Particle Beam Therapy and Surgery as Radical Treatments for Parotid Malignancies-A Single-Center Preliminary Case Study.

Background/Objectives: Particle beam therapy (PBT) was approved in April 2018 for head and neck malignancies and has since been introduced as a radical therapy for parotid malignancies. However, its prevalence and effectiveness in relation to surgical treatment have not been investigated. Methods: In this study, we evaluated 36 patients with parotid malignancy who underwent surgery (n = 26) or PBT (n = 10) and then analyzed the annual changes in the number of patients, survival rates, and clinical factors affecting prognosis. Results: Of the ten patients who opted for PBT, two and eight patients underwent PBT before and after 2018, respectively. There was a significant difference between these two groups of patients (p = 0.04). Of the ten patients who underwent PBT, five patients were recurrent cases; meanwhile, all twenty-six patients who underwent surgery were receiving initial treatment. Only one patient in each group had local recurrence after the treatment. Conclusions: The use of PBT as a radical therapy for parotid malignancies has been increasing since 2018, and patients with recurrent tumors tended to choose PBT. The outcome of the patients who underwent PBT did not seem to be inferior compared with those of the patients who underwent surgery. The histopathological type was a crucial issue in the outcomes of patients who underwent radical therapy for parotid malignancies.

Development of a dose-rate dosimeter using a silicon photodiode for a medical linear accelerator in a 10 MV flattening filter-free mode.

This study was aimed at developing a dose-rate dosimeter to measure the instantaneous dose rate of a commercially available medical linear accelerator. A dose-rate dosimeter composed of a silicon photodiode (Si-PD), a complementary metal-oxide semiconductor single operational amplifier, a resistor of 20 MΩ, a capacitor of 100 pF, and a mini-substrate measuring 16 × 16 mm2 was evaluated. Voltage outputs from the proposed dosimeter were measured using an analog-to-digital converter on a microcomputer. A custom-made x-ray tube generator at an energy of 120 kV with a tube current ranging from 0.1 to 2.0 mA was used for the dose-rate calibration. Dose-rate calibration was performed 83.3 mm from an x-ray source using a commercially available semiconductor dosimeter. The developed Si-PD dosimeter could measure up to 0.6 Gy/s at a distance of 19.3 mm from the x-ray source. Measurements were also performed using a medical linear accelerator in a 10 MV flattening filter-free mode at depths of 0, 25, 50, and 100 mm with an irradiation field of 100 × 100 mm2 at a constant distance of 1000 mm from the source to the dosimeter. A peak voltage variation corresponding to the instantaneous dose rate was observed using a sampling period of 1.0 ms, and the peak voltages decreased with the depth. The detected pulse numbers were 512, 484, 491, and 511 at depths of 0, 25, 50, and 100 mm, respectively.

Increasing Patients With HPV-positive Oropharyngeal Squamous Cell Carcinoma and its Oncologic Outcomes in the Rural Region in Northern Japan.

BACKGROUND/AIM: Despite the global rise in the incidence of human papillomavirus (HPV)-positive oropharyngeal carcinoma (OPC) in recent years, its prevalence and oncological outcomes in patients living in rural areas of Northern Japan has not been explored and should be investigated. PATIENTS AND METHODS: A total of 105 patients with oropharyngeal squamous cell carcinoma who underwent HPV screening and received first-line treatment were included in this study. The annual changes in the number of patients, survival rates, and clinical factors affecting prognosis were examined. RESULTS: The HPV-positive rate in patients with OPC was low, with the lowest rate of 10.0% in 2013 and the highest rate of 46.7% in 2020. The number of HPV-negative cases remained almost unchanged, whereas the overall number of cases increased with the increasing number of HPV-positive cases. Additionally, HPV-positive cases exhibited a fairly good prognosis. CONCLUSION: The number of OPC cases increased not only in urban areas, but also in rural areas. HPV-positive cases had better outcomes than HPV-negative cases.

Electron beam detection in radiotherapy using a capacitor dosimeter equipped with a silicon photodiode.

