Comprehensive radiotherapy for pediatric Ewing Sarcoma: Outcomes of a prospective proton study

BACKGROUND AND PURPOSE

Patients with Ewing Sarcoma (EWS) are treated with multimodality therapy which includes radiation therapy (RT) as an option for local control. We report on the efficacy after proton radiation therapy (PRT) to the primary site for localized and metastatic EWS.

MATERIALS AND METHODS

Forty-two children with EWS (33 localized, 9 metastatic) treated between 2007 and 2020 were enrolled on 2 prospective registry protocols for pediatric patients undergoing PRT. PRT was delivered by passive scatter (74 %), pencil-beam scanning (12 %) or mixed technique (14 %). Treated sites included the spine (45 %), pelvis/sacrum (26 %), skull/cranium (14 %), extraosseous (10 %), and chest wall (5 %). Median radiation dose was 54 Gy-RBE (range 39.6-55.8 Gy-RBE). Patients with metastatic disease received consolidative RT to metastatic sites (4 at the time of PRT to the primary site, 5 after completion of chemotherapy). Median follow-up time was 47 months after PRT.

RESULTS

The 4-year local control (LC), progression-free survival (PFS), and overall survival (OS) rates were 83 %, 71 %, and 86 %, respectively. All local failures (n = 6) were in-field failures. Tumor size ≥ 8 cm predicted for inferior 4-year LC (69 % vs 95 %, p = 0.04). 4-year PFS and OS rates were not statistically different in patients with localized versus metastatic disease (72 % vs 67 %, p = 0.70; 89 % vs 78 %, p = 0.38, respectively).

CONCLUSION

In conclusion, LC for pediatric patients with EWS treated with PRT was comparable to that of historical patients who received photon-RT. Tumor size ≥ 8 cm predicted increased risk of local failure. Patients with metastatic disease, including non-pulmonary only metastases, received radiation therapy to all metastatic sites and had favorable survival outcomes.

The effectiveness and safety of proton beam radiation therapy in children and young adults with Central Nervous System (CNS) tumours: a systematic review

BACKGROUND

Central nervous system (CNS) tumours account for around 25% of childhood neoplasms. With multi-modal therapy, 5-year survival is at around 75% in the UK. Conventional photon radiotherapy has made significant contributions to survival, but can be associated with long-term side effects. Proton beam radiotherapy (PBT) reduces the volume of irradiated tissue outside the tumour target volume which may potentially reduce toxicity. Our aim was to assess the effectiveness and safety of PBT and make recommendations for future research for this evolving treatment.

METHODS

A systematic review assessing the effects of PBT for treating CNS tumours in children/young adults was undertaken using methods recommended by Cochrane and reported using PRISMA guidelines. Any study design was included where clinical and toxicity outcomes were reported. Searches were to May 2021, with a narrative synthesis employed.

RESULTS

Thirty-one case series studies involving 1731 patients from 10 PBT centres were included. Eleven studies involved children with medulloblastoma / primitive neuroectodermal tumours (n = 712), five ependymoma (n = 398), four atypical teratoid/rhabdoid tumour (n = 72), six craniopharyngioma (n = 272), three low-grade gliomas (n = 233), one germ cell tumours (n = 22) and one pineoblastoma (n = 22). Clinical outcomes were the most frequently reported with overall survival values ranging from 100 to 28% depending on the tumour type. Endocrine outcomes were the most frequently reported toxicity outcomes with quality of life the least reported.

CONCLUSIONS

This review highlights areas of uncertainty in this research area. A well-defined, well-funded research agenda is needed to best maximise the potential of PBT.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO-CRD42016036802.

Side Effects of Proton Beam Radiotherapy Treatment on Iris Melanoma

PURPOSE

This study evaluated the functional outcome and ocular side effects of patients receiving proton beam radiotherapy (PBR) for the treatment of iris melanoma (IM).

DESIGN

This retrospective study analyzed prospectively collected data.

PARTICIPANTS

Patients with IM who underwent PBR as a primary treatment.

METHODS

Treatment was given in the form of whole PBR (wPBR: n = 51) or segmental PBR (sPBR: n = 98).

MAIN OUTCOME MEASURES

Visual acuity (VA) and side effects were divided into ocular surface disease (OSD), secondary glaucoma, or cataract development.

