Studies Demonstrate Clinical Advantages of Proton Therapy

Proton therapy can be advantageous for certain types of cancer.
Proton therapy can be advantageous for certain types of cancer.

SAN ANTONIO, TX—The search for evidence to support the growing use of proton therapy for more cancers continues to uncover valuable findings. New data from clinical trials conducted demonstrate the technology's potential advantages over conventional radiation, including less side effects and survival in some cases, for several harder-to-treat tumors: pancreatic cancer, late-stage non-small cell lung cancer, and chordoma and chondrosarcoma, which are 2 rare cancers found in bone or soft tissue.

The research was presented at the 2015 American Society for Radiating Oncology (ASTRO) annual meeting.

The first study investigated the use of proton therapy in patients with pancreatic cancer whose cancer returned. Local recurrence occurs in nearly 25% of these patients following other treatments, such as chemotherapy, surgery, and radiation, and is associated with a very high morbidity.

Researchers looked at 15 patients with locally recurrent pancreatic cancer who were re-irradiated with proton therapy, 10 of whom were also on chemotherapy (5-fluorouracil or capecitabine-based). The median time since the original conventional radiation was 26.7 months. Most of the patients tolerated the radiation well, with minimal side effects. The median survival was 15 months and overall survival at 1 year was 71.5%. Local-regional progression-free survival and distant-metastatic-free survival at 1 year were 72% and 63.8%, respectively.

This more than doubles the median survival for re-irradiation with stereotactic body radiation therapy (SBRT), which is 6 to 8 months. Median survival in the study also far exceeded the historical survival of patients with unresectable disease treated with chemotherapy alone (approximately 9 months), which is the main treatment modality offered to patients with recurrent pancreatic cancer, the authors report.

Another study from Penn Medicine provides the first clinical report of proton therapy vs intensity modulated radiation therapy (IMRT) in the postoperative setting for late-stage non-small cell lung cancer (a total of 34 patients; 17 in each arm).

Radiation is typically given to these patients after surgery to remove a tumor; however, studies have shown that the toxicity of conventional radiation can outweigh its benefits. Proton therapy appears to be well-tolerated, while maintaining the positive clinical outcomes witnessed with IMRT, the authors reported.

Patients who underwent proton and IMRT had similar, excellent short-term outcomes: 1 year overall survival and local recurrence-free survival were 85.7% and 94.1% for proton and IMRT, respectively. Side effects occurred (2 patients had radiation pneumonitis and esophagitis in both sets of patients), but were less severe in the proton group.

A team from Penn Medicine also presented results from a prospective clinical of proton therapy for chordoma and chondrosarcoma. Chordoma is part of the sarcoma family, and occurs in the bones of the skull and spine, while chondrosarcoma is a type of bone cancer that begins in cartilaginous tissue. Both are rare, difficult cancers to treat.

Proton therapy, with its ability to deliver high doses of radiation while sparing healthy organs, has emerged as a preferred treatment for these patients. The standard of care is surgery followed by conventional radiation, but that treatment can fail.

The team studied 20 patients with nonmetastatic chordoma and chondrosarcoma who underwent proton therapy between 2010 and 2014. Of the patients, 10 had skull base chordomas, 5 had sacral chordomas, 3 had cervical spinal chordomas, and 2 had skull base chondrosarcomas.

The study yielded positive survival outcomes for the patients: local recurrence-free survival, distant metastases-free survival, and disease-free survival at 2 years were 92%, 95%, and 87%, respectively. All patients were alive at last follow up in February 2015. Some toxicities were reported in the patients, including fatigue, epistaxis, and gastrointestinal issues. That toxicity data is encouraging compared with historical results using conventional radiotherapy, the authors reported.

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