In this study, a newly developed capacitor dosimeter was evaluated using electron beams commonly utilized in radiotherapy. The capacitor dosimeter comprised a silicon photodiode, 0.47-µF capacitor, and dedicated terminal (dock). Before electron beam irradiation, the dosimeter was charged using the dock. The doses were measured without using a cable by reducing the charging voltages using the currents from the photodiode during irradiation. A commercially available parallel-plane-type ionization chamber and solid-water phantom were used for dose calibration with an electron energy of 6 MeV. In addition, the depth doses were measured using a solid-water phantom at electron energies of 6, 9, and 12 MeV. The doses were proportional to the discharging voltages, and the maximum dose difference in the calibrated doses measured using a two-point calibration was approximately 5% in the range of 0.25-1.98 Gy. The depth dependencies at energies of 6, 9, and 12 MeV corresponded to those measured using the ionization chamber.

Salvage craniospinal irradiation for recurrent intracranial germinoma: a single institution analysis.

This study investigated the effectiveness and safety of low-dose salvage craniospinal irradiation (CSI) for recurrent germinoma. We retrospectively reviewed long-term tumor control and late adverse effects in 15 recurrent germinoma patients treated at our hospital between 1983 and 2019. Following the first recurrence of germinoma, seven were treated with 24-30 Gy of salvage CSI, three underwent non-CSI, and five were treated with only chemotherapy. CSI achieved a significantly better recurrence-free survival rate after the first recurrence compared to other strategies (100% vs 33%, p < 0.001: log-rank test). To evaluate the safety of salvage CSI, we assessed the outcomes at the final follow-up of seven patients who received salvage CSI at first recurrence and three patients who received salvage CSI at second recurrence. The median follow-up period was 220 months after initial treatment. Five patients who received 40-50 Gy of radiation therapy or underwent multiple radiation therapy before salvage CSI were classified into Group A, whereas five patients treated with platinum-based chemotherapy and 24-32 Gy of radiation therapy to the primary site, whole ventricle, or whole brain were classified into Group B. In Group A, one had endocrine dysfunction and the other had visual dysfunction. None were socially independent. Meanwhile, in Group B, no endocrine or visual dysfunction was found, and three patients were socially independent. Salvage CSI achieved excellent tumor control in recurrent germinoma and was safe in patients initially treated with low-dose radiation therapy and chemotherapy.

Durable Response After Combination Therapy With Enfortumab Vedotin and Radiotherapy in Metastatic Urothelial Carcinoma: A Report of Two Cases.

Enfortumab vedotin for urothelial carcinoma is a potentially effective anti-tumor drug that can be used in 3rd-line therapy or later, even in relatively advanced stages of the disease. Here, we present two cases of treatment using enfortumab vedotin with subsequent radiotherapy for primary lesions, and long-term disease control was achieved. The first case involved a 78-year-old man previously treated with pembrolizumab following gemcitabine plus carboplatin for lower ureteral carcinoma with multiple lung and lymph node metastases. Six months after the initiation of enfortumab vedotin, the primary tumor and metastases notably shrank. However, the primary tumor regrew, and radiotherapy was initiated along with enfortumab vedotin. The second case involved a 60-year-old man who was initially treated with avelumab following gemcitabine plus cisplatin for bladder cancer with multiple lymph node metastases. After two months of enfortumab vedotin, the primary and metastatic lesions shrunk. However, the primary tumor regrew, and radiotherapy was initiated. In both cases, the primary tumor and metastases recorded long-term shrinkage. The combination of radiotherapy and enfortumab vedotin may be an effective treatment option.

Treatment Outcomes and Prognostic Factors of Concurrent Chemoradiotherapy With Docetaxel, Cisplatin, and Fluorouracil in Advanced Head and Neck Cancer.

BACKGROUND/AIM: Although the efficacy of docetaxel, cisplatin, and 5-Fluorouracil (TPF) as induction chemotherapy has been confirmed, the therapeutic outcome and prognostic factors of concurrent chemoradiotherapy (CCRT) should be investigated. PATIENTS AND METHODS: Laboratory data of patients who underwent CCRT for advanced squamous cell carcinoma (SCC) of the head and neck were investigated to clarify the grade of side effects. Survival rates and prognostic scores were also calculated. Multivariate analysis was performed to examine the prognostic factors of the patients. RESULTS: Although there were significantly more advanced cases in the TPF group (n=72) than those in the cisplatin group (n=50), there were no significant differences in patient survival rates. In the TPF group, the lymphocyte count, albumin level, and C-reactive protein level of the patients before treatment were significantly correlated with patient outcomes. CONCLUSION: CCRT using the TPF regimen had remarkable treatment effects in advanced head and neck cancer.

