Basics of particle therapy II biologic and dosimetric aspects of clinical hadron therapy

Optimal modality selection in external beam radiotherapy

The goal in external beam radiotherapy (EBRT) for cancer is to maximize damage to the tumour while limiting toxic effects on the organs-at-risk. EBRT can be delivered via different modalities such as photons, protons and neutrons. The choice of an optimal modality depends on the anatomy of the irradiated area and the relative physical and biological properties of the modalities under consideration. There is no single universally dominant modality. We present the first-ever mathematical formulation of the optimal modality selection problem. We show that this problem can be tackled by solving the Karush-Kuhn-Tucker conditions of optimality, which reduce to an analytically tractable quartic equation. We perform numerical experiments to gain insights into the effect of biological and physical properties on the choice of an optimal modality or combination of modalities.

Primary adenoid cystic carcinoma of the trachea: clinical outcome of 38 patients after interdisciplinary treatment in a single institution

Background

Primary adenoid cystic carcinomas (ACCs) of the trachea are rare tumors of the central bronchial system. In patients presenting with unresectable tumors, severe comorbidities, or incomplete surgical resection, definitive radiotherapy is currently the recommended treatment. Irradiation with carbon ions (C¹²) has shown promising local control (LC) and survival rates in cases of ACCs of the head and neck. No data on the therapeutic efficacy of C12 radiotherapy in treating tracheal ACC has been published.

Methods

All patients with histologically confirmed ACC of the trachea treated with surgery and/or radiation treatment at Heidelberg University Hospital between 1991 and 2017 were included in this analysis. Patient and treatment characteristics, short- and long-term toxicity after radiotherapy, overall survival (OS), freedom from local progression (FFLP), and freedom from distant progression (FFDP) were prospectively acquired and retrospectively analyzed.

Results

Thirty-eight patients (23 women and 15 men) with a median age of 51 were treated by surgery (n = 20) and/or radiotherapy with either C¹² (n = 7) or photons (n = 24). Of these patients, 61% presented with locally advanced (stage 4) ACC. The median follow-up for all patients was 74.5 months. The 5-year OS for all patients was 95% (10-year: 81%). The 5-year FFLP and FFDP were 96% (10-year: 83%) and 69% (10-year: 53%), respectively. In patients who underwent surgery alone, the 5-year OS was 100% (10-year: 80%). The 5-year FFLP and FFDP were 100% (10-year: 100%) and 80% (10-year: 60%), respectively. In patients who underwent radiotherapy alone, the 5-year OS was 100% (10-year: 83%). The 5-year FFLP and FFDP were 88% (10-year: 44%) and 67% (10-year: 34%), respectively. In patients who received multi-modal treatment including surgery and adjuvant radiotherapy, the 5-year OS was 84% (10-year: 84%). The 5-year FFLP was 100% (10-year: 100%) and the 5-year FFDP was 65% (10-year, 65%).

Conclusions

The long-term prognosis is favorable if surgery is performed. In cases of an incomplete resection, good OS can still be achieved following adjuvant radiotherapy. For radiotherapy, irradiation with C¹² shows promising first results. However, more data is needed to prove the long-term advantage of C¹² over photons.

Trial registration

The ethics committee of the Heidelberg University Hospital approved the retrospective data analysis (S-174/2019).

Radiation oncology in the era of precision medicine

Technological advances and clinical research over the past few decades have given radiation oncologists the capability to personalize treatments for accurate delivery of radiation dose based on clinical parameters and anatomical information. Eradication of gross and microscopic tumours with preservation of health-related quality of life can be achieved in many patients. Two major strategies, acting synergistically, will enable further widening of the therapeutic window of radiation oncology in the era of precision medicine: technology-driven improvement of treatment conformity, including advanced image guidance and particle therapy, and novel biological concepts for personalized treatment, including biomarker-guided prescription, combined treatment modalities and adaptation of treatment during its course.

Radiation oncology: physics advances that minimize morbidity

ABSTRACT 

Radiation therapy has become an ever more successful treatment for many cancer patients. This is due in large part from advances in physics including the expanded use of imaging protocols combined with ever more precise therapy devices such as linear and particle beam accelerators, all contributing to treatments with far fewer side effects. This paper will review current state-of-the-art physics maneuvers that minimize morbidity, such as intensity-modulated radiation therapy, volummetric arc therapy, image-guided radiation, radiosurgery and particle beam treatment. We will also highlight future physics enhancements on the horizon such as MRI during treatment and intensity-modulated hadron therapy, all with the continued goal of improved clinical outcomes.

Immune modulation and stereotactic radiation: improving local and abscopal responses

New and innovative treatment strategies for cancer patients in the fields of immunotherapy and radiotherapy are rapidly developing in parallel. Among the most promising preclinical treatment approaches is combining immunotherapy with radiotherapy where early data suggest synergistic effects in several tumor model systems. These studies demonstrate that radiation combined with immunotherapy can result in superior efficacy for local tumor control. More alluring is the emergence of data suggesting an equally profound systemic response also known as "abscopal" effects with the combination of radiation and certain immunotherapies. Studies addressing optimal radiation dose, fractionation, and modality to be used in combination with immunotherapy still require further exploration. However, recent anecdotal clinical reports combining stereotactic or hypofractionated radiation regimens with immunotherapy have resulted in dramatic sustained clinical responses, both local and abscopal. Technologic advances in clinical radiation therapy has made it possible to deliver hypofractionated regimens anywhere in the body using stereotactic radiation techniques, facilitating further clinical investigations. Thus, stereotactic radiation in combination with immunotherapy agents represents an exciting and potentially fruitful new space for improving cancer therapeutic responses.

Future radiation therapy: photons, protons and particles

Radiation therapy plays a critical role in the current management of cancer patients. The most common linear accelerator-based treatment device delivers photons of radiation. In an ever more precise fashion, state-of-the-art technology has recently allowed for both modulation of the radiation beam and imaging for this treatment delivery. This has resulted in better patient outcome with far fewer side effects than were achieved even a decade ago. Recently, a push has begun for proton therapy, which may have clinical advantage in select indications, although significant limitations for these devices have become apparent. In addition, currently, heavy particle therapy has been touted as a potential means to improve cancer patient outcomes. This article will highlight current benefits and drawbacks to modern radiation therapy and speculate on future tools that will likely dramatically improve radiation oncology.