Whole-pelvic radiotherapy with spot-scanning proton beams for uterine cervical cancer: a planning study

Probability of normal tissue complications for hematologic and gastrointestinal toxicity in postoperative whole pelvic radiotherapy for gynecologic malignancies using intensity-modulated proton therapy with robust optimization

This retrospective treatment-planning study was conducted to determine whether intensity-modulated proton therapy with robust optimization (ro-IMPT) reduces the risk of acute hematologic toxicity (H-T) and acute and late gastrointestinal toxicity (GI-T) in postoperative whole pelvic radiotherapy for gynecologic malignancies when compared with three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated X-ray (IMXT) and single-field optimization proton beam (SFO-PBT) therapies. All plans were created for 13 gynecologic-malignancy patients. The prescribed dose was 45 GyE in 25 fractions for 95% planning target volume in 3D-CRT, IMXT and SFO-PBT plans and for 99% clinical target volume (CTV) in ro-IMPT plans. The normal tissue complication probability (NTCP) of each toxicity was used as an in silico surrogate marker. Median estimated NTCP values for acute H-T and acute and late GI-T were 0.20, 0.94 and 0.58 × 10-1 in 3D-CRT; 0.19, 0.65 and 0.24 × 10-1 in IMXT; 0.04, 0.74 and 0.19 × 10-1 in SFO-PBT; and 0.06, 0.66 and 0.15 × 10-1 in ro-IMPT, respectively. Compared with 3D-CRT and IMXT plans, the ro-IMPT plan demonstrated significant reduction in acute H-T and late GI-T. The risk of acute GI-T in ro-IMPT plan is equivalent with IMXT plan. The ro-IMPT plan demonstrated potential clinical benefits for reducing the risk of acute H-T and late GI-T in the treatment of gynecologic malignances by reducing the dose to the bone marrow and bowel bag while maintaining adequate dose coverage to the CTV. Our results indicated that ro-IMPT may reduce acute H-T and late GI-T risk with potentially improving outcomes for postoperative gynecologic-malignancy patients with concurrent chemotherapy.

Outcomes of Proton Beam Therapy Compared With Intensity-Modulated Radiation Therapy for Uterine Cancer

Purpose

To compare Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) in patients with endometrial cancer receiving adjuvant pelvic radiation therapy with proton beam therapy (PT) versus intensity-modulated radiation therapy (IMRT).

Materials and Methods

Patients with uterine cancer treated with curative intent who received either adjuvant PT or IMRT between 2014 and 2020 were identified. Patients were enrolled into a prospective registry using a gynecologic-specific subset of PRO-CTCAE designed to assess symptom impact on daily living. Questions included gastrointestinal (GI) symptoms of diarrhea, flatulence, bowel incontinence, and constipation in addition to other pertinent gynecologic, urinary, and other general symptoms. Symptom-based questions were on a 0- to 4-point scale, with grade 3+ symptoms occurring frequently or almost always. Patient-reported toxicity was analyzed at baseline, end of treatment (EOT), and at 3, 6, 9, and 12 months after treatment. Unequal variance t tests were used to determine if treatment type was a significant factor in baseline-adjusted PRO-CTCAE.

Results

Sixty-seven patients met inclusion criteria. Twenty-two received PT and 45 patients received IMRT. Brachytherapy boost was delivered in 73% of patients. Median external beam dose was 45 Gy for both PT and IMRT (range, 45-58.8 Gy). When comparing PRO-CTCAE, PT was associated with less diarrhea at EOT (P = .01) and at 12 months (P = .24) than IMRT. Loss of bowel control at 12 months was more common in patients receiving IMRT (P = .15). Any patient reporting grade 3+ GI toxicity was noted more frequently with IMRT (31% versus 9%, P = .09).

Discussion

Adjuvant PT is a promising treatment for patients with uterine cancer and may reduce patient-reported GI toxicity as compared with IMRT.

Combined modality management of advanced cervical cancer including novel sensitizers

The management of advanced cervical cancer has evolved with time. Combined modality treatments for cervical cancer have been shown to improve clinical outcomes for these patients. The role of surgery is reviewed in this article for specific situations such as the treatment of bulky lymph nodes and even in the metastatic setting. External beam radiotherapy and brachytherapy techniques have improved which has decreased patient toxicity. Systemic therapy such as chemotherapy, immunotherapy, and novel sensitizing agents have been extensively studied and have shown promising results. The combination of these three different modalities of treatment can be tailored to each specific patient to achieve the best outcomes. We review the recent advances and various international guidelines for the management of cervical cancer in this article.

