Proton Beam Therapy for Treating Patients with Hepatocellular Carcinoma with Major Portal Vein Tumor Invasion: A Single Center Retrospective Study.

Hepatocellular carcinoma (HCC) with portal vein tumor thrombosis (PVTT) has a poor prognosis and is generally not indicated for surgery. Proton beam therapy (PBT) may offer an alternative treatment. In this study, long-term outcomes were examined in 116 patients (median age 66 years, 100 males) with HCC with advanced PVTT (Vp3 or Vp4) who received PBT from April 2008 to March 2018. Of these patients, 63 received PBT as definitive treatment and 53 as palliative treatment. The representative dose was 72.6 Gy (RBE) in 22 fractions. Eight patients died in follow-up, including 72 due to tumor progression. The 5-year overall survival (OS) rate was 18.0% (95% CI 9.8-26.2%) and the 5-year local control (LC) rate was 86.1% (74.9-97.3%). In multivariate analyses, performance status and treatment strategy were significantly associated with OS. The median follow-up period for survivors with definitive treatment was 33.5 (2-129) months, and the 5-year OS rate was 25.1% (12.9-37.3%) in these cases. The median survival time after definitive irradiation was >20 months. The 5-year OS rate was 9.1% (0-19.7%) for palliative irradiation. These results compare favorably with those of other therapies and suggest that PBT is a useful option for cases of HCC with advanced PVTT that cannot undergo surgery, with an expected survival benefit and good local control. Determining the optimal indication for this treatment is a future challenge.

Moderately hypofractionated proton beam therapy for localized prostate cancer: 5-year outcomes of a phase II trial.

The usefulness of moderately hypofractionated radiotherapy for localized prostate cancer has been extensively reported, but there are limited studies on proton beam therapy (PBT) using similar hypofractionation schedules. The aim of this prospective phase II study is to confirm the safety of a shortened PBT course using 70 Gy relative biological effectiveness (RBE) in 28 fractions. From May 2013 to June 2015, 102 men with localized prostate cancer were enrolled. Androgen deprivation therapy was administered according to risk classification. Toxicity was assessed using Common Terminology Criteria for Adverse Events version 4.0. Of the 100 patients ultimately evaluated, 15 were classified as low risk, 43 as intermediate risk, and 42 as high risk. The median follow-up time of the surviving patients was 96 months (range: 60-119 months). The 5-year cumulative incidences of grade 2 gastrointestinal/genitourinary adverse events were 1% (95% CI: 0.1-6.9) and 4% (95% CI: 1.5-10.3), respectively; no grade ≥ 3 gastrointestinal/genitourinary adverse events were observed. The current study revealed a low incidence of late adverse events in prostate cancer patients treated with moderately hypofractionated PBT of 70 Gy (RBE) in 28 fractions, indicating the safety of this schedule.

Late Changes in Renal Volume and Function after Proton Beam Therapy in Pediatric and Adult Patients: Children Show Significant Renal Atrophy but Deterioration of Renal Function Is Minimal in the Long-Term in Both Groups.

To compare late renal effects in pediatric and adult patients with malignancies after PBT involving part of the kidney. A retrospective study was conducted to assess changes in renal volume and function in 24 patients, including 12 children (1-14 years old) and 12 adults (51-80 years old). Kidney volumes were measured from CT or MRI images during follow-up. Dose-volume histograms were calculated using a treatment planning system. In children, the median volume changes for the irradiated and control kidneys were -5.58 (-94.95 to +4.79) and +14.92 (-19.45 to +53.89) mL, respectively, with a relative volume change of -28.38 (-119.45 to -3.87) mL for the irradiated kidneys. For adults, these volume changes were -22.43 (-68.7 to -3.48) and -21.56 (-57.26 to -0.16) mL, respectively, with a relative volume change of -5.83 (-28.85 to +30.92) mL. Control kidneys in children exhibited a marked increase in size, while those in adults showed slight volumetric loss. The percentage of irradiated volume receiving 10 Gy (RBE) (V10) and 20 Gy (RBE) (V20) were significantly negatively associated with the relative volume change per year, especially in children. The CKD stage based on eGFR for all patients ranged from 1 to 3 and no cases with severe renal dysfunction were found before or after PBT. Late effects on the kidneys after PBT vary among age groups. Children are more susceptible than adults to significant renal atrophy after PBT. V10 and V20 might serve as predictors of the degree of renal atrophy after PBT, especially in children. PBT has a minimal impact on deterioration of renal function in both children and adults.