Primary rhabdomyosarcoma of the ethmoid sinus with orbital extension and metastasis to the pancreatic body.

This case report highlights the need for clinicians to monitor patients with rhabdomyosarcoma for pancreatic metastasis to ensure that proper treatment is quickly provided, thereby improving outcomes.

Assessment of a computed tomography-based radiomics approach for assessing lung function in lung cancer patients.

PURPOSE: We aimed to assess radiomics approaches for estimating three pulmonary function test (PFT) results (forced expiratory volume in one second [FEV1], forced vital capacity [FVC], and the ratio of FEV1 to FVC [FEV1/FVC]) using data extracted from chest computed tomography (CT) images. METHODS: This retrospective study included 85 lung cancer patients (mean age, 75 years ±8; 69 men) who underwent stereotactic body radiotherapy between 2012 and 2020. Their pretreatment chest breath-hold CT and PFT data before radiotherapy were obtained. A total of 107 radiomics features (Shape: 14, Intensity: 18, Texture: 75) were extracted using two methods: extraction of the lung tissue (<-250 HU) (APPROACH 1), and extraction of small blood vessels and lung tissue (APPROACH 2). The PFT results were estimated using the least absolute shrinkage and selection operator regression. Pearson's correlation coefficients (r) were determined for all PFT results, and the area under the curve (AUC) was calculated for FEV1/FVC (<70 %). Finally, we compared our approaches with the conventional formula (Conventional). RESULTS: For the estimated FEV1/FVC, the Pearson's r were 0.21 (P =.06), 0.69 (P <.01), and 0.73 (P <.01) for Conventional, APPROACH 1, and APPROACH 2, respectively; the AUCs for FEV1/FVC (<70 %) were 0.67 (95 % confidence interval [CI]: 0.55, 0.79), 0.82 (CI: 0.72, 0.91; P =.047) and 0.86 (CI: 0.78, 0.94; P =.01), respectively. CONCLUSIONS: The radiomics approach performed better than the conventional equation and may be useful for assessing lung function based on CT images.

Preliminary Study of Chemoradiotherapy Using Modified Docetaxel, Cis-diaminodichloroplatinum, and 5-Fluorouracil for Sinonasal Squamous Cell Carcinoma.

OBJECTIVE: To examine the safety and efficacy of concomitant chemoradiotherapy using a modified TPF regimen (docetaxel + cisplatin + 5-fluorouracil) in patients with advanced sinonasal squamous cell carcinoma (SNSCC). STUDY DESIGN: Retrospective study. SETTING: Tertiary center (university hospital). METHODS: Seven patients with previously untreated T3-T4 SNSCC were enrolled. They underwent radiotherapy once daily (total dose, 70 Gy) with 2 courses of concomitant 120-hour infusion of 5-fluorouracil (600 mg/m2/d), docetaxel (50 mg/m2, day 2), and cisplatin (60 mg/m2, day 2). RESULTS: Grade 4 leukopenia, grade 4 neutropenia, and grade 3 lymphopenia were observed in 1, 3, and 4 patients, respectively. Grade 4 creatinine elevation was observed in 1 patient. However, other grade 3 or 4 adverse events were not common. Complete response was obtained in all patients. At 60 months there was 85.7% disease-free survival and 100% overall. CONCLUSION: Concomitant chemoradiotherapy with a modified TPF regimen may be feasible and effective in patients with advanced SNSCC.

Development of a dose-rate dosimeter for x-ray CT scanner using silicon x-ray diode.