A patient-specific hybrid phantom for calculating radiation dose and equivalent dose to the whole body

OBJECTIVE

As cancer survivorship increases, there is growing interest in minimizing the late effects of radiation therapy such as radiogenic second cancer, which may occur anywhere in the body. Assessing the risk of late effects requires knowledge of the dose distribution throughout the whole body, including regions far from the treatment field, beyond the typical anatomical extent of clinical CT scans.

APPROACH

A hybrid phantom was developed which consists of in-field patient CT images extracted from ground truth whole-body CT (WBCT) scans, out-of-field mesh phantoms scaled to basic patient measurements, and a blended transition region. Four of these hybrid phantoms were created, representing male and female patients receiving proton therapy treatment in pelvic and cranial sites. To assess the performance of the hybrid approach, we simulated treatments using the hybrid phantoms, the scaled and unscaled mesh phantoms, and the ground truth whole-body CTs. We calculated absorbed dose and equivalent dose in and outside of the treatment field, with a focus on neutrons induced in the patient by proton therapy. Proton and neutron dose was calculated using a general purpose Monte Carlo code.

MAIN RESULTS

The hybrid phantom provided equal or superior accuracy in calculated organ dose and equivalent dose values relative to those obtained using the mesh phantoms in 78% in all selected organs and calculated dose quantities. Comparatively the default mesh and scaled mesh were equal or superior to the other phantoms in 21% and 28% of cases respectively.

SIGNIFICANCE

The proposed methodology for hybrid synthesis provides a tool for whole-body organ dose estimation for individual patients without requiring CT scans of their entire body. Such a capability would be useful for personalized assessment of late effects and risk-optimization of treatment plans.

Dosimetric Comparison of Helical Tomotherapy and Intensity-Modulated Proton Therapy in Hippocampus- and Scalp-Sparing Whole Brain Radiotherapy

Objective: Cognitive decline and alopecia after radiotherapy are challenging problems. We aimed to compare whole brain radiotherapy (WBRT) plans reducing radiation dose to the hippocampus and scalp between helical tomotherapy (HT) and intensity-modulated proton therapy (IMPT). Methods: We conducted a planning study of WBRT for 10 patients. The clinical target volume was defined as the whole brain excluding the hippocampus avoidance (HA) region. The prescribed dose was 30 Gy in 10 fractions to cover 95% of the target. Constraint goals were defined for the target and organs at risk (OAR). Results: Both techniques met the dose constraints for the target and OAR. However, the coverage of the target (dose covering 95% [D95%] and 98% [D98%] of the volume) were better in IMPT than HT (HT vs IMPT: D95%, 29.9 Gy vs 30.0 Gy, P < .001; D98%, 26.7 Gy vs 28.1 Gy, P = .002). The homogeneity and conformity of the target were also better in IMPT than HT (HT vs IMPT: homogeneity index, 1.50 vs 1.28, P < .001; conformity index, 1.30 vs 1.14, P < .001). IMPT reduced the D100% of the hippocampus by 59% (HT vs IMPT: 9.3 Gy vs 3.8 Gy, P < .001) and reduced the Dmean of the hippocampus by 37% (HT vs IMPT: 11.1 Gy vs 7.0 Gy, P < .001) compared with HT. The scalp IMPT reduced the percentage of the volume receiving at least 20 Gy (V20Gy) and V10Gy compared with HT (HT vs IMPT: V20Gy, 56.7% vs 6.6%, P < .001; V10Gy, 90.5% vs 37.1%, P < .001). Conclusion: Both techniques provided acceptable target dose coverage. Especially, IMPT achieved excellent hippocampus- and scalp-sparing. HA-WBRT using IMPT is a promising treatment to prevent cognitive decline and alopecia.

Automated robust SBPT planning using EUD-based prediction of SBRT plan for patients with lung cancer

PURPOSE

To evaluate the quality of robust stereotactic body proton therapy (RSBPT) plans generated by one-clicking scripting method for patients with lung cancer.

MATERIALS AND METHODS

Retrospective analysis was performed on fifty lung cancer patients whose plan with robustly stereotactic body radiation therapy (SBRT). Thirty out of fifty patients were used for training to build a regression model, based on robust SBRT reference doses, to predict EUD values of ROIs for robust SBPT planning. Thereafter, robust SBPT plans with both automated EUD-Based mimicking (Automated Robust Proton ARP) and manual (Manual Robust Proton MRP) methods were evaluated in the remaining 20 patients. Plans were compared in terms of dosimetric parameters and planning time.