Multimodal treatment with chemoradiotherapy, regional hyperthermia and interstitial brachytherapy for a huge locally advanced cervical cancer: A case report.

A female patient in her 50 s was found to have a 10-cm tumor resulting from locally advanced cervical cancer (LACC). Three-year relapse-free survival was achieved following a multimodal treatment strategy integrating chemoradiotherapy (CRT), regional hyperthermia (RHT), and interstitial brachytherapy (ISBT). Given the large size of the tumor, enhancement of the geometrical dose distribution was anticipated using ISBT. However, delivery of a sufficient dose to the high-risk clinical target volume was predicted to be challenging. Thus, RHT was incorporated to potentially augment the overall treatment effect. This unique combination of CRT, RHT and ISBT may be promising for management of large LACC and warrants further investigation.

Proton beam therapy for hepatocellular carcinoma with bile duct invasion.

AIM: Hepatocellular carcinoma (HCC) with bile duct invasion (BDI) (BDIHCC) has a poor prognosis. Moreover, due to the paucity of reports, there is no consensus regarding optimal management of this clinical condition yet. The aim of this study was to clarify the efficacy and safety of proton beam therapy (PBT) for BDIHCC. METHODS: Between 2009 and 2018, 15 patients with BDIHCC underwent PBT at our institution. The overall survival (OS), local control (LC), and progression-free survival (PFS) curves were constructed using the Kaplan-Meier method. Toxicities were assessed using the Common Terminology Criteria of Adverse Events version 4.0. RESULTS: The median follow-up time was 23.4 months (range, 7.9-54.3). The median age was 71 years (range, 58-90 years). Many patients were Child A (n = 8, 53.3%) and most had solitary tumors (n = 11, 73.3%). Additionally, most patients had central type BDI (n = 11, 73%). The median tumor size was 4.0 cm (range, 1.5-8.0 cm). The 1-, 2-, and 3-year OS rates were 80.0%, 58.7% and 40.2%, respectively, and the corresponding LC and PFS rates were 93.3%, 93.3%, and 74.7% and 72.7%, 9.7%, and 0.0%, respectively. Acute grade 1/2 dermatitis (n = 7, 46.7%), and grades 2 (n = 1, 6.7%) and 3 (n = 1, 6.7%) cholangitis were observed. Late toxicities such as grade 3 gastric hemorrhage and pleural effusion were observed. No toxicities of grade 4 or higher were observed. CONCLUSIONS: PBT was feasible with tolerable toxicities for the treatment of BDIHCC.

Proton beam therapy in multimodal treatment for locally advanced squamous cell carcinoma of the nasal cavity and paranasal sinus.

