The clinical experience with particle therapy in adults

Therapeutic Sequences in the Treatment of High-Risk Prostate Cancer: Paving the Way Towards Multimodal Tailored Approaches

Various definitions are currently in use to describe high-risk prostate cancer. This variety in definitions is important for patient counseling, since predicted outcomes depend on which classification is applied to identify patient’s prostate cancer risk category. Historically, strategies for the treatment of localized high-risk prostate cancer comprise local approaches such as surgery and radiotherapy, as well as systemic approaches such as hormonal therapy. Nevertheless, since high-risk prostate cancer patients remain the group with higher-risk of treatment failure and mortality rates, nowadays, novel treatment strategies, comprising hypofractionated-radiotherapy, second-generation antiandrogens, and hadrontherapy, are being explored in order to improve their long-term oncological outcomes. This narrative review aims to report the current management of high-risk prostate cancer and to explore the future perspectives in this clinical setting.

Proton therapy- the modality of choice for future radiation therapy management of Prostate Cancer?

BACKGROUND

Proton Therapy (PR) is an emerging treatment for prostate cancer (Pca) patients. However, limited and conflicting data exists regarding its ability to result in fewer bladder and rectal toxicities compared to Photon Therapy (PT), as well as its cost efficiency and plan robustness.

MATERIALS AND METHODS

An electronic literature search was performed to acquire eligible studies published between 2007 and 2018. Studies comparing bladder and rectal dosimetry or Gastrointestinal (GI) and Genitourinary (GU) toxicities between PR and PT, the plan robustness of PR relative to motion and its cost efficiency for Pca patients were assessed.

RESULTS

28 studies were eligible for inclusion in this review. PR resulted in improved bladder and rectal dosimetry but did not manifest as improved GI/GU toxicities clinically compared to PT. PR plans were considered robust when specific corrections, techniques, positioning or immobilisation devices were applied. PR is not cost effective for intermediate risk Pca patients; however PR may be cost effective for younger or high risk Pca patients.

CONCLUSION

PR offers improved bladder and rectal dosimetry compared to PT but this does not specifically translate to improved GI/GU toxicities clinically. The robustness of PR plans is acceptable under specific conditions. PR is not cost effective for all Pca patients.

Clinical trials involving carbon-ion radiation therapy and the path forward

To describe the international landscape of clinical trials in carbon-ion radiotherapy (CIRT), the authors reviewed the current status of 63 ongoing clinical trials (median, 47 participants) involving CIRT identified from the US clinicaltrials.gov trial registry and the World Health Organization International Clinical Trials Platform Registry. The objectives were to evaluate the potential for these trials to define the role of this modality in the treatment of specific cancer types and identify the major challenges and opportunities to advance this technology. A significant body of literature suggested the potential for advantageous dose distributions and, in preclinical biologic studies, the enhanced effectiveness for CIRT compared with photons and protons. In addition, clinical evidence from phase I/II trials, although limited, indicated the potential for CIRT to improve cancer outcomes. However, current high-level phase III randomized clinical trial evidence does not exist. Although there has been an increase in the number of trials investigating CIRT since 2010, and the number of countries and sites offering CIRT is slowly growing, this progress has excluded other countries. Several recommendations are proposed to study this modality to accelerate progress in the field, including: 1) increasing the number of multinational randomized clinical trials, 2) leveraging the existing CIRT facilities to launch larger multinational trials directed at common cancers combined with high-level quality assurance; and 3) developing more compact and less expensive next-generation treatment systems integrated with radiobiologic research and preclinical testing.

The efficacy of human placenta-derived mesenchymal stem cells on radiation enteropathy along with proteomic biomarkers predicting a favorable response

BACKGROUND

Radiation enteropathy is a common complication in patients with abdominopelvic cancer, but no treatment has yet been established. Stem cell therapy may be a viable therapeutic option because intestinal stem cells are highly vulnerable to ionizing radiation (IR) and stem cell loss explains its intractability to general treatment. Here, we investigated either prophylactic or therapeutic efficacy of human placenta-derived mesenchymal stem cells (hPDSCs) against radiation enteropathy and could identify biomarkers predicting a favorable response to stem cell therapy.

METHODS

We challenged a radiation-induced enteropathy model with hPDSCs. After sacrifice, we checked the gross anatomy of small intestine, histology gross, and analyzed that, accompanied with molecular changes implicated in this model.

RESULTS

hPDSCs significantly improved the outcome of mice induced with either radiation enteropathy or lethal radiation syndrome (P < 0.01). hPDSCs exerted inhibitory actions on inflammatory cytokines, the re-establishment of epithelium homeostasis was completed with increasing endogenous restorative processes as assessed with increased levels of proliferative markers in the hPDSCs group, and a significant inhibition of IR-induced apoptosis. The preservation of cells expressing lysozyme, and Musashi-1 were significantly increased in the hPDSC treatment group. Both preventive and therapeutic efficacies of hPDSCs were noted against IR-induced enteropathy. Label-free quantification was used to identify biomarkers which predict favorable responses after hPDSC treatment, and finally glutathione S-transferase-mu type, interleukin-10, and peroxiredoxin-2 were validated as proteomic biomarkers predicting a favorable response to hPDSCs in radiation enteropathy.

