online on June 26, 2017 in the peer-reviewed International Journal of Radiation Oncology – Biology Physics .

The TomoTherapy System is the only radiation system specifically designed for image-guided IMRT. Its TomoHelical™ Mode, used in this study, provides continuous delivery of radiation beams from 360 degrees around the patient, facilitating the treatment of the entire spectrum of head and neck tumors, regardless of shape or size or nodal involvement.

Jean-Emmanuel Bibault, MD, MSc, Department of Oncology and Radiotherapy, Georges-Pompidou European Hospital, Paris said, “This is the first study to assess whether the method of delivering IMRT impacts the results we are able to achieve. In previous studies, we showed that TomoHelical was able to deliver radiation dose distributions which precisely conformed to the shape of the tumor with steep radiation fall-off outside the target.”  He added, “In this new study, we showed in a prospective, but not randomized manner, that this had a significant clinical impact. Precision and accuracy are especially important when treating head and neck tumors, where dose outside the desired target may result in damage to critical structures such as salivary glands, vocal cords, the spinal cord or brainstem. These results should be further explored in a randomized trial.”

The study titled, “Clinical outcomes of several IMRT techniques for patients with head and neck cancer: A propensity score weighted analysis,” provides results for 166 patients. It demonstrated:

  • The TomoTherapy System’s unique ring-gantry based architecture and fast multileaf collimator, combined with its daily 3D image guidance, enabled clinicians to deliver a highly conformal and more homogeneous dose, contributing to better local control and cancer-specific survival rates compared to RapidArc
    • Further analysis suggests an even greater benefit in the local control of larger tumors and those that have spread to a high number of lymph nodes
  • Treatment with TomoHelical also enabled delivery of significantly reduced doses outside the tumor, leading to better acute salivary function than with RapidArc
    • Mouth dryness assessed by the treated patients was worse in the RapidArc group
    • Salivary disorders were more frequent in the RapidArc patient group

Fabienne Hirigoyenberry-Lanson, VP Global Medical and Scientific Affairs of Accuray. notes, “This landmark study demonstrates that the technique used to deliver IMRT can have a major impact on patient outcomes. Two key measures – the local control rate and cancer-specific survival rate – reinforce the TomoTherapy® System’s effectiveness in managing head and neck tumors, results we would also expect to see with the Radixact™ System, our next-generation TomoTherapy platform. And, importantly, salivary function was compromised after treatment in significantly fewer patients treated with TomoTherapy, even while they achieved better tumor control.”

About the Study

Fourteen institutions evaluated 166 patients in this prospective comparative study; 74 were treated using the TomoTherapy® System and 92 using RapidArc. Randomization was not possible because of unavailability of equipment. Inverse probability of treatment weighting (IPTW) using the propensity score analysis was undertaken to adjust for potential bias due to non-randomization. Even before the adjustment the TomoTherapy platform results were better than RapidArc as measured by local control, cancer-specific survival and salivary function, even though significant differences in several pre-treatment characteristics may have placed the TomoTherapy group at a disadvantage. Loco-regional control, specific and overall survival assessed 18 months after treatment were evaluated, as well as long-term toxicity and salivary function.

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