Proton therapy (PT) has been administered for many years to a number of cancers, including brain tumours. Due to their remarkable physical properties, delivering their radiation to a very precise brain volume with no exit dose, protons are particularly appropriate for these tumours. The decrease of the brain integral dose may translate with a diminution of neuro-cognitive toxicity and increase of quality of life, particularly so in children. The brain tumour patient’s access to PT will be substantially increased in the future, with many new facilities being planned or currently constructed in Europe, Asia and the United States. Although approximately 150’000 patients have been treated with PT, no level I evidence has been demonstrated for this treatment. As such, it is this necessary to generate high-quality data and some new prospective trials will include protons or will be activated to compare photons to protons in a randomized design. PT comes however with an additional cost factor that may contribute to the ever-growing health’s expenditure allocated to cancer management. These additional costs and financial toxicity will have to be analysed in the light of a more conformal radiation delivery, non-target brain irradiation and lack of potential for dose escalation when compared to photons. The latter is due to the radiosensitivity of organs at risk in vicinity of the brain tumour, that photons cannot spare optimally. Consequentially, radiation-induced toxicities and tumour recurrences, which are cost-intensive, may decrease with PT resulting in an optimized photon/proton financial ratio in the end. Advances in knowledge: This review details the indication of brain tumors for proton therapy and give a list of the open prospective trials for these challenging tumors.

Objective: To assess the radiation-induced optic neuropathy (RION) prevalence, following high dose pencil beam scanning proton therapy (PBSPT) to skull base and head and neck (H&N) tumours Methods: Between 1999 and 2014, 216 adult patients, median age 47 years (range, 18–77), were treated with PBS PT for skull base or H&N malignancies, delivering ≥45 GyRBE to the optic nerve(s) (ON) and/or optic chiasma (OC). The median administered dose to the planning target volume was 74.0 GyRBE (range, 54.0–77.4). The median follow-up was 5.3 years (range, 0.8–15.9). Results: RION was observed in 14 (6.5%) patients at a median time of 13.2 months (range, 4.8–42.6) following PBSPT. Most (92.9%) of RION were symptomatic. Most affected patients (11/14; 79%) developed unilateral toxicity. Grade 4, 3, 2 and 1 toxicity was observed in 10, 2, 1 and 1 patients, respectively. On univariate analyses, age (<70 vs ≥70 years; p < 0.0001), hypertension (p = 0.0007) and tumour abutting the optic apparatus (p = 0.012) were associated with RION. OC’s V60 GyRBE was of border line significance (p = 0.06). None of the other evaluated OC–ON dose/volume metrics (Dmax, Dmean, V40-60) were significantly associated with this complication. Conclusion: These data suggest that high-dose PBS PT for skull base and H&N tumours is associated with a low prevalence of RION. Caution should be however exercised when treating elderly/hypertensive patients with tumours abutting the optic apparatus. Advances in knowledge: This is the first study reporting the risk of developing RION following proton therapy with PBS technique, demonstrating the safety of this treatment.

Objective: Large inoperable sacral chordomas show unsatisfactory local control rates even when treated with high dose proton therapy (PT). The aim of this study is assessing feasibility and reporting early results of patients treated with PT and concomitant hyperthermia (HT). Methods: : Patients had histologically proven unresectable sacral chordomas and received 70 Gy (relative biological effectiveness) in 2.5 Gy fractions with concomitant weekly HT. Toxicity was assessed according to CTCAE_v4. A volumetric tumor response analysis was performed. Results: : Five patients were treated with the combined approach. Median baseline tumor volume was 735 cc (range, 369–1142). All patients completed PT and received a median of 5 HT sessions (range, 2–6). Median follow-up was 18 months (range, 9–26). The volumetric analysis showed an objective response of all tumors (median shrinkage 46%; range, 9–72). All patients experienced acute Grade 2–3 local pain. One patient presented with a late Grade 3 iliac fracture. Conclusion: Combining PT and HT in large inoperable sacral chordomas is feasible and causes acceptable toxicity. Volumetric analysis shows promising early results, warranting confirmation in the framework of a prospective trial. Advances in knowledge: : This is an encouraging first report of the feasibility and early results of concomitant HT and PT in treating inoperable sacral chordoma.