RESULTS

A statistically significantly improvement in target dose fall off was observed for ARP plans compare to MRP plans (Dose fall off: 135 for MRP and 88 for ARP, p < 0.01), while no differences in target coverage and conformity. A statistically significantly reduce in normal lung tissue were observed for ARP plans compare to MRP plans (Lung [D_mean cGy (RBE)]: MRP: 478 vs. ARP: 351, p < 0.01; Lung [V_{5Gy (RBE)} (%)]: MRP: 16.1 vs. ARP: 12.1, p < 0.01; Lung [V_{20Gy (RBE)} (%)]: MRP: 8.5 vs. ARP: 6.8, p < 0.01). Planning time was reduced for ARP plans compare to MRP plans (optimization time: 12 min for MRP vs. 8 min for ARP; total plan time: 23 min for MRP vs. 18 min for ARP).

CONCLUSION

The automated robust SBPT plans using EUD-Based mimicking of SBRT reference dose improve target dose fall off, reduced the radiation doses to the lungs, reduce planning time, which might be beneficial for patient with lung cancer in clinical.

Advances in External Beam Radiation Therapy and Brachytherapy for Cervical Cancer

The standard of care for the definitive treatment of locoregionally advanced cervical cancer is external beam radiation therapy (EBRT) with concurrent chemotherapy followed by a brachytherapy boost. Historically, EBRT was delivered via a two-dimensional technique based primarily on bony landmarks. This gave way to three-dimensional conformal radiation therapy, which allows for dose calculation and adjustment based on individual tumour and patient anatomy. Further technological advances have established intensity-modulated radiation therapy (IMRT) as a standard treatment modality, given the ability to maintain tumoricidal doses to target volumes while reducing unwanted radiation dose to nearby critical structures, thereby reducing toxicity. Routine image guidance allows for increased confidence in patient alignment prior to treatment, and the ability to visualise the daily position of the targets and organs at risk has been instrumental in allowing safe reductions in treated volumes. Additional EBRT technologies, including proton therapy and stereotactic body radiation therapy, may further improve the therapeutic index. In the realm of brachytherapy, a shift from point-based dose planning to image-guided brachytherapy has been associated with improved local control and reduced toxicity, with additional refinement ongoing. Here we will discuss these advances, the supporting data and future directions.

Spot Scanning Proton Therapy for Sinonasal Malignant Tumors

Purpose

Treatment of sinonasal malignant tumors is challenging, and evidence to establish a standard treatment is limited. Our objective was to evaluate the efficacy and safety of spot scanning proton therapy (SSPT) for sinonasal malignant tumors.

Patients and Methods

We retrospectively analyzed patients with sinonasal malignant tumors (T1-4bN0-2M0) who underwent SSPT between May 2014 and September 2019. The prescription dose was typically either 60 GyRBE in 15 fractions or 60.8 GyRBE in 16 fractions for mucosal melanoma and 70.2 GyRBE in 26 fractions for other histologic subtypes. Endpoints included local control (LC), progression-free survival, overall survival (OS), and incidence of toxicity. Prognostic factors were analyzed using the Kaplan-Meier method and log-rank test.

Results

Of 62 enrolled patients, the common histologic subtypes were mucosal melanoma (35%), squamous cell carcinoma (27%), adenoid cystic carcinoma (16%), and olfactory neuroblastoma (10%). Locally advanced stages were common (T3 in 42% and T4 in 53%). Treatment-naïve tumors and postsurgical recurrent tumors accounted for 73% and 27%, respectively. No patient had previous radiotherapy. The median follow-up was 17 months (range, 6-66) for all patients and 21.5 months (range, 6-66) for survivors. The 2-year LC, progression-free survival, and OS rates of all patients were 92%, 50%, and 76%, respectively. Univariate analysis revealed histology as a prognostic factor for OS, being higher in adenoid cystic carcinoma and olfactory neuroblastoma than in other tumors. Sixteen grade ≥3 late toxicities were observed in 12 patients (19%), including 11 events resulting in visual impairment; the most common was cataract. There was 1 grade 4 toxicity, and there were no grade 5 toxicities.

Conclusion

SSPT was well tolerated and yielded good LC for sinonasal malignant tumors. Although we consider SSPT to be a leading treatment modality, further studies are required to establish its status as a standard treatment.

Dosimetric Impact of Intrafraction Motion in Online-Adaptive Intensity Modulated Proton Therapy for Cervical Cancer

PURPOSE

A method was recently developed for online-adaptive intensity modulated proton therapy (IMPT) in patients with cervical cancer. The advantage of this approach, relying on the use of tight margins, is challenged by the intrafraction target motion. The purpose of this study was to evaluate the dosimetric effect of intrafraction motion on the target owing to changes in bladder filling in patients with cervical cancer treated with online-adaptive IMPT.

METHODS AND MATERIALS

In 10 patients selected to have large uterus motion induced by bladder filling, the intrafraction anatomic changes were simulated for several prefraction durations for online (automated) contouring and planning. For each scenario, the coverage of the primary target was evaluated with margins of 2.5 and 5 mm.