RESULTS

A total of 149 eyes of 149 patients with a mean age of 53.9 ± 16.0 years were included. Tumor recurrence developed in 3 patients (wPBR: 1/51; sPBR: 2/98). Ocular surface disease was observed in 78.4% of the wPBR group (40/51) and 25.5% of the sPBR group (25/98) (P < 0.001) after 0.7 ± 1.2 years and 1.1 ± 0.9 years, respectively. The main side effect was dry eye syndrome in both groups, but severe side effects such as limbal stem cell failure were found only in the wPBR group (4/51; 7.8%). Secondary glaucoma developed in 31.4% of the wPBR group (16/51) compared with 1.0% in the sPBR group (1/98; P < 0.001). Glaucoma control was generally achieved with eye drops, whereas surgery was necessary in 5 patients (wPBR: 4/51, 7.8%; sPBR: 1/98, 1%). Cataract surgery was performed in 47.9% of the wPBR group (23/48) and 19.8% of the sPBR group (19/96) (P < 0.001). Before treatment, VA was 0.14 ± 0.27 logarithm of the minimum angle of resolution (logMAR) in the wPBR group and 0.04 ± 0.19 logMAR in the sPBR group. A worsening was seen in the wPBR group (0.55 ± 0.16 logMAR; P < 0.001) 6 months after radiotherapy, which normalized after 12 months (0.15 ± 0.30 logMAR; P = 0.17). In the sPBR group, no such decrease in VA was observed (6 months: 0.03 ± 0.22 logMAR, P = 0.54; 12 months: 0.04 ± 0.21 logMAR, P = 0.98).

CONCLUSIONS

Our results demonstrate that PBR is a very successful treatment option for patients with IM, showing a high tumor control rate and relatively low complication profile. Tumor recurrence was a rare event, and secondary enucleation was not necessary in any patient. Side effects are commonly seen, but severe side effects such as limbal stem cell failure or secondary glaucoma mainly developed after wPBR. These results are important for clinical decision making and discussion with the patient regarding this form of radiotherapy.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Proton Beam Therapy versus Radiofrequency Ablation for Patients with Treatment-Naïve Single Hepatocellular Carcinoma: A Propensity Score Analysis

Introduction

Proton beam therapy (PBT) is known to be an effective locoregional treatment for hepatocellular carcinoma (HCC). However, few comparative studies in treatment-naïve cases have been reported. The aim of this study was to compare the survival outcomes of PBT with those of radiofrequency ablation (RFA) in patients with treatment-naïve solitary HCC.

Methods

Ninety-five consecutive patients with treatment-naïve HCC, a single nodule measuring ≤5 cm in diameter, and a Child-Pugh score of ≤8 who were treated with PBT at the University of Tsukuba Hospital between 2001 and 2013 were enrolled in the study. In addition, 836 patients with treatment-naïve HCC treated by RFA at the University of Tokyo Hospital during the same period were analyzed as controls. Recurrence-free survival (RFS) and overall survival (OS) were compared in 83 patient pairs after propensity score matching.

Results

The 1-year, 3-year, and 5-year RFS rates were 86.6%, 49.5%, and 35.5%, respectively, in the PBT group and 59.5%, 34.0%, and 20.9% in the RFA group (p = 0.058); the respective OS rates were 97.6%, 77.8%, and 57.1% in the PBT group and 95.1%, 81.7%, and 67.7% in the RFA group (p = 0.16). Regarding adverse effects, no grade 3 or higher adverse events were noted in the PBT; however, two grade 3 adverse events occurred within 30 days of RFA in the RFA group: one hemoperitoneum and one hemothorax.

Discussion

After propensity score matching, PBT showed no significant difference in RFS and OS compared to RFA. PBT can be an alternative for patients with solitary treatment-naïve HCC.

Outcomes of intraventricular 131-I-omburtamab and external beam radiotherapy in patients with recurrent medulloblastoma and ependymoma

PURPOSE

Intraventricular compartmental radioimmunotherapy (cRIT) with 131-I-omburtamab is a potential therapy for recurrent primary brain tumors that can seed the thecal space. These patients often previously received external beam radiotherapy (EBRT) to a portion or full craniospinal axis (CSI) as part of upfront therapy. Little is known regarding outcomes after re-irradiation as part of multimodality therapy including cRIT. This study evaluates predictors of response, patterns of failure, and radiologic events after cRIT.

METHODS

Patients with recurrent medulloblastoma or ependymoma who received 131-I-omburtamab on a prospective clinical trial were included. Extent of disease at cRIT initiation (no evidence of disease [NED] vs measurable disease [MD]) was assessed as associated with progression-free (PFS) and overall survival (OS) by Kaplan-Meier analysis.