BACKGROUND: To evaluate proton beam therapy (PBT) in multimodal treatment for locally advanced squamous cell carcinoma of the nasal cavity and paranasal sinus (NPSCC). METHODS: The cases in this study included T3 and T4 NPSCC without distant metastases that were treated at our center using PBT between July 2003 and December 2020. These cases were classified into 3 groups based on resectability and treatment strategy: surgery followed by postoperative PBT (group A); those indicated to be resectable, but the patient refused surgery and received radical PBT (group B); and those declared unresectable based on the extent of the tumor and treated with radical PBT (group C). RESULTS: The study included 37 cases, with 10, 9 and 18 in groups A, B and C, respectively. The median follow-up period in surviving patients was 4.4 years (range 1.0-12.3 years). The 4-year overall survival (OS), progression-free survival (PFS), and local control (LC) rates were 58%, 43% and 58% for all patients; 90%, 70% and 80% in group A, 89%, 78% and 89% in group B; and 24%, 11% and 24% in group C. There were significant differences in OS (p = 0.0028) and PFS (p = 0.009) between groups A and C; and in OS (p = 0.0027), PFS (p = 0.0045) and LC (p = 0.0075) between groups B and C. CONCLUSIONS: PBT gave favorable outcomes in multimodal treatment for resectable locally advanced NPSCC, including surgery followed by postoperative PBT and radical PBT with concurrent chemotherapy. The prognosis for unresectable NPSCC was extremely poor, and reconsideration of treatment strategies, such as more active use of induction chemotherapy, may improve outcomes.

Clinical Impact of Proton Beam Therapy for Postoperative Lymph Node Oligorecurrence of Esophageal Cancer.

BACKGROUND/AIM: Radiotherapy is a salvage therapy type for postoperative recurrence of esophageal cancer. Compared to conventional photon-based radiotherapy, proton beam therapy can reduce the irradiated dose to the surrounding organs, facilitating the management of patients who are unfit for radiotherapy. In this study, the outcomes and toxicity of proton beam therapy for postoperative lymph node oligorecurrence of esophageal cancer were investigated. PATIENTS AND METHODS: We retrospectively evaluated the clinical outcomes and toxicity of 13 sites in 11 patients treated with proton beam therapy for postoperative lymph node oligorecurrence of esophageal cancer. In total, eight men and three women with a median age of 68 years (range=46-83 years) were included. RESULTS: The median follow-up period was 20.2 months. During the follow-up period, four patients died of esophageal cancer. Eight of the 11 patients developed recurrence; of these, seven patients had recurrence outside the irradiated field, and one had recurrence inside and outside the irradiated field. The 2-year overall survival, progression-free survival, and local control rates were 48.0%, 27.3%, and 84.6%, respectively. The median survival time was 22.4 months. There were no severe acute or late adverse events. CONCLUSION: Proton beam therapy could be a safe and effective treatment method for postoperative lymph node oligorecurrence of esophageal cancer. It may be beneficial even in cases where conventional photon-based radiotherapy is difficult to administer in combination with increased doses or with chemotherapy.

Long-term Outcomes After Moderate Hypofractionated Proton Therapy for Centrally Located Non-small Cell Lung Cancer.

BACKGROUND/AIM: To investigate the outcomes of patients with centrally located non-small-cell lung cancer (NSCLC) treated with proton beam therapy (PBT) using moderate hypofractionation. PATIENTS AND METHODS: Between 2006 and 2019, 34 patients with centrally located T1-T4N0M0 NSCLC who received moderate hypofractionated PBT were retrospectively reviewed. RESULTS: The median follow-up was 50.8 months (range=5.8-100.4 months). The 3-year overall survival, progression-free survival (PFS), and local control rates were 70.4%, 55.5% and 80.5%, respectively. Grade 2 or 3 lung adverse events (AEs) after PBT were observed in five (14.7%) patients; however, grade 3 radiation pneumonitis was observed in one (2.9%) patient. Notably, no grade 4 or higher AEs were observed. Regarding the correlation between the lung dose and proximal bronchial tree maximum dose and grade 2 or higher lung AEs, a weak correlation was observed between the mean lung dose and AEs (p=0.035). Although the clinical target volume (CTV) was a risk factor for poor PFS, no significant correlation was found between the CTV and lung AEs after PBT. CONCLUSION: Moderate hypofractionated PBT may be a useful radiotherapy method for centrally located cT1-T4N0M0 NSCLC.

Light flash and odor during proton beam therapy for pediatric patients: a prospective observational study.