RESULTS

Using a 5- mm planning target volume margin, median accumulated D98% was greater than 42.75 Gy_RBE1.1 (95% of the prescribed dose) in the case of a prefraction duration of 5 and 10 minutes. For a prefraction duration of 15 minutes, this parameter deteriorated to 42.6 Gy_RBE1.1. When margins were reduced to 2.5 mm, only a 5-minute duration resulted in median target D98% above 42.75 Gy_RBE1.1. In addition, smaller bladders were found to be associated with larger dose degradations compared with larger bladders.

CONCLUSIONS

This study indicates that intrafraction anatomic changes can have a substantial dosimetric effect on target coverage in an online-adaptive IMPT scenario for patients subject to large uterus motion. A margin of 5 mm was sufficient to compensate for the intrafraction motion due to bladder filling for up to 10 minutes of prefraction time. However, compensation for the uncertainties that were disregarded in this study, by using margins or robust optimization, is also required. Furthermore, a large bladder volume restrains intrafraction target motion and is recommended for treating patients in this scenario. Assuming that online-adaptive IMPT remains beneficial as long as narrow margins are used (5 mm or below), this study demonstrates its feasibility with regard to intrafraction motion.

Impact on dose distribution and volume changes of a bioabsorbable polyglycolic acid spacer during chemo-proton therapy for a pediatric Ewing sarcoma

The clinical utility of a recently developed bioabsorbable polyglycolic acid (PGA) spacer has not yet been established in pediatric patients; therefore, we aimed to investigate its utility during chemo-proton therapy for pediatric cancer. Proton depth-dose curves were obtained in a water phantom with or without the spacer. Computed tomography (CT) scans were performed for the PGA spacer immersed in saline for 2 weeks to measure CT numbers and estimate the relative stopping power (RSP) for the proton beams. The spacer was placed in a patient with sacral Ewing sarcoma receiving 55.8 Gy [relative biological effectiveness (RBE)] in 31 fractions and was evaluated using CT scans performed every other week. In addition, the images were used to quantitatively evaluate changes in volume and RSP of the spacer and dose distributions in normal tissues. The spacer immersed in saline had a CT number of 91 ± 7 (mean ± standard deviation) Hounsfield units, and the corresponding RSP was predicted to be 1.07 ± 0.01. The measured RSP agreed with the predicted one. The volumes of the large bowel and rectum receiving ≥45 Gy(RBE) (V45Gy) were significantly reduced by placing the spacer; V45Gy without and with the spacer were 48.5 and 0.01%, respectively, for the rectum and 7.2 and 0%, respectively, for the large bowel. The volume of the spacer and RSP decreased at rates of 4.6 and 0.44% per week, respectively, whereas the target dose coverage was maintained until the end of treatment. The PGA spacer was considered effective for pediatric cancer patients undergoing chemo-proton therapy.

Evaluation of plan quality and robustness of IMPT and helical IMRT for cervical cancer

Background

Both plan quality and robustness were investigated through comparing some dosimetric metrics between intensity modulated proton therapy (IMPT) and helical tomotherapy based intensity modulated radiotherapy (IMRT) for cervical cancer.

Methods

Both a spot-scanning robust (SRO) IMPT plan and a helical tomotherapy robust (TRO) IMRT plan were generated for each of 18 patients. In order to evaluate the quality of nominal plans without dose perturbations, planning scores (PS) on clinical target volume (CTV) and five organs at risk (OARs) based on clinical experience, and normal tissue complication probabilities (NTCP) of rectum and sigmoid were calculated based on Lyman-Kutcher-Burman (LKB) model. Dose volume histogram bands width (DVHBW) were calculated in 28 perturbed scenarios to evaluate plan robustness.

Results

Compared with TRO, the average scores of SRO nominal plans were higher in target metrics [V_46.8Gy, V_50Gy, Conformity and Homogeneity](16.5 vs. 15.1), and in OARs metrics (60.9 vs. 53.3), including bladder [V₃₅,V₄₅, D_mean,D_2cc], rectum [V₄₀,V₄₅,D_2cc,D_max], bowel [V₃₅,V₄₀,V₄₅, D_max], sigmoid [V₄₀,D_max] and femoral heads [V₃₀,D_max]. Meanwhile, NTCP calculation showed that the toxicities of rectum and sigmoid in SRO were lower than those in TRO (rectum: 2.8% vs. 4.8%, p < 0.05; sigmoid: 5.2% vs. 5.7%, p < 0.05). DVHBW in target coverage for the SRO plan was smaller than that for the TRO plan (0.6% vs. 2.1%), which means that the SRO plan generated a more robust plan in target.

Conclusion

Better CTV coverage and OAR Sparing were obtained in SRO nominal plan. Based on NTCP calculation, SRO was expected to allow a small reduction in rectal toxicity. Furthermore, SRO generated a more robust plan in CTV target coverage.