RESULTS

All 27 patients (20 medulloblastoma, 7 ependymoma) had EBRT preceding cRIT: most (22, 81%) included CSI (median dose 2340 cGy, boost to 5400 cGy). Twelve (44%) also received EBRT at relapse as bridging to cRIT. There were no cases of radionecrosis. At cRIT initiation, 11 (55%) medulloblastoma and 3 (43%) ependymoma patients were NED, associated with improved PFS (p = 0.002) and OS (p = 0.048) in medulloblastoma. Most relapses were multifocal. With medium follow-up of 3.0 years (95% confidence interval, 1.8-7.4), 6 patients remain alive with NED.

CONCLUSION

For patients with medulloblastoma, remission at time of cRIT was associated with significantly improved survival outcomes. Relapses are often multifocal, particularly in the setting of measurable disease at cRIT initiation. EBRT is a promising tool to achieve NED status at cRIT initiation, with no cases of radiation necrosis.

Novel "T-Dimension" Therapies for Pediatric Optic Pathway Glioma: A Timely, Targeted, and Tailored Treatment Trend

INTRODUCTION

Novel targeted and tailored therapies can substantially improve the prognosis for optic pathway glioma (OPG), especially when implemented in a timely manner. However, their tremendous potential remains underestimated. Therefore, in this study, we provide an updated overview of the clinical trials, current trends, and future perspectives for OPG's novel therapeutic strategies.

METHODS

We completed an extensive literature review using the PubMed, MEDLINE, and ClinicalTrials.gov databases. We analyzed and reported the data following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Thioguanine, procarbazine, lomustine, and vincristine/vinblastine, as well as cisplatin-etoposide, provided excellent results in advanced-phase trials. Selumetinib and trametinib, two oral MEK inhibitors, have been approved for recurrent or refractory OPGs in association with the angiogenetic inhibitor bevacizumab. Among the mTOR inhibitors, everolimus and sirolimus showed the best results. Stereotactic radiosurgery and proton beam radiation therapy have advantages over conventional radiotherapy regimens. Timely treatment is imperative for acute visual symptoms with evidence of tumor progression. This latest evidence can help define a novel "T-Dimension" for pediatric OPG therapies.

CONCLUSION

The novel "T-Dimension" for pediatric OPGs is based on recent evidence-based treatments, including combination chemotherapy regimens, molecular targeted therapies, stereotactic radiosurgery, and proton beam radiation therapy. Additional clinical trials are essential for validating each of these new therapies.

Hepatocellular adenoma initially diagnosed as hepatocellular carcinoma with resistance to proton beam radiotherapy - A case report

Introduction and importance

Hepatocellular adenoma (HCA) is a rare liver tumor. We report a case of a radio-resistant liver tumor that was removed surgically and found to be HCA.

Case presentation

A 37-year-old Japanese man was incidentally diagnosed with a liver tumor. He had no history of viral hepatitis nor metabolic disorders. MRI revealed a tumor enhancing in arterial phase, followed by washout in late phase, and hypointensity in hepatobiliary phase. A diagnosis of hepatocellular carcinoma (HCC) was made and surgery was advised. However, the patient chose proton beam radiotherapy. Although the tumor initially shrunk, it increased in size thereafter. Therefore, anterior sectionectomy was performed. Histology revealed proliferation of hepatocytes without cytologic atypia. On immunohistochemistry, CRP, SAA, GS, L-FABP, and nuclear expression of β-catenin were positive. A final diagnosis of mixed inflammatory and β-catenin activated HCA was made.

Clinical discussion

HCA is associated with obesity. The present case was a slightly obese man without history of viral hepatitis. In such cases, HCA should be considered. In the present case, proton beam radiotherapy was performed for a diagnosis of HCC. However, the tumor was radio-resistant.

Conclusion

HCA shows an almost equal male to female ratio in the Asian population. Molecular classification is vital in the management of HCA. HCC and HCA are often difficult to differentiate; tumor biopsy is necessary for patients with atypical imaging findings and in younger patients without underlying liver disease. Since the effectiveness of radiation therapy on HCA has not been reported, surgery should be preferred.

•

HCA is more prevalent in women in the western countries, while equal gender distribution in Asian countries

•

Subgroups show different imaging findings. I-HCA, atoll sign; b-HCA, iso-hyperintensity in the hepatobiliary phase

•

In the present case, the tumor showed resistance to radiation

Local tumour control and radiation side effects for fractionated stereotactic photon beam radiotherapy compared to proton beam radiotherapy in uveal melanoma

PURPOSE

To compare the adverse side effects of fractionated stereotactic photon beam radiotherapy (fSRT) with proton beam radiotherapy (PBR) in patients with uveal melanoma (UM).