Light flash and odor during radiation therapy are well-known phenomena, but the details are poorly understood, particularly in pediatric patients. Therefore, we conducted a prospective observational study of these events in pediatric patients (age ≤20 years old) who received radiotherapy at our center from January 2019 to November 2021. Light flash and odor were evaluated using a patient-reported checklist including the presence, strength, and duration of the phenomenon, and color of light or type of odor. 53 patients who received proton therapy (n=47) and photon radiotherapy (n=6) were enrolled in this study. The median age of the patients was 10, ranged from 5 to 20. The patients who was able to see the light flash was 4, and all of them received retina irradiation. This was equivalent to 57% of the patients who received radiotherapy to retina (n=7). The light was bright and colored mainly blue and purple, which seemed to be consistent with Cherenkov light. Odor was sensed by 9 (17%) patients, and seven patients of the 9 received nasal cavity irradiation. This was equivalent to 41% of the patients who received nasal cavity irradiation (n=17). Other 2 patients received proton therapy to brain tumor. The odors were mainly described as plastic, burnt and disinfectant, which may be caused by ozone generated during irradiation. These data suggest that pediatric patients with retinal and nasal cavity irradiation frequently sense light flashes or odor. So adequate care is necessary so that these patients are not worried about this phenomenon.

Proton Beam Therapy in Elderly Patients With cT1-3N0M0 Non-small Cell Lung Cancer.

BACKGROUND/AIM: To investigate the outcomes of elderly patients with cT1-3N0M0 non-small cell lung cancer (NSCLC) undergoing proton beam therapy (PBT). PATIENTS AND METHODS: Between 2009 and 2019, 110 patients receiving hypofractionated PBT for cT1-3N0M0 NSCLC were retrospectively reviewed. RESULTS: The median follow-up was 36.5 months (range=4.9-131.0 months). In the elderly group (80 years or older), the 3-year overall survival and progression-free survival rates were 79.8% and 73.9%, respectively, and the corresponding rates in the younger group were 80.5% and 61.2%, respectively. Grade 3 radiation pneumonitis (RP) was observed in 4.4% patients in the young group, whereas no grade 3 RP was observed in the elderly group. Age was not a risk factor for symptomatic RP. There were no significant differences in the survival and adverse events between the elderly and younger groups. CONCLUSION: PBT may be a reasonable approach for treating lung cancer in elderly patients with T1-3N0M0 NSCLC.

A Case Report of Radiotherapy for Skull Lesions of Langerhans Cell Histiocytosis With Dural Invasion.

Background: Langerhans cell histiocytosis (LCH) is a rare disease, especially in adults. It is often associated with non-fatal bone and skin lesions and has relatively good radiosensitivity. In contrast, brain and lymph node metastases from LCH lesions are considered to be less sensitive to radiotherapy. Case Report: At our institution, 30 Gy radiotherapy was used to treat bone lesions with dural invasion in a patient with adult-onset LCH. The patient was treated with chemotherapy and radiotherapy for 21 years since the initial diagnosis. After radiotherapy, the tumor shrank rapidly, and a complete response was achieved 1 year after treatment. The patient survived without local recurrence. Conclusion: Here, we report the details of this case, along with a review of the literature. We suggest that even with invasion of the tissues around the bone lesions in LCH, local recurrence can be prevented by middle radiation doses.

Olfactory Sensations During Proton and Photon Radiotherapy: A Multicenter Prospective Observational Study.

