Retrospective comparison of rectal toxicity between carbon-ion radiotherapy and intensity-modulated radiation therapy based on treatment plan, normal tissue complication probability model, and clinical outcomes in prostate cancer

Assessment of rectal toxicities after radiation therapy for localized prostate cancer: experience of the Akanda Cancer Institute in Gabon

Background

The purpose was to evaluate the incidence of acute and late rectal toxicities and their correlation with the clinical and dosimetric parameters of patients who underwent curative radiotherapy for localized prostate cancer at the Akanda Cancer Institute, Gabon.

Materials and methods

Between 2013 and 2021, a cohort of 46 patients with clinically localized stage cT1c-T4 prostate cancer was treated with three-dimensional conformal radiation therapy (3D-CRT) at the national cancer institute with doses ranging from 66 to 80 Gy. Post-radiation gastrointestinal (GI) toxicities were classified and graded according to the Common Terminology Criteria for Adverse Events CTCAE v4.0.

Results

In our study, 17.4% (8/46) developed acute GI. Grades 1 and 3 acute GI complications were seen in 13.0% (6/46) and 4.3% (2/46), respectively. No patient developed acute grade 2 or grade higher than 3 complications. Late GI side effects were limited. The median time to the development of late GI Grade ≥ 1 toxicities was 12 months (range: 9-19 months). 10.9% (5/46) had experience late GI. Among them, grade 1 and 2 were seen in 6.5% (3/46), and 4.3% (2/46), respectively. There was no grade 3 or higher complications. Statistically, we did not find any correlation between the presence of rectal toxicity and clinical factors or the presence of comorbidity. On the dosimetric level, the Mann-Whitney statistical test found a correlation between the presence of late GI toxicity and rectal volume irradiated at the prescribed dose (p = 0.02).

Conclusion

Despite the high radiation doses involved, our results showed an acceptable complication rate.

Normal tissue complication probability of acute eyelids erythema following radiotherapy of head and neck cancers and skull-base tumors

PURPOSE

Radiation therapy is broadly used as one of the main treatment methods for patients with head and neck cancers and skull base tumors. However, it can lead to normal tissue complications. Therefore, this study aimed to model normal tissue complication probability (NTCP) of eyelid skin erythema after radiation therapy.

METHODS

The dataset of 45 patients with head and neck and skull base tumors was prospectively collected from their dose-volume histograms (DVHs). Grade 1 + eyelid skin erythema based on the Common Terminology Criteria for Adverse Events (CTCAE 4.0) was evaluated as the endpoint after a three-month follow-up. The Lyman-Kutcher-Burman (LKB) radiobiological model was developed based on generalized equivalent uniform dose (gEUD). Model parameters were calculated by maximum likelihood estimation. Model performance was evaluated by ROC-AUC, Brier score and Hosmer-Lemeshow test.

RESULTS

After three months of follow-up, 13.33% of patients experienced eyelids skin erythema grade 1 or more. The parameters of the LKB model were: TD50 = 30 Gy, m = 0.14, and n = 0.10. The model showed good predictive performance with ROC-AUC = 0.80 (CI:0.66-0.94) and a Brier score of 0.20.

CONCLUSIONS

In this study, NTCP of eyelid skin erythema was modeled based on the LKB radiobiological model with good predictive performance.

Ways to unravel the clinical potential of carbon ions for head and neck cancer reirradiation: dosimetric comparison and local failure pattern analysis as part of the prospective randomized CARE trial

Background

Carbon ion radiotherapy (CIRT) yields biophysical advantages compared to photons but randomized studies for the reirradiation setting are pending. The aim of the current project was to evaluate potential clinical benefits and drawbacks of CIRT compared to volumetric modulated arc therapy (VMAT) in recurrent head and neck cancer.

Methods

Dose-volume parameters and local failure patterns of CIRT compared to VMAT were evaluate in 16 patients from the randomized CARE trial on head and neck cancer reirradiation.

Results

Despite an increased target dose, CIRT resulted in significantly reduced organ at risk (OAR) dose across all patients (− 8.7% Dmean). The dose-volume benefits were most pronounced in the brainstem (− 20.7% Dmax) and the optic chiasma (− 13.0% Dmax). The most frequent local failure was type E (extraneous; 50%), followed type B (peripheral; 33%) and type A (central; 17%). In one patient with type A biological and/or dosimetric failure after CIRT, mMKM dose recalculation revealed reduced target coverage.

Conclusions

CIRT resulted in highly improved critical OAR sparing compared to VMAT across all head and neck cancer reirradiation scenarios despite an increased prescription dose. Local failure pattern analysis revealed further potential CIRT specific clinical benefits and potential pitfalls with regard to image-guidance and biological dose-optimization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-02093-4.