METHODS

A retrospective study investigating 306 UM patients treated with fSRT (N=153) by the Rotterdam Ocular Melanoma Study group (ROMS), The Netherlands, between 1999-2014 or with PBR (N=153) at the Royal Liverpool University Hospital and the Clatterbridge Cancer Centre, Bebington, United Kingdom, between 1993-2014. The tumours treated with fSRT were matched with tumours treated with PBR based on sex, left or right eye, TNM classification, posterior margin ≤ or > 3mm of the fovea and of the optic disc.

RESULTS

The five-year actuarial rates of tumour recurrence were 4.5% for fSRT and 6.1% for PBR. For fSRT and PBR, the five-year actuarial rates of maculopathy were 14.9% and 12.4%, and for vitreous haemorrhage were 29.4% and 4.7%, respectively. Only vitreous haemorrhage (HR: 0.19, 95% CI: 0.07-0.56) was more common after fSRT compared to PBR. Overall, larger tumours were risk factors for maculopathy and secondary enucleation.

CONCLUSIONS

Both treatments have excellent local tumour control. In matched groups, vitreous haemorrhage was the only adverse side effect showing a significant difference between groups.

Is Proton Beam Radiotherapy Worthwhile in the Management of Angiosarcoma of the Scalp?

In inoperable patients, the management of angiosarcoma of the scalp is challenging. Due to intrinsic, dosimetric and radiobiological properties, proton beam radiotherapy may be an effective and safe option to offer to these difficult-to-cure patients. Here, we report a case of angiosarcoma of the scalp treated successfully with proton beam radiotherapy. Angiosarcoma is a rare malignancy concerning around 2% of soft-tissue sarcomas and 5% of cutaneous soft-tissue sarcomas. Cutaneous angiosarcomas can occur in any part of the body, but the head and neck region is a common primary site and the scalp is a frequent site in elderly patients.

Breakdown of the blood-eye barrier in choroidal melanoma after proton beam radiotherapy

PURPOSE

Irradiation of choroidal melanoma is a safe and globe preserving procedure. Chronic inflammatory processes and ischemia are the main reasons for secondary enucleation in the long run. The aim of this study was to determine whether intraocular inflammation and especially inflammatory response after proton beam therapy (PBT) is related to primary tumor characteristics such as height, tumor volume, and initial flare values.

METHODS

Twenty-six patients treated for uveal melanoma using PBT were included. All patients were examined for signs of inflammation using laser flare photometry (LFP). Each examination included assessment of the melanoma and fellow eye (which acted as the control) and imaging of the melanoma.

RESULTS

Significant differences of flare values between melanoma eyes and control group were found both at baseline (median 17.65 ph/ms (min 4, max 37.10), 7.45 ph/ms (min 0.80, max 16.40), respectively) and during follow-up (median 21.45 ph/ms (min 4.5, max 70.90); 6.05 ph/ms (min 2.40, max 16.40), respectively) (p < 0.001, Wilcoxon test). Flare values in melanoma eyes increased significantly after PBT (p = 0.005, Wilcoxon test) and after a follow-up of 94 days (median, 7-420 days). Flare values of the control group did not change (p = 0.946, Wilcoxon test). The increase of flare values correlated significantly with maximum tumor height and volume (Spearman-Rho 0.633, p = 0.001 and 0.519, p = 0.007, respectively).

CONCLUSION

LFP has proven to show significantly higher flare values in melanoma eyes as compared with the control group and provides data on the course of the inflammatory response after treatment. It may ease treatment planning both at baseline and during follow-up.

Combined treatment for a large primary cardiac sarcoma: a case report

Background

Undifferentiated pleomorphic sarcoma (UPS) as a primary cardiac tumor is rare, with extremely poor prognosis owing to high recurrence and invasion. We encountered a patient who presented with a primary cardiac tumor incarcerating the mitral valve and who was in a shock state.

Case presentation

A 41-year-old man was transported emergently to our hospital owing to acute respiratory distress and hemoptysis. He was diagnosed with acute left heart failure caused by a large mass in the left atrium (LA) that obstructed cardiac blood flow, as revealed by imaging study findings, and he underwent an emergency open-heart surgery for tumor resection. He was pathologically diagnosed with UPS invading the muscle layer of the LA. However, after receiving combined therapy for local recurrence and distant metastasis, including proton beam radiotherapy and chemotherapy with molecularly targeted drugs, he could return to work for 2 more years after surgery.