PURPOSE: Patients often report a sense of smell during radiation therapy (RT), but the details of these events are not well understood. The purpose of the study was to evaluate events of smell during photon RT and proton beam therapy (PBT). METHODS AND MATERIALS: The subjects were all adult patients (≥20 years old) treated with photon RT or PBT at two centers from January 2019 to August 2020, with the exclusion of those with communication difficulties or olfactory abnormality. The presence of smell, odor type, intensity (five levels), and time period was examined prospectively using a weekly checklist. RESULTS: A total of 649 courses were examined in 620 patients who received photon RT (n=415) or PBT (n=205). A smell during the procedure was sensed by 51 patients (8.2%). In multivariate logistic regression analysis, nasal cavity dose (p=0.002), age (p<0.001), and photon RT (p=0.018) were identified as significant factors associated with a sense of smell. Smell occurred in only 23/515 patients (4.5%) in whom the nasal cavity was not irradiated, but in 4/19 (21.1%) and 24/86 (27.9%) with nasal cavity maximum isodose lines of 10%-50% and 60%-100%, respectively. Patients who received photon RT sensed a smell (43/415; 10.4%) more frequently than those treated with PBT (8/205; 3.9%). Of the 51 patients who sensed a smell, 32 (63%) reported a burnt smell, eight (16%) a chemical smell, two (4%) a sour smell, and nine another smell (copier machine, sweet, garbage, etc.). CONCLUSIONS: The sense of a smell appears to be common during RT and this sensation is significantly associated with the nasal cavity dose, younger age, and photon RT.

Light flashes during proton and photon radiotherapy: A multicenter prospective observational study.

BACKGROUND: Patients who receive radiation therapy sometimes complain of a light flash during irradiation. The details of the characteristics of this light have not been described. PURPOSE: To evaluate light flashes during photon and proton radiotherapy. METHODS AND MATERIALS: A prospective observational study was performed in all adult patients (≥20 years old) who received photon and proton therapy at two centers between January 2019 and August 2020, except for patients who could not communicate and those with visual abnormality. Evaluations were obtained for the presence or absence of light flashes, light darkness (7 levels), light intensity (5 levels), frequency, light movement, light flashing, and time seeing the light, using a weekly checklist. RESULTS: A total of 650 courses were examined for 621 patients, of whom 416 received photon radiotherapy and 205 received proton beam therapy. The checklist indicated that 88 patients (16.1%) sensed light during photon or proton radiotherapy. In multivariate logistic regression analysis, the factors that were significantly associated with a light flash were a higher retina dose and younger age (p < 0.001). Light flashes were seen by only 35/524 patients (6.7%) for whom the retina was not irradiated, but by 13/33 (39.4%) and 41/64 (64.1%) with maximum isodose lines for the retina of 10-50% and 60-100%, respectively. The numbers of patients who sensed blue, purple, yellow, red, white and other colors were 52, 15, 15, 9, 16 and 8, respectively (multiple selections possible). Light movement was observed by 52 patients (59%). The location of the light was defined as near, far, and middle by 70, 13, and 5 patients, respectively. The median time the light was seen was 10 s. CONCLUSIONS: Many patients sense light flashes during radiotherapy. The retina dose and a younger age were significantly associated with the frequency of light flashes.

The impact of lymphopenia during chemoradiotherapy using photons or protons on the clinical outcomes of esophageal cancer patients.

We assessed the development of lymphopenia during concurrent chemoradiotherapy (CRT) using X-ray versus proton beams and the impact on survival in patients with esophageal cancer. Among patients with esophageal cancer who were administered concurrent CRT with a curative intent at our institute from 2014 to 2018, 69 (15 receiving X-ray radiotherapy (XRT) and 54 receiving proton beam therapy [PBT]) who underwent weekly blood testing during treatment were enrolled. The absolute lymphocyte counts (ALC) at 1, 5 and 6 weeks were significantly higher in the patients who received PBT than in those who received XRT (p = 0.002, p = 0.006 and p = 0.009, respectively), and a similar trend in the neutrophil-to-lymphocyte ratio (NLR) was observed (p = 0.003 at 5 weeks). The 2-year overall survival (OS) and progression-free survival (PFS) rates tended to be higher in the patients who maintained an ALC ≥200 compared with those who did not (p = 0.083 and p = 0.053, respectively), and similar trends were observed in the NLR (p = 0.061 and p = 0.038, respectively). Dose-volume analysis revealed significant correlations between volumes of the thoracic bones irradiated by 5-50 Gy and minimum ALCs and maximum NLR. These findings suggested that PBT prevented the development of lymphopenia during CRT by reducing the irradiated volume of the thoracic bone, and the maintained lymphocyte count is possibly one of the early predictors for survival in patients with esophageal cancer.