Clinical Evaluation of Onrad, A New Low-cost Version of TomoTherapy that Uses Only Static Beams

OBJECTIVE

This study evaluated the clinical feasibility of a new low-cost TomoTherapy system (Onrad^TM) and compared it with low-cost linear accelerator models (linacs).

METHODS

Various aspects of treatment and cost were compared between Onrad and linacs for 3-dimensional radiotherapy (3DCRT). Dosimetric comparisons of 10 patients each with breast, stage III lung, prostate, head and neck, and cervical cancers were carried out (total 100 plans).

RESULTS

Onrad had advantages in terms of availability of long treatment fields and a smaller mechanical footprint. For breast cancers and lung cancers, target dose homogeneity in Onrad plans was better than that in 3DCRT. In the prostate plans, Onrad plans provided superior D95, conformity and homogeneity. The rectum doses of Onrad plans were lower than those with 3DCRT. Onrad plans provided superior homogeneity and D95 in head and neck cancer. The mean dose and V10-40 Gy of the parotid glands was lower using Onrad. In the cervical cancer plans, target doses were similar with both systems. Normal tissue doses were equal.

CONCLUSIONS

Onrad is useful in the clinical setting. Onrad can achieve favorable or comparable dose distributions compared with those of 3DCRT in actual clinical treatment of breast, lung, prostate, head and neck, and cervical cancers.

Proton therapy for non-squamous cell carcinoma of the head and neck: planning comparison and toxicity

To investigate optimal treatment planning using proton beams for non-squamous cell carcinoma of the head and neck (NSCHN), the dose distributions of plans involving pencil beam scanning (PBS) with or without a patient-specific aperture system (PSAS), passive-scattering proton therapy (PSPT) and X-ray intensity-modulated radiotherapy (IMRT) were compared. As clinical results, toxicities of PBS with PSAS, including changes in quality of life, were reported. Between April 2014 and August 2016, a total of 30 patients were treated using PBS with PSAS. In 20 patients selected at random, the dose distributions of PBS with or without the PSAS, PSPT and IMRT plans were compared. Neutron exposure by proton therapy was calculated using a Monte Carlo simulation. Toxicities were scored according to CTCAE ver. 4.0. Patients completed EORTC quality of life survey forms (QLQ-C30 and QLQ-HN35) before and 0-12 months after proton therapy. The 95% conformity number of PBS with the PSAS plan was the best, and significant differences were detected among the four plans (P < 0.05, Bonferroni tests). Neutron generation by PSAS was ~1.1-fold higher, but was within an acceptable level. No grade 3 or higher acute dermatitis was observed. Pain, appetite loss and increased weight loss were more likely at the end of treatment, but recovered by the 3 month follow-up and returned to the pretreatment level at the 12 month follow-up. PBS with PSAS reduced the penumbra and improved dose conformity in the planning target volume. PBS with PSAS was tolerated well for NSCHN.

Preserving Endocrine Function in Premenopausal Women Undergoing Whole Pelvis Radiation for Cervical Cancer

Purpose

Whole pelvis radiation therapy (WPRT) in premenopausal women with cervical cancer can cause permanent ovarian damage, resulting in premature menopause. Oophoropexy, often considered as an initial step, demonstrates safety of sparing 1 ovary at the cost of delay in initiating WPRT. Therefore, we dosimetrically compared volumetric modulated arc radiotherapy (VMAT) and intensity modulated proton therapy (IMPT) techniques to allow for ovarian-sparing WPRT.

Materials and Methods

Ten patients previously treated for cervical cancer at our institution were included in this institutional review board-approved analysis. A modified clinical treatment volume (CTV) was designed, sparing 1 ovary (left or right), as determined by the physician (ovarian-sparing CTV) and disease extent, including physical exam, positron emission tomography/computed tomography and magnetic resonance imaging. An ovarian-sparing planning target volume was determined as the ovarian-sparing CTV+5 mm for patients who were supine and 7 mm for those who were prone. All plans were calculated to a dose of 45 Gy with specific optimization goals for target volumes, while attempting to maintain a mean ovary dose (D_mean) < 15 Gy. Dosimetric goals were compared across the 2 modalities using the Mann-Whitney U test.

Results

Both treatment modalities were able to achieve primary clinical goal coverage to the uterus/cervix (P = .529, comparing VMAT versus IMPT), ovarian-sparing CTV (P = .796) and ovarian-sparing planning target volume (P = .004). All 10 IMPT plans were able to accomplish the ovary objective (14.0 ± 1.66 Gy). However, only 4 of the 10 VMAT plans were able to achieve a D_mean < 15 Gy to the prioritized ovary, with an average dose of 15.3 ± 4.10 Gy.