Conclusion

In this study, we reported the case of a patient who was in a state of shock state owing to the presence of UPS in the LA. The patient underwent an emergency surgery and received combined therapy. He survived for 2 more years after an initial diagnosis, without active local recurrence and distant metastasis.

Unilateral Multifocal Choroidal Melanoma

We report a case of multifocal choroidal melanoma in the same eye, separated in presentation by 20 years. A 57-year-old Caucasian male initially presented with a choroidal melanoma of the right eye that was treated with transpupillary thermotherapy. Due to recurrence, the patient underwent proton beam therapy with subsequent tumor regression. A second small choroidal lesion was noted in the right eye during his surveillance examinations that was closely monitored and demonstrated stable dimensions and features suggestive of a choroidal nevus. Twenty years after his first presentation, the second lesion exhibited accelerated growth with imaging studies indicative of transformation to a distinct choroidal melanoma. The patient underwent a second globe salvage treatment of proton beam therapy. We describe the clinical course, radiographic, and imaging findings of this rare choroidal melanoma.

Comparison of proton beam radiotherapy and hyper-fractionated accelerated chemoradiotherapy for locally advanced pancreatic cancer

OBJECTIVES

We compared the clinical outcomes of proton beam radiotherapy (PBRT) and those of conventional chemoradiotherapy via hyper-fractionated acceleration radiotherapy (HART) after induction chemotherapy in patients with locally advanced pancreatic cancer (LAPC).

METHODS

Twenty-five consecutive patients with LAPC received induction chemotherapy comprising gemcitabine and S-1 before radiotherapy. Of these, 15 and 10 were enrolled in the HART and PBRT groups, respectively.

RESULTS

Moderate hematological toxicities were observed only in the HART group, whereas two patients in the PBRT group developed duodenal ulcers. All patients underwent scheduled radiotherapy, with overall disease control rates of 93% and 80% in the HART and PBRT groups, respectively. Local progression was observed in 60% and 40% of patients in the HART and PBRT groups, respectively. However, there was no statistical significance between the two groups regarding the median time to progression (15.4 months in both) and the median overall survival (23.4 v.s. 22.3 months).

CONCLUSIONS

PBRT was feasible and tolerable, and scheduled protocols could be completed with careful attention to gastrointestinal ulcers. Despite the lower incidence of local recurrence, PBRT did not yield obvious progression control and survival benefits relative to conventional chemoradiotherapy.

Radiation optic neuropathy and retinopathy with low dose (20 Gy) radiation treatment

Purpose

To report a case of optic neuropathy and retinopathy from a dose of radiation traditionally thought to be safe to the visual system and discuss strategies for preventing vision loss when using radiation to treat intraocular tumors.

Observations

A 44-year-old woman presented with new, painless vision loss in the left eye eighteen months after receiving proton beam radiotherapy (20 Gy dose delivered in two 10 Gy fractions) for a uveal metastasis of lung cancer. The dilated funduscopic examination revealed optic disc swelling and retinal hemorrhages and an MRI of the brain and orbits demonstrated enhancement of the left optic nerve head, findings consistent with radiation optic neuropathy (RON) and retinopathy. Risk factors for developing RON included coincident use of oral chemotherapy and relatively large fractionated doses of radiation.

Conclusions and importance

Though cumulative radiation doses to the anterior visual pathway of less than 50 Gy are traditionally felt to be safe, it is important to consider not just the total exposure but also the size of individual fractions. The single-dose threshold for RON in proton beam treatment has yet to be defined. Our case suggests that fractions of less than 10 Gy should be delivered to minimize the risk of optic nerve injury.

Proton beam radiotherapy of uveal melanoma

Proton beam radiotherapy of uveal melanoma can be administered as primary treatment, as salvage therapy for recurrent tumor, and as neoadjuvant therapy prior to surgical resection. The physical properties of proton beams make it possible to deliver high-doses of radiation to the tumor with relative sparing of adjacent tissues. This form of therapy is effective for a wider range of uveal melanoma than any other modality, providing exceptionally-high rates of local tumor control. This is particularly the case with diffuse iris melanomas, many of which are unresectable. The chances of survival, ocular conservation, visual preservation and avoidance of iatrogenic morbidity depend greatly on the tumor size, location and extent. When treating any side-effects and/or complications, it is helpful to consider whether these are the result of collateral damage or persistence of the irradiated tumor ('toxic tumor syndrome').