CONCLUSIONS

hPDSCs may be a useful prophylactic and therapeutic cell therapy for radiation enteropathy.

Autophagy prevents irradiation injury and maintains stemness through decreasing ROS generation in mesenchymal stem cells

Stem cells were characterized by their stemness: self-renewal and pluripotency. Mesenchymal stem cells (MSCs) are a unique type of adult stem cells that have been proven to be involved in tissue repair, immunoloregulation and tumorigenesis. Irradiation is a well-known factor that leads to functional obstacle in stem cells. However, the mechanism of stemness maintenance in human MSCs exposed to irradiation remains unknown. We demonstrated that irradiation could induce reactive oxygen species (ROS) accumulation that resulted in DNA damage and stemness injury in MSCs. Autophagy induced by starvation or rapamycin can reduce ROS accumulation-associated DNA damage and maintain stemness in MSCs. Further, inhibition of autophagy leads to augment of ROS accumulation and DNA damage, which results in the loss of stemness in MSCs. Our results indicate that autophagy may have an important role in protecting stemness of MSCs from irradiation injury.

Phase I study evaluating the treatment of patients with locally advanced pancreatic cancer with carbon ion radiotherapy: the PHOENIX-01 trial

Background

Treatment options for patients with locally advanced pancreatic cancer include surgery, chemotherapy as well as radiotherapy. In many cases, surgical resection is not possible, and therefore treatment alternatives have to be performed. Chemoradiation has been established as a convincing treatment alternative for locally advanced pancreatic cancer. Carbon ions offer physical and biological characteristics. Due to their inverted dose profile and the high local dose deposition within the Bragg peak precise dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increased relative biological effectiveness (RBE), which can be calculated between 1.16 and 2.46 depending on the pancreatic cancer cell line as well as the endpoint analyzed. Japanese Data on the evaluation of carbon ion radiation therapy showed promising results for patients with pancreatic cancer.

Methods and design

The present PHOENIX-01 trial evaluates carbon ion radiotherapy using the active rasterscanning technique in patients with advanced pancreatic cancer in combination with weekly gemcitabine and adjuvant gemcitabine. Primary endpoint is toxicity, secondary endpoints are overall survival, progression-free survival and response.

Discussion

The physical and biological properties of the carbon ion beam promise to improve the therapeutic ratio in patients with pancreatic cancer: Due to the inverted dose profile dose deposition in the entry channel of the beam leads to sparing of normal tissue; the Bragg peak can be directed into the defined target volume, and the sharp dose fall-off thereafter again spares normal tissue behind the target volume. The higher RBE of carbon ions, which has been shown also for pancreatic cancer cell lines in the preclinical setting, is likely to contribute to an increase in local control, and perhaps in OS. Early data from Japanese centers have shown promising results. In conclusion, this is the first trial to evaluate actively delivered carbon ion beams in patients with locally advanced pancreatic cancer within a dose-escalation strategy.

Trial registration

NCT01795274

Chromosomal aberrations in the bone marrow cells of mice induced by accelerated (12)C(6+) ions

The whole bodies of 6-week-old male Kun-Ming mice were exposed to different doses of (12)C(6+) ions or X-rays. Chromosomal aberrations of the bone marrow (gaps, terminal deletions and breaks, fragments, inter-chromosomal fusions and sister-chromatid union) were scored in metaphase 9h after exposure, corresponding to cells exposed in the G(2)-phase of the first mitosis cycle. Dose-response relationships for the frequency of chromosomal aberrations were plotted both by linear and linear-quadratic equations. The data showed that there was a dose-related increase in the frequency of chromosomal aberrations in all treated groups compared to controls. Linear-quadratic equations were a good fit for both radiation types. The compound theory of dual radiation action was applied to decipher the bigger curvature (D(2)) of the dose-response curves of X-rays compared to those of (12)C(6+) ions. Different distributions of the five types of aberrations and different degrees of homogeneity were found between (12)C(6+) ion and X-ray irradiation and the possible underlying mechanism for these phenomena were analyzed according to the differences in the spatial energy deposition of both types of radiation.

