Hadrontherapy for intra- or para-cardiac tumors: evaluation of cardiac radiation dose distribution and acute cardiac effects

Background

There is growing interest in the possibility of using X-rays and hadrons (protons and carbon ions) for antiarrhythmic purposes both at the ventricular and the atrial level, but knowledge about the effects on cardiac tissue outside the target is still limited. Hadron therapy has the dosimetric advantage over photons of a greater ability to concentrate high doses on the target while minimizing the off-target dose. Oncological studies have shown a linear relationship between the mean total heart dose (Dm-heart) of X-rays and the long-term risk of heart damage, particularly when the Dm-heart is>5 Gray (Gy).

Objectives

We designed a prospective study aimed at investigating the effect of heavy particles on cardiac structure and function and on cardiac rhythm in patients undergoing hadrontherapy for intra or para-cardiac tumors.

Methods

Patients candidates to hadrontherapy with a mean predicted cardiac dose grather than zero underwent close cardiological monitoring including blood pressure detection, 12-lead ECG, 12-lead Holter ECG (including time-domain indices of heart rate variability in all cases and Brugada leads in selected cases), cardiac US and cardiac (troponin and natriuretic peptides) and inflammatory biomarkers. These assessments were obtained at baseline, during (ECG and biomarkers only) and at the end of the hadrontherapy cycle, and then every 3–6 months as appropriate. Physicists and radiotherapists collaborated to implement a robust optimization of the treatment plan aimed at minimizing cardiac dose. We present the results of the monitoring up to the end of the hadrontherapy.

Results

17 consecutive patients (56±18 years, range 20–77 years, 59% male) have been enrolled to date, including 3 cases (18%) of intra-cardiac tumors (2 primary and 1 metastatic), who have undergone to 16±6 sessions of radiotherapy each, in 71% of cases with respiratory gating during delivery. Most patients (76%) were treated with carbon ions, the remaining with protons (mean total dose on the neoplastic target 51.8±10.7 Gy, from 2 to 4.2 Gy per fraction). Sixty-one percent of patients had ≥1 cardiovascular risk factor, 6% had a known heart disease (valvular cardiomyopathy despite aortic valve replacement with biological prosthesis and post-surgical pericarditis). The mean dose on the whole heart was 3.58±2.05 Gy, the maximum dose was 33.78±23.99 Gy, with a very variable dose distribution on cardiac substructures depending on the tumor site (table). At the end of the scheduled radiotherapy sessions (24±9 days), no significant changes were observed in cardiac function, cardiac rhythm, ventricular repolarization, biomarkers and autonomic indices.

Conclusions

Hadrontherapy with protons and carbon ions aimed at the treatment of para-cardiac or intra-cardiac tumors allowed to maintain a low heart Dm and showed no signs of acute cardiac toxicity. The collection of potential cardiac effects in the medium and long term is ongoing.

Funding Acknowledgement

Type of funding sources: None.

Dosimetric effect of variable rectum and sigmoid colon filling during carbon ion radiotherapy to sacral chordoma

PURPOSE

Carbon ion radiotherapy (CIRT) is sensitive to anatomical density variations. We examined the dosimetric effect of variable intestinal filling condition during CIRT to ten sacral chordoma patients.

METHODS

For each patient, eight virtual computed tomography scans (vCTs) were generated by varying the density distribution within the rectum and the sigmoid in the planning computed tomography (pCT) with a density override approach mimicking a heterogeneous combination of gas and feces. Totally full and empty intestinal preparations were modelled. In addition, five different intestinal filling conditions were modelled by a mixed density pattern derived from two combined and weighted Gaussian distributions simulating gas and feces respectively. Finally, a patient-specific mixing proportion was estimated by evaluating the daily amount of gas detected in the cone beam computed tomography (CBCT). Dose distribution was recalculated on each vCT and dose volume histograms (DVHs) were examined.

RESULTS

No target coverage degradation was observed at different vCTs. Rectum and sigma dose degradation ranged respectively between: [-6.7; 21.6]GyE and [-0.7; 15.4]GyE for D_50%; [-377.4; 1197.9] and [-95.2; 1027.5] for AUC; [-1.2; 10.7]GyE and [-2.6; 21.5]GyE for D_1%.

CONCLUSIONS

Variation of intestinal density can greatly influence the penetration depth of charged particle and might compromise dose distribution. In particular cases, with large clinical target volume in very close proximity to rectum and sigmoid colon, it is appropriate to evaluate the amount of gas present in the daily CBCT images even if it is totally included in the reference planning structures.

Determination of ion recombination and polarity effect correction factors for a plane-parallel ionization Bragg peak chamber under proton and carbon ion pencil beams

Within the dosimetric characterization of particle beams, laterally-integrated depth-dose-distributions (IDDs) are measured and provided to the treatment planning system (TPS) for beam modeling or used as a benchmark for Monte Carlo (MC) simulations. The purpose of this work is the evaluation, in terms of ion recombination and polarity effect, of the dosimetric correction to be applied to proton and carbon ion curves as a function of linear energy transfer (LET). LET was calculated with a MC code for selected IDDs. Several regions of Bragg peak (BP) curve were investigated. The charge was measured with the plane-parallel BP-ionization chamber mounted in the Peakfinder as a field detector, by delivering a fixed number of particles at the maximum flux. The dose rate dependence was evaluated for different flux levels. The chamber was connected to an electrometer and exposed to un-scanned pencil beams. For each measurement the chamber was supplied with {±400, +200, +100} V. Recombination and polarity correction factors were then calculated as a function of depth and LET in water. Three energies representative of the clinical range were investigated for both particle types. The corrected IDDs (IDD ^k s) were then compared against MC. Recombination correction factors were LET and energy dependent, ranging from 1.000 to 1.040 (±0.5%) for carbon ions, while nearly negligible for protons. Moreover, no corrections need to be applied due to polarity effect being  <0.5% along the whole IDDs for both particle types. IDD ^k s showed a better agreement than uncorrected curves when compared to MC, with a reduction of the mean absolute variation from 1.2% to 0.9%. The aforementioned correction factors were estimated and applied along the IDDs, showing an improved agreement against MC. Results confirmed that corrections are not negligible for carbon ions, particularly around the BP region.

Infections after T-replete haploidentical transplantation and high-dose cyclophosphamide as graft-versus-host disease prophylaxis

BACKGROUND

Recently, a platform of T-cell replete haploidentical hematopoietic stem cell transplantation (haplo-HSCT) using post-transplant cyclophosphamide (Cy) has shown high reproducibility and acceptable safety profile.

METHOD

This prospective cohort analysis allowed us to collect data on infections among 70 consecutive recipients of haplo-HSCT affected by various hematologic malignancies.

RESULTS

After a median follow-up of 23 months, cumulative incidence of viral infections was 70% (95% confidence interval [CI] 59-81) at 100 days and 77% (95% CI 67-87) at 1 year; 35 of 65 patients at risk had CMV reactivation (54%) and the rate of polyomavirus-virus-associated cystitis was 19% (13/70). Cumulative incidence of bacterial and fungal infections at 1 year were 63% (95% CI 51-75) and 12% (95% CI 4-19), respectively. Of note, only 1 invasive fungal infection occurred beyond 1 year after transplant (day +739).

CONCLUSION

In conclusion, despite a high rate of viral infections in the early period, present data suggest a satisfactory infectious profile after T-cell replete haplo-HSCT using post-transplant Cy. These results may help clinicians to improve both prophylactic and therapeutic antimicrobial strategies in this emerging haploidentical setting.