Proton Beam Therapy for Local Recurrence of Rectal Cancer.

BACKGROUND/AIM: Curing local recurrence of rectal cancer (LRRC) is difficult with conventional photon radiotherapy. Proton beam therapy (PBT) on the other hand, has unique physical characteristics that permit higher doses to LRRC while minimizing side effects on surrounding organs. However, the efficacy of PBT on controlling rectal cancer recurrence has not yet been reported. This study aimed to evaluate clinical outcomes and toxicities of PBT for LRRC. PATIENTS AND METHODS: Clinical outcomes were retrospectively evaluated for 12 patients with 13 total lesions that had received PBT for LRRC at our institute. RESULTS: The median follow-up period from the initiation of PBT was 35.6 months. The 3-year local control, progression-free survival and overall survival rates were 80.2%, 10.4% and 73.8%, respectively. Median survival time was 67.1 months. There were no severe acute or late adverse events. CONCLUSION: PBT could be a safe and effective treatment method for LRRC.

Proton beam therapy for a giant hepatic hemangioma: A case report and literature review.

BACKGROUND: Hepatic hemangiomas are benign tumors with a favorable prognosis, but giant hepatic hemangiomas can cause abdominal symptoms and are indicated for treatment. Most cases are treated with surgery, but radiotherapy has also been used. However, to date, there have been no reports of proton beam therapy for a hepatic hemangioma. CASE PRESENTATION: A 46-year-old woman had a tumor of 80 × 80 mm in the left medial lobe of the liver, which was diagnosed as a giant hemangioma based on the contrast pattern. Therapy was required for a giant hepatic hemangioma with symptoms, but the patient refused blood transfusion due to religious reasons, which made surgical resection difficult. Therefore, she was referred to our hospital for proton beam therapy. At her first visit, liver function was Child-Pugh A (5 points) and there was no elevation of tumor markers. Proton beam therapy of 28.6 Gy (RBE) given in 13 fractions was performed without interruption. The only observed acute radiation toxicity was Grade 1 dermatitis. One year after proton beam therapy, the hemangioma had significantly decreased, and a complete response has been maintained for 15 years based on ultrasound and MRI. CONCLUSION: This case is the first reported use of proton beam therapy for a hepatic hemangioma. The outcome suggests that this treatment may be effective for a giant liver hemangioma.

Optimal Androgen Deprivation Therapy Combined with Proton Beam Therapy for Prostate Cancer: Results from a Multi-Institutional Study of the Japanese Radiation Oncology Study Group.

BACKGROUND: Androgen deprivation therapy (ADT) combined with radiation therapy benefits intermediate- and high-risk prostate cancer (PC) patients. The optimal ADT duration in combination with high-dose proton beam therapy (PBT) remains unknown. METHODS: Intermediate- and high-risk PC patients treated with PBT combined with ADT for various durations were analyzed retrospectively. To assess the relationship between ADT and biochemical relapse-free (bRF) rate, Cox proportional hazards models including T stage, prostate specific antigen (PSA) level, Gleason score (GS), and total radiation dose were used. RESULTS: In the intermediate-risk PC patients (n = 520), ADT use improved bRF (HR 0.49, 95% CI 0.26-0.93; p = 0.029), especially in those with multiple intermediate-risk factors (T2b-2c, PSA 10-20 ng/mL, and GS 7). In the high-risk PC patients (n = 555), a longer ADT duration (>6 months) conferred a benefit for bRF (HR 0.54, 95% CI 0.32-0.90; p = 0.018), which was most apparent in patients with multiple high-risk factors (T3a-4, PSA > 20 ng/mL, and GS ≥ 8) treated with ADT for ≥21 months. CONCLUSIONS: Short-term (≤6 months) ADT is beneficial for intermediate-risk PC patients, but likely unnecessary for those with a single risk factor, whereas ADT for >6 months is necessary for high-risk PC patients and ADT for ≥21 months might be optimal for those with multiple risk factors in combination of high-dose PBT.