Conclusion

Sparing an ovary in women undergoing WPRT for cervical cancer is dosimetrically feasible with IMPT without sacrificing coverage to important clinical targets. Future work will incorporate the brachytherapy dose to the ovarian-sparing CTV and assess the clinical response of this technique as a means to preserve ovarian endocrine function.

Transient increases in serum α fetoprotein and protein induced by vitamin K antagonist II levels following proton therapy does not necessarily indicate progression of hepatocellular carcinoma

Transient increases in α-fetoprotein (AFP) and protein induced by vitamin K antagonist II (PIVKA-II), so-called flares, are frequently observed after treatment of hepatocellular carcinoma (HCC). In the present study, changes in AFP and PIVKA-II levels after proton therapy (PT), and the relationship between the flare phenomenon and clinical response were investigated. In 82 patients with stage I/II HCC (59 with no recurrence and 23 with out-of-field recurrence within 1 year), serum AFP and PIVKA-II levels were measured at 1, 3, 6, 9 and 12 months post-PT. AFP and PIVKA-II flares were defined as a >20% increase from the preceding serum level above 20 ng/ml (AFP) or 40 mAU/ml (PIVKA-II), followed by a >20% drop. Among the 59 patients with no recurrence, 3 (5.1%) had an AFP flare, while 23 (39%) had a PIVKA-II flare. The median time to AFP and PIVKA-II flare peaks was 1 and 6 months, respectively. In 4 patients, PIVKA-II flares were observed twice during follow-up. In 1 patient, AFP and PIVKA-II flares were observed simultaneously at 1 month post-PT. The PIVKA-II level pre-PT was significantly higher in the PIVKA-II flare-positive group compared with that in the flare-negative group (P=0.015, odds ratio 4.3, 95% confidence interval, 1.3-14.0). In the 23 patients with out-of-field recurrence, the median increase rate of PIVKA-II (203%) was higher than that in the PIVKA-II-flare-positive group (111%, P=0.035) and the time to recurrence (median, 9 months) was longer than the time to peak AFP level (1 month) in the AFP-flare-positive group (P=0.033). There was no significant association between flares and clinical response. Increases in AFP and PIVKA-II levels following PT should be assessed with caution to avoid misinterpretation of therapeutic outcome.

Radiation therapy for elderly patients with uterine cervical cancer: feasibility of curative treatment

As the average lifespan lengthens worldwide, and the older adult population increases, the number of elderly patients with uterine cervical cancer is increasing. Because intensive and invasive treatments, including surgery, are frequently unacceptable in elderly patients, cancer treatments for these patients must be carefully considered. Elderly patients have undergone radiation therapy as less-invasive curative treatment, and it has been shown to be safe and effective for local control of cervical cancer in this population, even among patients aged ≥80 years treated with curative radiation doses. Although concurrent chemoradiotherapy is the standard treatment for locally advanced cervical cancer, it is unclear whether the addition of chemotherapy to radiation therapy prolongs survival in elderly patients. Elderly patients treated with curative radiation therapy for cervical cancer might develop more therapy-related gastrointestinal and hematological toxicities and insufficiency fractures compared with younger patients. However, advanced techniques of radiation therapy (eg, intensity-modulated radiation therapy and volumetric modulated arc therapy with photons, charged-particle radiation therapy with protons and carbon ions in external-beam radiation therapy, and image-guided adaptive brachytherapy) can minimize radiation-induced toxicities and thus make curative treatment safer and more effective for elderly patients with uterine cervical cancer.

Effect of a Device-Free Compressed Shell Fixation Method on Hepatic Respiratory Movement: Analysis for Respiratory Amplitude of the Liver and Internal Motions of a Fiducial Marker

PURPOSE

Suppression of respiratory movement of the liver would be desirable for high-precision radiation therapy for liver tumors. We aimed to investigate the effect of our original device-free compressed shell fixation method and breathing instruction on suppression of respiratory movement. The characteristics of liver motion based on the movement of a fiducial marker were also analyzed.

METHODS AND MATERIALS

First, respiratory amplitudes of the liver with the device-free compressed shell were analyzed from the data of 146 patients. The effect of this shell fixing method on liver movement was evaluated. Second, as another cohort study with 166 patients, interfractional internal motion of the liver for patients fixed in the shell was calculated using the fiducial marker coordinate data of images for position setting before daily irradiation. Third, in another 12 patients, intrafractional internal motion was calculated from the fiducial marker coordinate data using x-ray images before and after irradiation.

