**7. Treatment strategies of RRHD**

proton RT could reduce the maximal dose, V20Gy, V5Gy, etc [49–52]. However, because of the limited availability and high cost, at present, this technique is not advocated for cardiac dose

For Hodgkin lymphoma, the RT field has changed over the past decades. Previously, the majority of patients received mantle field radiation with/without upper abdomen field radiation, and a large volume of the heart had a prescribed dose irradiation. According to the anatomical sites of disease presence, the caudal border of the mantle field individually varied from the bottom border at the 8th–9th thoracic vertebrae (T8–T9) [53] to T10–T11 [54, 55], and the higher caudal border might spare most of the irradiated heart volume [53]. With advanced imaging modalities such as positron emission tomography–CT and improved RT delivery techniques such as IMRT, image-guided RT, and breath control techniques, among others, the previously applied extended field and involved field techniques have now been replaced by techniques using limited target volumes, such as involved node RT (INRT) and involved site RT (ISRT) [56]. With the optimal imaging during the course of treatment, both the INRT and ISRT techniques reduce the treated volume to a safe minimum [56]. In addition, with refinements of Hodgkin lymphoma, the prescription dose decreased to 20–36 Gy [57]. Due to more limited target volume and lower prescribed radiation doses, greater amounts of normal healthy tissues such as lung and heart could

Theoretically, for RT of non-small cell lung cancer, dose escalation to 74 Gy would be better than the standardized 60 Gy dose. However, the results of a randomized phase 3 study (RTOG 0617) showed that a higher dose did not translate to a better outcome and might even be potentially harmful [58]. One reasonable explanation is that patients receiving doses of 74 Gy usually had worse dose-volume effects on the heart. The dose volume parameters including V5Gy and V30Gy of the heart were the important predictors of patient survival [58]. The dose-volume effects on the heart substructures such as the pericardium, atria, and ventricles will be investigated and their dose-volume limitations will be included in future lung cancer trials. In addition, for early and locally advanced non-small cell lung cancer, proton RT

**6. Radiation for patients with cardiac implantable electronic devices**

The numbers of patients with both cardiac implantable electronic devices (CIEDs) including pacemakers (PMs) and implantable cardiac defibrillators and cancer are expected to rise, and patients in these situations require RT. The potential interactions between high doses of radiation and the function, longevity, and integrity of the CIEDs, as well as the harm to the patients, remain unclear. The results of a recent review [60, 61] showed that the risk of device failure increases with increasing radiation doses, without a clear cutoff point. For patients with pacemakers, the delivered total radiation dose to the device was strongly recommended not to exceed 2 Gy and the dose in patients with implantable cardiac defibrillators should be

sparing [36].

200 Radiotherapy

be spared.

will potentially be used for cardiac sparing [59].

Generally, the treatment strategies of various RRHDs are similar to those in normal population [62–64]. For example, radiation-induced left ventricular dysfunction or heart failure could be treated according to the recommended guidelines of heart failure [65]. And for those with anticancer drug-induced hypertension, antihypertensive agents should be individualized to the clinical circumstances of the patients [66]. Angiotensinconverting enzyme inhibitors or angiotensin II receptor blockers are usually considered for patients with proteinuria, metabolic syndrome, or high risk of chronic kidney disease [66]. Treatment with nondihydropyridine calcium channel blockers should be avoided in patients receiving cytochrome P450 inhibitors, while dihydropyridine calcium channel blockers are preferred in elderly patients [67, 68]. Low-molecular weight heparin for a minimum of 3–6 months is the recommended treatment for patients with newly diagnosed venous thromboembolism [69].