Transitions of Liver and Biliary Enzymes during Proton Beam Therapy for Hepatocellular Carcinoma.

Proton beam therapy (PBT) is a curative treatment for hepatocellular carcinoma (HCC), because it can preserve liver function due to dose targeting via the Bragg peak. However, the degree of direct liver damage by PBT is unclear. In this study, we retrospectively analyzed liver/biliary enzymes and total bilirubin (T-Bil) as markers of direct liver damage during and early after PBT in 300 patients. The levels of these enzymes and bilirubin were almost stable throughout the treatment period. In patients with normal pretreatment levels, aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT), and T-Bil were abnormally elevated in only 2 (1.2%), 1 (0.4%), 0, 2 (1.2%), and 8 (3.5%) patients, respectively, and in 8 of these 13 patients (61.5%) the elevations were temporary. In patients with abnormal pretreatment levels, the levels tended to decrease during PBT. GGT and T-Bil were elevated by 1.62 and 1.57 times in patients who received 66 Gy (RBE) in 10 fractions and 74 Gy (RBE) in 37 fractions, respectively, but again these changes were temporary. These results suggest that direct damage to normal liver caused by PBT is minimal, even if a patient has abnormal pretreatment enzyme levels.

Three cases of hepatocellular carcinoma treated 4 times with proton beams.

HCC may recur following surgery or radiofrequency ablation. Proton beam therapy (PBT) is a type of radiotherapy that achieves excellent local control of HCC without severe toxicity. The present study reported the long-term outcome of 3 HCC patients who each received 4 repeat courses of PBT. All patients had a hepatitis B or C viral infection. A total of 14 lesions were treated using a curative PBT protocol and irradiated liver volumes in each treatment were 7-50% of the total liver volume. Liver function in all cases was considerably preserved until the last follow-up and patient survival was 51-107 months from the first PBT with no local recurrence observed in the 14 lesions. The presented cases indicated that repeated PBT is an effective treatment option for recurrent HCC due to reduced liver damage and superior local treatment compared with other treatment options such as transarterial chemoembolization.

Particle therapy for prostate cancer: The past, present and future.

Although prostate cancer control using radiotherapy is dose-dependent, dose-volume effects on late toxicities in organs at risk, such as the rectum and bladder, have been observed. Both protons and carbon ions offer advantageous physical properties for radiotherapy, and create favorable dose distributions using fewer portals compared with photon-based radiotherapy. Thus, particle beam therapy using protons and carbon ions theoretically seems suitable for dose escalation and reduced risk of toxicity. However, it is difficult to evaluate the superiority of particle beam radiotherapy over photon beam radiotherapy for prostate cancer, as no clinical trials have directly compared the outcomes between the two types of therapy due to the limited number of facilities using particle beam therapy. The Japanese Society for Radiation Oncology organized a joint effort among research groups to establish standardized treatment policies and indications for particle beam therapy according to disease, and multicenter prospective studies have been planned for several common cancers. Clinical trials of proton beam therapy for intermediate-risk prostate cancer and carbon-ion therapy for high-risk prostate cancer have already begun. As particle beam therapy for prostate cancer is covered by the Japanese national health insurance system as of April 2018, and the number of facilities practicing particle beam therapy has increased recently, the number of prostate cancer patients treated with particle beam therapy in Japan is expected to increase drastically. Here, we review the results from studies of particle beam therapy for prostate cancer and discuss future developments in this field.