Proton Beam Therapy for Thymic Carcinoma with Pericardial Involvement

Dosimetric superiority of deep inspiration breath hold-proton beam therapy for cardiac metastasis

The purpose of this case report is to compare the dosimetric disparities between photon radiotherapy and intensity-modulated proton therapy (IMPT) with or without deep inspiration breath hold (DIBH) for cardiac tumors. We present a case involving a 66-year-old female with cardiac metastasis from thymic carcinoma. A total dose of 50Gy/50Gy(RBE) in 25 fractions was administered to the cardiac metastases. Two simulation CT scans were obtained during free breath (FB) and DIBH. Dose distribution to target and organs at risk(OARs) was compared between intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT) and IMPT. All of the 6 plans satisfied treatment planning goals. The coronary artery (CA) Dmean (mean dose) was 28.32 Gy for IMRT-DIBH, 42.66 Gy for IMRT-FB, 26.44 Gy for VMAT-DIBH, 40.85 Gy for VMAT-FB, 27.71 Gy for IMPT-DIBH, and 39.51 Gy for IMPT-FB. The heart V50 (volume receiving ≥50 Gy) was 3.90 Gy for IMRT-DIBH, 6.71 Gy for IMRT-FB, 4.80 Gy for VMAT-DIBH, 6.63 Gy for VMAT-FB, 0.99 Gy for IMPT-DIBH, and 6.67 Gy for IMPT-FB, respectively. DIBH resulted in dose reductions in all OARs, particularly the heart and CA, compared to FB in all 3 planning techniques (IMRT, VMAT, and IMPT). Similarly, compared with IMRT or VMAT, IMPT reduced radiation doses to most OARs, including the heart and CA, in both FB and DIBH. DIBH-IMPT demonstrated superior dose coverage and OARs sparing in this thymic carcinoma patient with cardiac metastasis. Given the anticipated reduction in toxicities, IMPT with DIBH is preferred for cardiac tumors. The potential for broader application of IMPT with DIBH in clinical practice is currently being evaluated, and further studies are needed.

Hadrontherapy for Thymic Epithelial Tumors: Implementation in Clinical Practice

Radiation therapy is part of recommendations in the adjuvant settings for advanced stage or as exclusive treatment in unresectable thymic epithelial tumors (TETs). However, first-generation techniques delivered substantial radiation doses to critical organs at risk (OARs), such as the heart or the lungs, resulting in noticeable radiation-induced toxicity. Treatment techniques have significantly evolved for TET irradiation, and modern techniques efficiently spare normal surrounding tissues without negative impact on tumor coverage and consequently local control or patient survival. Considering its dosimetric advantages, hadrontherapy (which includes proton therapy and carbon ion therapy) has proved to be worthwhile for TET irradiation in particular for challenging clinical situations such as cardiac tumoral involvement. However, clinical experience for hadrontherapy is still limited and mainly relies on small-size proton therapy studies. This critical review aims to analyze the current status of hadrontherapy for TET irradiation to implement it at a larger scale.