Background: Proton therapy is indicated for cancers that would be difficult to treat with conventional radiotherapy. Compulsory healthcare insurance covers the costs of this therapy in Switzerland, but this does not mean that proton therapy is cost-neutral for every cancer patient. Significant out-of-pocket (OOP) costs may arise due to expenses associated with proton therapy, and patients may experience treatment-related financial distress—an effect known as “financial toxicity.” This study investigates the financial toxicity of patients undergoing proton therapy in a high-income country with a compulsory health insurance policy. Methods: Between September 2019 and November 2021, 146 Swiss cancer patients treated with proton therapy participated in this study, of whom 90 (62%) were adults and 56 (38%) were caregivers of child cancer patients. Financial toxicity was assessed using the FACIT Comprehensive Score for Financial Toxicity (COST). OOP costs during proton therapy were recorded weekly, and financial coping strategies were captured at the end of treatment. Findings: The median COST score, indicating financial toxicity, was 29.9 (IQR 21.0; 36.0) for all patients, 30.0 (IQR 21.3; 37.9) for adults, and 28.0 (IQR 20.5; 34.0) for children’s caregivers. Higher income (estimate 8.1, 95% CI 3.7 to 12.4, p ≤ 0.001) was significantly associated with higher COST scores, indicating less financial toxicity. Further distance from home to the treatment centre per 100 km (estimate −3.7, 95% CI −5.7 to −1.9, p ≤ 0.001) was significantly associated with lower COST scores, indicating increased financial toxicity. Married adult patients had substantially lower COST scores than single patients (estimate: −9.1, 95% CI −14.8 to −3.4, p ≤ 0.001). The median OOP cost was 2050 Swiss francs (CHF) and was spent mainly on travel, accommodation, and eating out. Sixty-three (43%) patients used their savings; 54 (37%) cut spending on leisure activities; 21 (14.4%) cut living expenses; 14 (9.6%) borrowed money; nine (6.2%) worked more; and four (2.7%) sold property. Patients with high COST scores used significantly fewer coping strategies such as saving on leisure activities (estimate −9.5, 95% CI −12.4 to −6.6, p ≤ 0.001), spending savings (estimate −3.9, 95% CI −6.3 to −1.4, p = 0.002), borrowing money (estimate −6.3, 95% CI −10.4 to −2.2, p = 0.003), and increasing workload (estimate −5.5, 95% CI −10.5 to −0.4, p = 0.035). Interpretation: A substantial number of cancer patients treated with proton therapy experience financial toxicity in Switzerland. Long travel distances to the proton therapy centre and low income negatively affect the financial well-being of these patients during proton therapy.

To assess the incidence and severity of changes in hearing threshold in patients undergoing high-dose pencil-beam-scanning proton therapy (PBS-PT). This retrospective cohort study included fifty-one patients (median 50 years (range, 13–68)) treated with PBS-PT for skull base tumors. No chemotherapy was delivered. Pure tone averages (PTAs)were determined before (baseline) and after PBS-PT as the average hearing thresholds at frequencies of 0.5, 1, 2, and 4 kHz. Hearing changes were calculated as PTA differences between pre-and post-PBS-PT. A linear mixed-effects model was used to assess the relationship between the PTA at the follow-up and the baseline, the cochlea radiation dose intensity, the increased age, and the years after PBS-PT. Included patients were treated for chordoma (n = 24), chondrosarcoma (n = 9), head and neck tumors (n = 9), or meningioma (n = 3), with a mean tumor dose of 71.1 Gy (RBE) (range, 52.0–77.8), and a mean dose of 37 Gy (RBE) (range, 0.0–72.7) was delivered to the cochleas. The median time to the first follow-up was 11 months (IQR, 5.5–33.7). The PTA increased from a median of 15 dB (IQR 10.0–25) at the baseline to 23.8 (IQR 11.3–46.3) at the first follow-up. In the linear mixed-effect model, the baseline PTA (estimate 0.80, 95%CI 0.64 to 0.96, p ≤ 0.001), patient’s age (0.30, 0.03 to 0.57, p = 0.029), follow-up time (2.07, 0.92 to 3.23, p ≤ 0.001), and mean cochlear dose in Gy (RBE) (0.34, 0.21 to 0.46, p ≤ 0.001) were all significantly associated with an increase in PTA at follow-up. The applied cochlear dose and baseline PTA, age, and time after treatment were significantly associated with hearing loss after proton therapy.

Standard care for head and neck cancer (HNC) treatment with proton therapy typically involves a 4–6 field Intensity Modulated Proton Therapy plan to enhance robustness towards anatomical changes and patient misalignments. This study aimed to evaluate whether a more efficient plan with fewer beams, designed for faster delivery, can be combined with online daily adaptation (DAPT) to provide treatment of comparable quality, and improve treatment outcomes. We retrospectively analyzed five HNC patients with available daily 3D imaging treated at our institution. To simulate DAPT, synthetic Computed Tomography (CT) images were generated by deforming planning CT to each daily Cone-Beam CT with targets and organs-at-risk (OARs) propagated to daily images. Three plans were created per-patient: Offline_SBC and DAPT_SBC with standard, and DAPT_RBC with reduced, beam configuration. DAPT_SBC and DAPT_RBC were reoptimized on daily synCTs, while Offline_SBC followed clinical workflow, with offline replanning as needed. Offline_SBC showed >5% target underdosage in 15% of fractions, with both adaptive approaches significantly improving coverage. Although DAPT_RBC outperformed Offline_SBC for target coverage, its advantage in OARs sparing was less definitive. DAPT_SBC reduced pooled average normal tissue dose across patients and fractions by 13% and pooled average normal tissue complication probability for xerostomia by 7%. Delivery of DAPT_RBC with fewer beams was 24% faster than plans with conventional arrangement. Our delivery efficiency study shows that DAPT can allow fewer beams to achieve faster delivery, as shown in case of DAPT_RBC workflow, and a reduction in the dose to normal tissue.