RESULTS

The median respiratory movement without the shell, after fixing with the shell, and after instructing on the breathing method with the shell was 14.2 (interquartile range, 10.7-19.8), 11.5 (8.6-17.5), and 10.4 mm (7.3-15.8), respectively. Systematic and random errors of interfractional internal motion were all ≤2 mm in the left-right and anteroposterior directions and 3.7 and 3.0 mm, respectively, in the craniocaudal direction. Systematic and random errors of intrafractional internal motion were all ≤1.3 mm in the left-right and anteroposterior directions and 0.8 and 2.4 mm, respectively, in the craniocaudal direction.

CONCLUSIONS

The device-free compressed shell fixation method was effective in suppressing the respiratory movement of the liver. Irradiation position matching using the fiducial marker can correct the interfractional internal motion on each day, which would contribute to the reduction of the margin to be given around the target.

Minimal toxicity after proton beam therapy for prostate and pelvic nodal irradiation: results from the proton collaborative group REG001-09 trial

BACKGROUND

Proton beam therapy (PBT) reduces normal organ dose compared to intensity modulated radiation therapy (IMXT) for prostate cancer patients who receive pelvic radiation therapy. It is not known whether this dosimetric advantage results in less gastrointestinal (GI) and genitourinary (GU) toxicity than would be expected from IMXT.

MATERIAL AND METHODS

We evaluated treatment parameters and toxicity outcomes for non-metastatic prostate cancer patients who received pelvic radiation therapy and enrolled on the PCG REG001-09 trial. Patients who received X-ray therapy and/or brachytherapy were excluded. Of 3210 total enrolled prostate cancer patients, 85 received prostate and pelvic radiation therapy exclusively with PBT. Most had clinically and radiographically negative lymph nodes although 6 had pelvic nodal disease and one also had para-aortic involvement. Pelvic radiation therapy was delivered using either 2 fields (opposed laterals) or 3 fields (opposed laterals and a posterior beam). Median pelvic dose was 46.9 GyE (range 39.7-56) in 25 fractions (range 24-30). Median boost dose to the prostate +/- seminal vesicles was 30 GyE (range 20-41.4) in 16 fractions (range 10-24).

RESULTS

Median follow-up was 14.5 months (range 2.8-49.2). Acute grade 1, 2, and 3 GI toxicity rates were 16.4, 2.4, 0%, respectively. Acute grade 1, 2, and 3 GU toxicity rates were 60, 34.1, 0%, respectively.

CONCLUSIONS

Prostate cancer patients who receive pelvic radiation therapy using PBT experience significantly less acute GI toxicity than is expected using IMXT. Further investigation is warranted to confirm whether this favorable acute GI toxicity profile is related to small bowel sparing from PBT.

Evaluation of dosimetric advantages of using patient-specific aperture system with intensity-modulated proton therapy for the shallow depth tumor

In this study, we evaluate dosimetric advantages of using patient-specific aperture system with intensity-modulated proton therapy (IMPT) for head and neck tumors at the shallow depth. We used four types of patient-specific aperture system (PSAS) to irradiate shallow regions less than 4 g/cm² with a sharp lateral penumbra. Ten head and neck IMPT plans with or without aperture were optimized separately with the same 95% prescription dose and same dose constraint for organs at risk (OARs). The plans were compared using dose volume histograms (DVHs), dose distributions, and some dose indexes such as volume receiving 50% of the prescribed dose (V₅₀ ), mean or maximum dose (D_mean and D_max ) to the OARs. All examples verified in this study had decreased V₅₀ and OAR doses. Average, maximum, and minimum relative reductions of V₅₀ were 15.4%, 38.9%, and 1.0%, respectively. D_max and D_mean of OARs were decreased by 0.3% to 25.7% and by 1.0% to 46.3%, respectively. The plans with the aperture over more than half of the field showed decreased V₅₀ or OAR dose by more than 10%. The dosimetric advantage of patient-specific apertures with IMPT was clarified in many cases. The PSAS has some dosimetric advantages for clinical use, and in some cases, it enables to fulfill dose constraints.

Acute toxicity of image-guided hypofractionated proton therapy for localized prostate cancer

BACKGROUND

Hypofractionated proton therapy (HFPT) is expected to become an effective treatment approach for localized prostate cancer (PCa). The purpose of this study was to evaluate differences in acute toxicity among patients with localized PCa treated with either conventional fractionated proton therapy (CFPT) or HFPT.

METHODS

A total of 526 eligible patients treated with proton therapy between February 2013 and May 2016 in three phase II trials were analyzed. We prescribed 74 gray relative biological effectiveness equivalents [Gy (RBE)]/37 fractions for low-risk patients and 78 Gy (RBE)/39 fractions for intermediate- and high-risk patients in the CFPT group (n = 254) and 60 Gy (RBE)/20 fractions for low-risk and 63 Gy (RBE)/21 fractions for intermediate- and high-risk patients in the HFPT group (n = 272). Patients were evaluated for acute toxicity with the Common Terminology Criteria for Adverse Events, version 4.0, and urinary quality-of-life change using the International Prostate Symptom Score (IPSS).

