Background: This study aims to compare retrospectively generated gated internal target volumes (ITVs) and to evaluate whether gated ITVs can reduce planned target volumes (PTVs) compared with standard ITV expansions. Materials and Methods: In this study, we retrospectively generated respiratory-gated ITVs and PTVs for our cohort of patients who underwent four-dimensional computed tomography for thoracic radiotherapy in our department between August 2018 and February 2019. We calculated the standard ITVs and two gated ITVs to analyze the volumetric reduction. Further, we considered a PTV reduction of >10% to be significant, and we analyzed the role of the localization and the size of the gross tumor volumes. Results: We included 38 patients with a median age of 70 years (mean = 68, SD ± 13,4, range =43–89), of whom 18 (47%) were females and 20 (52%) were males. The two gated PTVs (PTV 30%–70% and PTV 80%–20%) were significantly smaller than the standard PTVs (p-value < 0,001 for both PTVs). Considering the volume of the gross target volume (GTV), we found a significant correlation between GTV30cc and ITV30%–70% (chi-square analysis, p:0,006) and between GTV5cc and ITV80%–20% (p:0,003). We also found a correlation between the localization of the target lesion (mediastinal/central/peripheral lesion) for both the gated ITVs (p: 0,030 for ITV 30%–70% and p:0,018 for ITV 80%–20%). Conclusion: Gated ITV plans could be useful for the sparing of normal tissues. Our results show that this approach could be useful for small lesions and for certain localizations (island tumors).

Background: We report a case of a metastatic breast cancer woman undergoing therapy with fulvestrant and palbociclib that was successfully treated with thoracic stereotactic ablative radiation therapy (SABR) for a hilar lymph node metastasis. Case Description: The patient began the radiation treatment in the week off of the palbociclib and reported no acute toxicity. The CT scan showed acute pneumonia 60 days after RT although the patient reported no symptomatology. In addition, the subsequent PET/TC scan performed six months after RT exhibited a complete response of the irradiated lesion. Conclusion: The use of SABR in patients undergoing cyclin inhibitors appears to be potentially effective although the association must be further studied to investigate the toxicities.