Proton radiation for treatment of cancer of the oropharynx: Early experience at Loma Linda University Medical Center using a concomitant boost technique

Proton radiation therapy for head and neck cancer

Due to the close spatial relationship of head and neck and skull base tumors to numerous normal anatomical structures, conventional photon radiation therapy can be associated with significant acute and long-term treatment-related toxicities. Superior dose localization properties of proton radiation therapy allow smaller volumes of normal tissues to be irradiated than is feasible with any photon technique. Intensity-modulated proton therapy (IMPT) is a powerful delivery technique which results in improved dose distribution as compared to that of intensity-modulated radiation therapy (IMRT). Initial clinical experience with proton radiation therapy in treatment of head and neck and skull base tumors is promising. Prospective multi-institutional trials are underway to define the role of proton radiation therapy, particularly IMPT, in the treatment of head and neck and skull base tumors.

Development and operation of the Loma Linda University Medical Center proton facility

The Proton Treatment Center at Loma Linda University Medical Center, the world's first hospital-based proton facility, opened in 1990 after two decades of development. Its early years were marked by a deliberately cautious approach in clinical utilization of protons, with intent to establish hospital-based proton therapy on a scientific basis. The facility was designed to be upgradeable, and development since 1990 has proceeded in three distinct phases of upgrades, both in technology and clinical applications. Upgrades continue, all of them based on an underlying program of basic and clinical research; future new applications of proton radiation therapy are expected to follow.

Hypopharyngeal cancer

Hypopharyngeal cancers are usually squamous cell carcinomas (SCCs) that has the worst prognosis among the head and neck cancers. Overall, 5-year survival rate remains poor despite recent improvements in diagnostic imaging, radiation and chemotherapy, and improved surgical techniques. Hypopharyngeal cancers tend to present with advanced primary disease, and nodal metastasis is highly likely. The most important features determining prognosis are the size and extent of local spread of the primary carcinoma and the extent of involvement of regional lymph nodes. Distant metastasis at presentation is more common in hypopharyngeal cancers than in other head and neck cancers. Poor survival rate is partly due to emergence of second primary cancers but also to development of distant metastasis. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) remain the mainstay of initial radiological evaluation of hypopharyngeal cancer. Imaging usually results in upstaging of the tumor at presentation. Meticulous evaluation of the extent of the primary tumor with attention to spread to the subsites of the hypopharynx, larynx, and cartilage invasion are necessary for accurate staging. After surgery and radiation therapy, it is difficult with CT and MR to differentiate residual and recurrent tumor from edema and scarring. Fluorine 18-fluoro-deoxy-glucose -positron emission tomography (FDG-PET) has high sensitivity in detection of occult, residual, and recurrent tumors but has low specificity. Combined PET and CT increase specificity and are increasingly being used to image posttreatment cases. Other newer imaging modalities such as diffusion-weighted imaging (DWI), MR spectroscopy, and MRI with superparamagnetic iron oxide (SPIO) contrast agent are reported to be useful and should be used more widely in difficult cases.

A systematic literature review of the clinical and cost-effectiveness of hadron therapy in cancer

BACKGROUND

In view of the continued increase in the number of hadron (i.e. neutron, proton and light or heavy ion) therapy (HT) centres we performed a systematic literature review to identify reports of the efficacy of HT.

METHODS

Eleven databases were searched systematically. No limit was applied to language or study design. Established experts were contacted for unpublished data. Data on outcomes were extracted and summarised in tabular form.

RESULTS

Seven hundred and seventy three papers were identified. For proton and heavy ion therapy, the number of RCTs was too small to draw firm conclusions. Based on prospective and retrospective studies, proton irradiation emerges as the treatment of choice for some ocular and skull base tumours. For prostate cancer, the results were comparable with those from the best photon therapy series. Heavy ion therapy is still in an experimental phase.

CONCLUSION

Existing data do not suggest that the rapid expansion of HT as a major treatment modality would be appropriate. Further research into the clinical and cost-effectiveness of HT is needed. The formation of a European Hadron Therapy Register would offer a straightforward way of accelerating the rate at which we obtain high-quality evidence that could be used in assessing the role of HT in the management of cancer.

Particle radiation therapy using proton and heavier ion beams

Particle beams like protons and heavier ions offer improved dose distributions compared with photon (also called x-ray) beams and thus enable dose escalation within the tumor while sparing normal tissues. Although protons have a biologic effectiveness comparable to photons, ions, because they are heavier than protons, provide a higher biologic effectiveness. Recent technologic developments in the fields of accelerator engineering, treatment planning, beam delivery, and tumor visualization have stimulated the process of transferring particle radiation therapy (RT) from physics laboratories to the clinic. This review describes the physical, biologic, and technologic aspects of particle beam therapy. Clinical trials investigating proton and carbon ion RT will be summarized and discussed in the context of their relevance to recent concepts of treatment with RT.

Future Issues in Highly Conformal Radiotherapy for Head and Neck Cancer

Improving the conformity of the radiation dose to targets in the head and neck promises reduced toxicity and, in some cases, potentially improved local-regional tumor control. Intensity-modulated radiotherapy (IMRT) is a method that allows highly conformal delivery of radiotherapy. In recent years, its use has spread rapidly in both academic and community radiation oncology facilities. The use of IMRT has raised multiple issues related to target definition, optimal treatment delivery methods, and the need to account for anatomic changes occurring during therapy. Some of these issues are reviewed in this article.

Radiotherapy for Head and Neck Cancer

The length and quality of head and neck cancer survivorship continues to improve. Radiotherapy has been central to this process through advances in treatment technology, fractionation schemas, radiosensitizing chemotherapy, and surgical technique. The future of head and neck radiotherapy looks brighter still with progress in radiosensitizing biologic therapy, molecular characterization, functional imaging, and rehabilitative strategies fast approaching. Head and neck cancer, a disease once fraught with nihilism and failure, is evolving into a major success story of multidisciplinary solid tumor management. Continued dedication and work on the part of provider and patient alike will be required to make this promise a reality.