Is there room for combined modality treatments? Dosimetric comparison of boost strategies for advanced head and neck and prostate cancer

Abstract

The purpose of the study was to determine the dosimetric difference between three emerging treatment modalities—volumetric-modulated arc therapy (VMAT), intensity-modulated proton beam therapy (IMPT) and intensity-modulated carbon ion beam therapy (IMIT)—for two tumour sites where selective boosting of the tumour is applied. For 10 patients with locally advanced head and neck (H&N) cancer and 10 with high-risk prostate cancer (PC) a VMAT plan was generated for PTVinitial that included lymph node regions, delivering 50 Gy (IsoE) for H&N and 50.4 Gy (IsoE) for PC patients. Furthermore, separate boost plans (VMAT, IMPT and IMIT) were created to boost PTVboost up to 70 Gy (IsoE) and 78 Gy (IsoE) for H&N and PC cases, respectively. Doses to brainstem, myelon, larynx and parotid glands were assessed for H&N cases. Additionally, various OARs (e.g. cochlea, middle ear, masticator space) were evaluated that are currently discussed with respect to quality of life after treatment. For PC cases, bladder, rectum and femoral heads were considered as OARs. For both tumour sites target goals were easily met. Looking at OAR sparing, generally VMAT + VMAT was worst. VMAT + IMIT had the potential to spare some structures in very close target vicinity (such as cochlea, middle ear, masticator space ) significantly better than VMAT + IMPT. Mean doses for rectal and bladder wall were on average 4 Gy (IsoE) and 1.5 Gy (IsoE) higher, respectively, compared to photons plus particles scenarios. Similar results were found for parotid glands and larynx. Concerning target coverage, no significant differences were observed between the three treatment concepts. Clear dosimetric benefits were observed for particle beam therapy as boost modality. However, the clinical benefit of combined modality treatments remains to be demonstrated.

Toll-Like Receptors and Prostate Cancer

“…A wave of preclinical and clinical studies showed the potential of developing treatment targeting TLRs against prostate cancer. Based on these researches, one of the most probable approaches is to use agents targeting TLRs as adjuvants along with other treatments ( 67 , 68 , 71 , 77 , 78 ). Above all, elucidation of the mechanisms of cancer cell TLR signaling and crosstalk with other signaling pathways as well as the mechanisms of cancer progression will definitely provide a promising novel strategy for cancer treatment.…”

Enhanced radiobiological effects at the distal end of a clinical proton beam: in vitro study

“…In recent years, advanced proton therapy [e.g. intensity-modulated proton therapy (IMPT)] has been adapted for irregularly shaped tumors, and the effect is beginning to examined by physical fundamental research [ 5 , 6 , 8 , 9 ]. The International Commission on Radiation Units and Measurements (ICRU) recommends defining proton therapy doses as the product of the relative biological effectiveness (RBE) and the physical dose of the proton, with its unit as Gy [ 11 , 12 ].…”

Comparative dosimetrical analysis of intensity-modulated arc therapy, CyberKnife therapy and image-guided interstitial HDR and LDR brachytherapy of low risk prostate cancer

“…EQD2 D50 to DIL were 110.7 Gy, 114.2 Gy and 150.1 Gy in IMAT, proton therapy and HDR BT plans, while the mean dose of the rectal wall was 30.5 Gy, 16.7 Gy and 9.5 Gy, and the mean dose to the bladder wall were 21.0 Gy, 15.6 Gy and 6.3 Gy, respectively. Georg et al examined the optimal radiotherapy technique in the radiotherapy of localised prostate cancer and stated that HDR and LDR BT techniques were clearly superior in terms of the bladder and rectal wall sparing, in contrast with IMAT, proton-and carbon-ion therapy, with the lowest values for HDR BT [2]. However, they did not examine the dose to the urethra.…”

“…It is estimated that 33,000 deaths from this disease will occur this year [1]. The standard of care in the curative treatment of low-and selected intermediate-risk prostate cancer is external beam radiotherapy with intensity-modulated arc therapy (IMAT) or with CyberKnife (CK) technique or interstitial high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy (BT) [2].…”

“…Andrzejewski et al studied the feasibility of dominant intraprostatic lesion (DIL) boosting using IMAT, proton therapy or HDR BT for 12 patients [15]. Georg et al examined the optimal radiotherapy technique among IMAT, proton-, carbon-ion therapy and HDR or LDR BT, but HDR BT was not a single fraction monotherapy for the 10 studied patients [2]. Morton et al studied HDR and LDR BT techniques against IMAT external beam therapy [16].…”