RESULTS

No grade ≥3 acute toxicity was observed in either group. Among acute genitourinary toxicities, grade 2 rates were 15% (n = 38) in CFPT and 5.9% (n = 16) in HFPT (P ≤ 0.001). The median baseline IPSSs of the CFPT and HFPT groups were 7 (0-29) and 6 (0-31), respectively (P = 0.70). One-month post-treatment scores were 9 (0-32) and 11 (0-32), respectively (P = 0.036), and 6-month post-treatment scores were 7 (0-30) and 7 (0-33), respectively (P = 0.88). There were no significant differences in acute gastrointestinal toxicity between the two groups.

CONCLUSION

Our results demonstrated the safety of HFPT for localized PCa patients in terms of acute toxicity.

Impact of bowel gas and body outline variations on total accumulated dose with intensity-modulated proton therapy in locally advanced cervical cancer patients

INTRODUCTION

Density changes occurring during fractionated radiotherapy in the pelvic region may degrade proton dose distributions. The aim of the study was to quantify the dosimetric impact of gas cavities and body outline variations.

MATERIAL AND METHODS

Seven patients with locally advanced cervical cancer (LACC) were analyzed through a total of 175 daily cone beam computed tomography (CBCT) scans. Four-beams intensity-modulated proton therapy (IMPT) dose plans were generated targeting the internal target volume (ITV) composed of: primary tumor, elective and pathological nodes. The planned dose was 45 Gy [Relative-Biological-Effectiveness-weighted (RBE)] in 25 fractions and simultaneously integrated boosts of pathologic lymph nodes were 55-57.5 Gy (RBE). In total, 475 modified CTs were generated to evaluate the effect of: 1/gas cavities, 2/outline variations and 3/the two combined. The anatomy of each fraction was simulated by propagating gas cavities contours and body outlines from each daily CBCT to the pCT. Hounsfield units corresponding to gas and fat were assigned to the propagated contours. D98 (least dose received by the hottest 98% of the volume) and D99.9 for targets and V43Gy(RBE) (volume receiving ≥43 Gy(RBE)) for organs at risk (OARs) were recalculated on each modified CT, and total dose was evaluated through dose volume histogram (DVH) addition across all fractions.

RESULTS

Weight changes during radiotherapy were between -3.1% and 1.2%. Gas cavities and outline variations induced a median [range] dose degradation for ITV45 of 1.0% [0.5-3.5%] for D98 and 2.1% [0.8-6.4%] for D99.9. Outline variations had larger dosimetric impact than gas cavities. Worst nodal dose degradation was 2.0% for D98 and 2.3% for D99.9. The impact on bladder, bowel and rectum was limited with V43Gy(RBE) variations ≤3.5 cm³.

CONCLUSION

Bowel gas cavities and outline variations had minor impact on accumulated dose in targets and OAR of four-field IMPT in a LACC population of moderate weight changes.

Recovery from sublethal damage and potentially lethal damage : Proton beam irradiation vs. X‑ray irradiation

PURPOSE

In order to clarify the biological response of tumor cells to proton beam irradiation, sublethal damage recovery (SLDR) and potentially lethal damage recovery (PLDR) induced after proton beam irradiation at the center of a 10 cm spread-out Bragg peak (SOBP) were compared with those seen after X‑ray irradiation.

METHODS

Cell survival was determined by a colony assay using EMT6 and human salivary gland tumor (HSG) cells. First, two doses of 4 Gy/GyE (Gray equivalents, GyE) were given at an interfraction interval of 0-6 h. Second, five fractions of 1.6 Gy/GyE were administered at interfraction intervals of 0-5 min. Third, a delayed-plating assay involving cells in plateau-phase cultures was conducted. The cells were plated in plastic dishes immediately or 2-24 h after being irradiated with 8 Gy/GyE of X‑rays or proton beams. Furthermore, we investigated the degree of protection from the effects of X‑rays or proton beams afforded by the radical scavenger dimethyl sulfoxide to estimate the contribution of the indirect effect of radiation.

RESULTS

In both the first and second experiments, SLDR was more suppressed after proton beam irradiation than after X‑ray irradiation. In the third experiment, there was no difference in PLDR between the proton beam and X‑ray irradiation conditions. The degree of protection tended to be higher after X‑ray irradiation than after proton beam irradiation.

CONCLUSION

Compared with that seen after X‑ray irradiation, SLDR might take place to a lesser extent after proton beam irradiation at the center of a 10 cm SOBP, while the extent of PLDR does not differ significantly between these two conditions.