Chromosome aberration measurements in mitotic and G2-PCC lymphocytes at the standard sampling time of 48 h underestimate the effectiveness of high-LET particles

The relationship between heavy-ion-induced cell cycle delay and the time-course of aberrations in first-cycle metaphases or prematurely condensed G(2)-cells (G(2)-PCC) was investigated. Lymphocytes of the same donor were irradiated with X-rays or various charged particles (carbon, iron, xenon, and chromium) covering an LET range of 2-3,160 keV/μm. Chromosome aberrations were measured in samples collected at 48, 60, 72, and 84 h postirradiation. Linear-quadratic functions were fitted to the data, and the fit parameters α and β were determined. At any sampling time, α values derived from G(2)-cells were higher than those from metaphases. The α value derived from metaphase analysis at 48 h increased with LET, reached a maximum around 155 keV/μm, and decreased with a further rise in LET. At the later time-points, higher α values were estimated for particles with LET > 30 keV/μm. Estimates of α values from G(2)-cells showed a similar LET dependence, yet the time-dependent increase was less pronounced. Altogether, our data demonstrate that heavily damaged lymphocytes suffer a prolonged G(2)-arrest that is clearly LET dependent. For this very reason, the standard analysis of aberrations in metaphase cells 48 h postirradiation will considerably underestimate the effectiveness of high-LET radiation. Scoring of aberrations in G(2)-PCC at 48 h as suggested by several authors will result in higher aberration yields. However, when particles with a very high-LET value (LET > 150 keV/μm) are applied, still a fraction of multiple damaged cells escape detection by G(2)-analysis 48 h postirradiation.

The potential benefit of radiotherapy with protons in head and neck cancer with respect to normal tissue sparing: a systematic review of literature

PURPOSE

Clinical studies concerning head and neck cancer patients treated with protons reporting on radiation-induced side effects are scarce. Therefore, we reviewed the literature regarding the potential benefits of protons compared with the currently used photons in terms of lower doses to normal tissue and the potential for fewer subsequent radiation-induced side effects, with the main focus on in silico planning comparative (ISPC) studies.

MATERIALS AND METHODS

A literature search was performed by two independent researchers on ISPC studies that included proton-based and photon-based irradiation techniques.

RESULTS

Initially, 877 papers were retrieved and 14 relevant and eligible ISPC studies were identified and included in this review. Four studies included paranasal sinus cancer cases, three included nasopharyngeal cancer cases, and seven included oropharyngeal, hypopharyngeal, and/or laryngeal cancer cases. Seven studies compared the most sophisticated photon and proton techniques: intensity-modulated photon therapy versus intensity-modulated proton therapy (IMPT). Four studies compared different proton techniques. All studies showed that protons had a lower normal tissue dose, while keeping similar or better target coverage. Two studies found that these lower doses theoretically translated into a significantly lower incidence of salivary dysfunction.

CONCLUSION

The results of ISPC studies indicate that protons have the potential for a significantly lower normal tissue dose, while keeping similar or better target coverage. Scanned IMPT probably offers the most advantage and will allow for a substantially lower probability of radiation-induced side effects. The results of these ISPC studies should be confirmed in properly designed clinical trials.

ENLIGHT and other EU-funded projects in hadron therapy

Following impressive results from early phase trials in Japan and Germany, there is a current expansion in European hadron therapy. This article summarises present European Union-funded projects for research and co-ordination of hadron therapy across Europe. Our primary focus will be on the research questions associated with carbon ion treatment of cancer, but these considerations are also applicable to treatments using proton beams and other light ions. The challenges inherent in this new form of radiotherapy require maximum interdisciplinary co-ordination. On the basis of its successful track record in particle and accelerator physics, the internationally funded CERN laboratories (otherwise known as the European Organisation for Nuclear Research) have been instrumental in promoting collaborations for research purposes in this area of radiation oncology. There will soon be increased opportunities for referral of patients across Europe for hadron therapy. Oncologists should be aware of these developments, which confer enhanced prospects for better cancer cure rates as well as improved quality of life in many cancer patients.

Relative biological effectiveness of carbon ions for local tumor control of a radioresistant prostate carcinoma in the rat

PURPOSE

To study the relative biological effectiveness (RBE) of carbon ion beams relative to X-rays for local tumor control in a syngeneic rat prostate tumor (Dunning subline R3327-AT1).

METHODS AND MATERIALS

A total of 198 animals with tumors in the distal thigh were treated with increasing single and split doses of either (12)C ions or photons using a 20-mm spread-out Bragg peak. Endpoints of the study were local control (no tumor recurrence within 300 days) and volumetric changes after irradiation. The resulting values for D(50) (dose at 50% tumor control probability) were used to determine RBE values.

RESULTS

The D(50) values for single doses were 32.9 ± 0.9 Gy for (12)C ions and 75.7 ± 1.6 Gy for photons. The respective values for split doses were 38.0 ± 2.3 Gy and 90.6 ± 2.3 Gy. The corresponding RBE values were 2.30 ± 0.08 for single and 2.38 ± 0.16 for split doses. The most prominent side effects were dry and moist desquamation of the skin, which disappeared within weeks.

CONCLUSION

The study confirmed the effectiveness of carbon ion therapy for severely radioresistant tumors. For 1- and 2-fraction photon and (12)C ion radiation, we have established individual D(50) values for local tumor control as well as related RBE values.