In an x-ray diagnosis, it is important to evaluate the entrance dose rate, as the dose rate of exposure becomes highest in that position. To investigate the effect of the entrance dose rate of x-ray CT scanners, a dose-rate dosimeter comprising a silicon x-ray diode (Si-XD), a CMOS dual operational amplifier, resistors, capacitors, and a mini-substrate measuring 20 × 17 mm2 were developed. The Si-XD is desirable for measuring the changing entrance dose rate, as it enables the reduction of the response time, dimensions, and cost of the dosimeter. The dosimeter was connected to a microcomputer (mbed), and the output voltages from the dosimeter were measured using an analog-digital converter in the mbed. The output voltages were proportional to the tube currents at a constant tube voltage of 100 kV using an industrial x-ray tube, and the calibrated dose rates corresponded well to those obtained using a commercially available semiconductor dosimeter. However, owing to the energy dependence of the dosimeter, the calibrated dose rate was ∼10% higher than that of a commercially available semiconductor dosimeter at the lower tube voltage. In the angular dependence of the dosimeter, the flatness measured from 60° to 120° was ∼103% in this study. A fundamental study for measuring the dose-rate variations with rotation was performed. The results showed a different profile than the angular dependence due to the distance from the source and the complex factors of the scattered radiation.

Characterization of an under-development capacitor dosimeter equipped with a silicon x-ray diode.

Herein, we evaluated a capacitor dosimeter under development by a manufacturer, which is designed to monitor the entrance dose in x-ray diagnosis and comprises a silicon x-ray diode (Si-XD), a 0.1 µF capacitor, and a dosimeter dock. The Si-XD is a high-sensitivity photodiode optimized for x-ray detection. The dosimeter was charged to 3.30 V using the dock before x-ray irradiation. The charging voltage was reduced by photocurrents flowing through the Si-XD during irradiation, and the discharging voltage was measured. For the fundamental characterization of this capacitor dosimeter, we investigated the x-ray tube-current and tube-voltage dependences of the measured dose using an industrial x-ray tube; the angular dependence was also investigated. A commercially available semiconductor dosimeter (RaySafe ThinX) was used for dose calibration. The doses were proportional to the tube current at a constant tube voltage of 100 kV and increased with increasing tube voltage at a constant tube current of 1.0 mA. The dose difference with respect to the commercially available semiconductor dosimeter was within 1.0% when the tube current was varied and it was within 3.0% when the tube voltage was varied. In the angular dependence measurement, a difference of up to 6.0% was observed as the angle varied from 0° to 355° in steps of 5°. The dose-calibration results indicated that the determination of the initial charging voltage was important for dose conversion using the capacitor dosimeter.

Stereotactic body radiotherapy with a single isocentre for multiple pulmonary metastases.

A 45-year-old male developed a second set of pulmonary metastases 5 years after surgery for extraskeletal mucinous chondrosarcoma of the left shoulder. He already underwent a lobectomy and two segmentectomies for a first set of pulmonary metastases 2 years ago. The closely grouped three nodules within the left lower lung formed a planning target volume (PTV) for stereotactic body radiotherapy (SBRT) with a single isocentre, which was focused on the centre of the largest nodule (the simultaneous plan). Dose-volume histogram analysis confirmed that the plan was superior to an alternative plan, in which SBRT plans would have been produced for each individual tumour (the individual plan). The mean, maximum and minimum PTV doses were 54.0, 57.5 and 47.3 Gy, respectively, in the simultaneous plan, and 65.6, 87.2 and 52.3 Gy, respectively, in the individual plan. The homogeneity index, conformity index, and the maximum dose delivered to the surrounding healthy lung were 1.21, 0.71, and 37.7 Gy, respectively, in the simultaneous plan and 1.66, 4.44, and 46.2 Gy, respectively, in the individual plan. The patient developed Grade two pneumonitis, but remained healthy until 4 years after the SBRT. When multiple closely grouped metastases are treated using SBRT, the use of a single isocentre should be considered.

Modified Glasgow prognostic score can predict survival of muscle invasive bladder cancer patients after radiotherapy.

