Adaptive radiation therapy of breast cancer by repeated imaging during irradiation

Breast cancer is the most frequent cancer among females and also a leading cause of cancer related mortality worldwide.A multimodality treatment approach may be utilized for optimal management of patients with combinations of surgery,radiation therapy(RT)and systemic treatment.RT composes an integral part of breast conserving treatment,and is typically used after breast conserving surgery to improve local control.Recent years have witnessed significant improvements in the discipline of radiation oncology which allow for more focused and precise treatment delivery.Adaptive radiation therapy(ART)is among the most important RT techniques which may be utilized for redesigning of treatment plans to account for dynamic changes in tumor size and anatomy during the course of irradiation.In the context of breast cancer,ART may serve as an excellent tool for patients receiving breast irradiation followed by a sequential boost to the tumor bed.Primary benefits of ART include more precise boost localization and potential for improved normal tissue sparing with adapted boost target volumes particularly in the setting of seroma reduction during the course of irradiation.Herein,we provide a concise review of ART for breast cancer in light of the literature.

Comparison of Volumetric and Dosimetric Variations in Nasopharyngeal Carcinoma during Intensity-modulated Radiation Therapy with and without Neoadjuvant Chemotherapy

Objective Patients with nasopharyngeal carcinoma(NPC)undergoing intensity-modulated radiation therapy(IMRT)may experience significant volumetric and dosimetric variations throughout the treatment course.However,neoadjuvant chemotherapy may reduce the extent of these variations.This study was carried out to evaluate volumetric and dosimetric changes in target volumes and organs at risk(OARs)during IMRT in patients with locally advanced NPC who received concurrent chemoradiotherapy(CCRT)alone or in combination with neoadjuvant chemotherapy(NACT).Methods 35 NPC patients were recruited for this study and divided into the NACT(n=15)and CCRT(n=20)groups.Computed tomography(CT)scans were performed before neoadjuvant chemotherapy,before IMRT,before the 24 th fraction of IMRT,and after treatment.The original plan(plan 0)was based on CT images collected before IMRT.Hybrid plan 1(plan 1)and hybrid plan 2(plan 2)were generated by applying the beam configurations of plan0 to the CT scans collected before the 24 th fraction of IMRT and after treatment.Volumetric and dosimetric variations were assessed by comparing the results of plan 0 with those of plan 1 and plan 2.Results In the NACT group,compared with that in plan 0,the primary gross tumor volume(GTVnx)decreased by 33.2%±18.4%and 50.5%±12.6%in plan1 and plan 2,respectively.In the CCRT group,the corresponding reduction rates in plan 1 and plan 2 were 49.4%±8.0%and 77.8%±28.1%,respectively.The volume decrease rates in the NACT group were less than those in the CCRT group(P<0.001).In the NACT group,compared with that of plan0,the dose to 95%of the volume(D95)for the planning target volume of the primary tumor(PTVnx)decreased by 1.0%±0.7%and 0.6%±0.6%in plan 1 and plan 2,respectively.In the CCRT group,the corresponding decrease rates in plan 1 and plan 2 were 4.2%±3.8%and 6.1%±6.3%,respectively.The decrease rate of D95 for PTVnx in the NACT group was less than that in the CCRT group(P<0.001).Similar results among the plans were found in terms of D99,Dmean,V93 for PTVnxand PTVnd,and Dmeanfor the parotid glands.Conclusion Neoadjuvant chemotherapy reduces the extent of volumetric and dosimetric variations in target volumes and OARs during IMRT and,thus,helps achieve better target volume coverage,protects adjacent important structures,and minimizes unnecessary replanning during radiotherapy.

Adaptive Dose-Compensation Technique for Image-Guided Radiotherapy of Prostate Cancer

Background: For image-guided radiotherapy(IGRT) of prostate cancer, the current standard is online image guidance which can effectively correct setup errors and inter-fraction rigid organ motion. However, planning margins are still necessary for deformation and intra-fraction motion. Objective: This paper aims to investigate an adaptive planning technique incorporating offline dose feedback to manage interfraction motion and residuals from online corrections. Methods:Repeated CT scans from 28 patients were studied. Online IG was simulated by matching center-of-mass of prostate. A seven-beam IMRT plan with zero margins was designed for each patient. Dose distribution at each fraction was evaluated based on actual target and OARs from that fraction. Cumulative dose was calculated using deformable registration and compared to initial plan. If deviation exceeded pre-defined 2% threshold in prostate D99 an adaptive planning technique called dose compensation was invoked, in which cumulative dose was fed back to the planning system and dose deficit was made up through boost radiation in future fractions through IMRT. Results: If 2% under-dose was allowed at the end of course, then 11 patients failed. If the same criteria was assessed at the end of each week(every 5 fractions), then 14 patients failed. The average dose deficit for these 14 patients was4.4%. They improved to 2% after weekly compensation. 10(out of 14) patients passed criterion after weekly dose compensation; 3 failed marginally; 1 failed significantly(10% deficit). A more aggressive compensation frequency(every 3 fractions) could reduce the dose deficit to the acceptable level for this patient. The doses to OARs were not significantly different from online IG only without dose compensation.Conclusion: We demonstrated an offline dose compensation technique in prostate IGRT which can effectively account for residual uncertainties uncorrectable in online IG. Dose compensation allows further margin reduction and critical organs sparing.

Stereotactic ablative radiotherapy for hepatocellular carcinoma

Patients with hepatocellular carcinoma(HCC)often present with underlying liver disease and significant comorbidities,limiting treatment tolerance.With the development of improved toxicity models and highly conformal radiation delivery systems,external beam radiotherapy has become a valuable treatment option for liver cancer.Using cutting edge technology,stereotactic ablative radiotherapy(SABR)allows for the delivery of ablative doses in few fractions while sparing uninvolved liver tissue.This approach permits dose escalation and precise tumor targeting with minimal risk of radiation induced liver disease.This review clarifies SABR's role alongside liver-directed treatments such as radiofrequency ablation,transarterial radioembolization,and transarterial chemoembolization in the management of HCC.It also examines the promising potential of SABR combined with immunotherapy to treat advanced HCC.