Feasibility of proton beam therapy for reirradiation of locoregionally recurrent non-small cell lung cancer

BACKGROUND AND PURPOSE

Options are limited for patients with intrathoracic recurrence of non-small cell lung cancer (NSCLC) who previously received radiation. We report our 5-year experience with the toxicity and efficacy of proton beam therapy (PBT) for reirradiation.

MATERIALS AND METHODS

Thirty-three patients underwent PBT reirradiation for intrathoracic recurrent NSCLC at a single institution. All patients had had RT for NSCLC (median initial dose 63 Gy in 33 fractions), with median interval to reirradiation of 36 months. Median reirradiation dose was 66 Gy (RBE) in 32 fractions. Toxicity was scored with CTCAE v4.0, and survival outcomes were estimated using Kaplan-Meier.

RESULTS

Thirty-one patients (94%) completed reirradiation. At a median 11 months' follow-up, 1-year rates of overall survival, progression-free survival, locoregional control, and distant metastasis-free survival were 47%, 28%, 54%, and 39%. Rates of severe (grade ≥3) toxicity were 9% esophageal, 21% pulmonary; 1 patient had grade 4 esophagitis, and 2 had grade 4 pulmonary toxicity. Nine patients experienced a second in-field failure.

CONCLUSIONS

PBT is an option for treating recurrent NSCLC. However, the rates of locoregional recurrence and distant metastasis are high and the potential for toxicity significant. The risks and benefits of PBT must be carefully weighed in each case.

Tumor Spheroids as an in vitro model for determining the therapeutic response to proton beam radiotherapy and thermally sensitive nanocarriers

Multicellular Tumor Spheroids (MCTS) strongly resemble tumor tissues, which makes them useful tools for radiation biology studies and screening of various chemotherapeutics. The goal of this pilot study was to use MCTS as an in vitro model to determine the response of cells to low temperature-sensitive liposomes (LTSLs) encapsulating doxorubicin (Dox) and proton beam radiotherapy (PBRT). Prior to treatment, MCTS were characterized for morphology and LTSLs were characterized for size, encapsulation efficiency, and ability to thermally release Dox (a model anticancer agent). Two groups of MCTS were treated with LTSL in combination with mild hyperthermia (40-42 °C) or PBRT alone in the presence of appropriate controls. Cytotoxic response was assessed after 48-72 h using an acid phosphatase assay. At 72 h, LTSL in combination with heat significantly reduced the viability of MCTS (15-30%) compared to the control (P < 0.05). A similar cytotoxic response was observed with PBRT treatment. The data suggest that like a monolayer cell culture, MCTS can be used to determine cytotoxic outcomes of thermal and proton therapy.

Phase II trial of proton beam accelerated partial breast irradiation in breast cancer

BACKGROUND AND PURPOSE

Here, we report the results of our phase II, prospective study of proton beam accelerated partial breast irradiation (PB-APBI) in patients with breast cancer after breast conserving surgery (BCS).

MATERIALS AND METHODS

Thirty patients diagnosed with breast cancer were treated with PB-APBI using a single-field proton beam or two fields after BCS. The treatment dose was 30 cobalt gray equivalent (CGE) in six CGE fractions delivered once daily over five consecutive working days.

RESULTS

All patients completed PB-APBI. The median follow-up time was 59 months (range: 43-70 months). Of the 30 patients, none had ipsilateral breast recurrence or regional or distant metastasis, and all were alive at the last follow-up. Physician-evaluated toxicities were mild to moderate, except in one patient who had severe wet desquamation at 2 months that was not observed beyond 6 months. Qualitative physician cosmetic assessments of good or excellent were noted in 83% and 80% of the patients at the end of PB-APBI and at 2 months, respectively, and decreased to 69% at 3 years. A good or excellent cosmetic outcome was noted in all patients treated with a two-field proton beam at any follow-up time point except for one. For all patients, the mean percentage breast retraction assessment (pBRA) value increased significantly during the follow-up period (p=0.02); however, it did not increase in patients treated with two-field PB-APBI (p=0.3).

CONCLUSIONS

PB-APBI consisting of 30 CGE in six CGE fractions once daily for five consecutive days can be delivered with excellent disease control and tolerable skin toxicity to properly selected patients with early-stage breast cancer. Multiple-field PB-APBI may achieve a high rate of good-to-excellent cosmetic outcomes. Additional clinical trials with larger patient groups are needed.