In patients with various cancers, modified Glasgow prognostic score (mGPS) before treatment has predicted prognoses after antitumor therapy. This study aimed to assess whether pretreatment mGPS also has predictive value in patients with muscle-invasive bladder cancer (MIBC) after radiotherapy. A retrospective review accumulated 98 consecutive MIBC patients treated with definitive 3D-conformal radiotherapy from January 2011 to December 2016 in a single center. It included cT2-4bN0-3M0 patients with a median age of 79 years (range: 49 to 95 years). Radiotherapy was delivered at 60-66 Gy for bladder cancer. Patients were categorized in terms of their pretreatment serum albumin and C-reactive protein (CRP) values as mGPS_0, mGPS_1, and mGPS_2. Among them, cumulative overall survival (OS) rates were compared by Kaplan-Meier plots with log-rank tests. The number of patients with mGPS_0, mGPS_1, and mGPS_2 were 40, 40, and 18, respectively. The median follow-up time for all patients was 19 months (range: 2-73 months). The 2-year OS rate for all patients was 75.7%. The 2-year OS rates for mGPS_0, mGPS_1, and mGPS_2 were 85.1%, 71.3%, and 60.9%, respectively. Kaplan-Meier curves revealed a significantly higher cumulative OS rate for mGPS_0 compared with mGPS_1 and mGPS_2 (P = 0.003). Using multivariate Cox regression analysis, mGPS_0 and good performance status were associated with favorable OS rates, of which mGPS_0 was more significant (Hazard ratio 2.74, 95% CI 1.30-5.57, P = 0.008). Modified Glasgow prognostic score may be a novel biomarker that can predict survival in patients with MIBC after radiotherapy.

Long-Term Outcomes of Patients with Squamous Cell Carcinoma of the Temporal Bone after Concomitant Chemoradiotherapy.

Objectives This article aims to clarify the long-term outcomes of patients with squamous cell carcinoma of the temporal bone who underwent concomitant chemoradiotherapy (CCRT). Design and Setting The study design was a retrospective chart review. Patients and Methods From December 2001 to June 2014, 23 patients with cancer of the temporal bone who were treated by CCRT at the Tohoku University Hospital and the Iwate Medical University Hospital were enrolled in this study. For advanced cancer of the temporal bone, a modified docetaxel, cisplatin, and 5-fluorouracil (TPF) regimen was used for CCRT. The long-term outcomes, including prognoses and late complications, were analyzed after CCRT of patients with cancers of the temporal bone. Results The main long-term complications were stenosis of the external auditory canal and conductive hearing loss. No harmful late complications were observed in these patients. Disease-specific survival rates were 84.9% for all patients, 100% for patients of stage I, II, and III ( n = 10), and 75.5% for patients of stage IV ( n = 13) at 5 years. Conclusions Our study showed that CCRT is an effective treatment choice for squamous cell carcinoma of the temporal bone. Furthermore, CCRT using the TPF regimen is a safe and effective initial treatment for patients with advanced cancers of the temporal bone.

Partial Bladder Boost Using Lipiodol Marking During Image-guided Radiotherapy for Bladder Cancer.

BACKGROUND/AIM: Secure dose escalation is required to compensate avoidance of concurrent chemotherapy in radiotherapy for increasing elderly bladder cancer. We aimed to evaluate the efficacy of lipiodol submucosally injected as a fiducial marker during image-guided radiotherapy (Lip-IGRT) for muscle invasive bladder cancer (BC). PATIENTS AND METHODS: Twenty-three patients with T2a-4aN0-1M0 BC underwent whole-bladder irradiation of 46 Gy and Lip-IGRT of 20 Gy, conventionally. The bladder volume exposed to 19 Gy (bV19:%) on Lip-IGRT was referred as an index predicting cystitis. RESULTS: Lipiodol consistently highlighted the boundaries of 20 tumors (88%) on planning and portal verification images. Three of 4 patients under oral anticoagulant agents usage were complicated with grade ≥2 hematuria for 3 days (a patient with a bV19 of >50%) or more than a year (2 patients with bV19 of <50%) after the injection. The 3-year overall survival and disease-free survival rates were 70.4% and 71.1%, respectively. CONCLUSION: Lipiodol marking is an effective way of demarcating BC. However, it is necessary to address the comorbidities of elderly patients.

Long-term results of chemoradiotherapy for stage II-III thoracic esophageal cancer in a single institution after 2000 -with a focus on comparison of three protocols.

BACKGROUND: To evaluate the long-term results of chemoradiotherapy (CRT) for stage II-III thoracic esophageal cancer mainly by comparing results of three protocols retrospectively. METHODS: Between 2000 and 2012, 298 patients with stage II-III thoracic esophageal cancer underwent CRT. Patients in Group A received two cycles of cisplatin (CDDP) at 70 mg/m(2) (day 1 and 29) and 5-fluorouracil (5-FU) at 700 mg/m(2)/24 h (day 1-4 and 29-32) with radiotherapy (RT) of 60 Gy without a break. Patients in Group B received two cycles of CDDP at 40 mg/m(2) (day 1, 8, 36 and 43) and 5-FU at 400 mg/m(2)/24 h (day 1-5, 8-12, 36-40 and 43-47) with RT of 60 Gy with a 2-week break. Patients in Group C received two cycles of nedaplatin at 70 mg/m(2) (day 1 and 29) and 5-FU at 500 mg/m(2)/24 h (day 1-4 and 29-32) with RT of 60-70 Gy without a break. Differences in prognostic factors between the groups were analyzed by univariate and multivariate analyses. RESULTS: The 5-year overall survival rates for patients in Group A, Group B and Group C were 52.4, 45.2 and 37.2%, respectively. The 5-year overall survival rates for patients in Stage II, Stage III (non-T4) and Stage III (T4) were 64.0, 40.1 and 22.5%, respectively. The 5-year overall survival rates for patients who received 1 cycle and 2 cycles of concomitant chemotherapy were 27.9 and 46.0%, respectively. In univariate analysis, stage, performance status and number of concomitant chemotherapy cycles were significant prognostic factors (p < 0.001, p = 0.008 and p < 0.001, respectively). In multivariate analysis, stage, protocol and number of concomitant chemotherapy cycles were significant factors (p < 0.001, p = 0.043 and p < 0.001, respectively). CONCLUSIONS: The protocol used in Group A may be an effective protocol of CRT for esophageal cancer. It may be important to complete the scheduled concomitant chemotherapy with the appropriate intensity of CRT.

Measurement of X-ray spectra using a Lu2(SiO4)O-multipixel-photon detector with changes in the pixel number.

To measure X-ray spectra with high count rates, we developed a detector consisting of a Lu2(SiO4)O [LSO] crystal with a decay time of 40 ns and a multipixel photon counter (MPPC). The photocurrents flowing through the MPPC are converted into voltages and amplified by a high-speed current-voltage amplifier, and event pulses from the amplifier are sent to a multichannel analyzer to measure spectra. We used three MPPCs of 100, 400 and 1600 pixels/mm(2), and the MPPCs were driven under pre-Geiger mode at a temperature of 20 °C. At a tube voltage of 100 kV and a tube current of 5.0 µA, the maximum count rate was 12.8 kilo-counts per second. The event-pulse widths were 200 ns, and the energy resolution was 53% at 59.5 keV using a 100-pixel MPPC.

Investigation of the clinicopathological features of squamous cell carcinoma of the vulva: a retrospective survey of the Tohoku Gynecologic Cancer Unit.

BACKGROUND: This multi-institutional study was conducted to clarify the clinicopathological features of squamous cell carcinomas of the vulva. METHODS: The medical records of vulvar cancer patients treated between 2002 and 2012 were retrospectively reviewed following approval by the Institutional Review Board of each institution. RESULTS: One hundred and eleven patients with vulvar malignancies were included. Of these, 63 patients had squamous cell carcinoma (57 %). Initial treatment was surgery, radiation therapy (RT), and concurrent chemoradiotherapy (CCRT) in 34 (54 %), 15 (24 %), and 11 (17 %) patients, respectively. Nineteen, 11, 26, and 7 patients had stage I, II, III, and IV disease, respectively. Of the 34 patients who had surgical treatment, 50 % had stage I disease, while 74 % of those who received CCRT had stage III or IV disease. Complete response (CR) rates for the surgery, RT, and CCRT groups were 73, 60, and 64 %, respectively. The 5-year survival rates for stage I/II and III/IV disease were 64 and 39 %, respectively (P = 0.019). The 5-year survival rates for the surgery, RT, and CCRT groups were 53, 38, and 50 %, respectively, and the prognosis of patients treated with surgery or CCRT was significantly better than that of patients who received RT (P < 0.05). In multivariate analysis, clinical response to initial treatment was an independent prognostic factor (P < 0.001). CONCLUSIONS: Although many patients had advanced-stage disease in the CCRT group, the therapeutic outcome for the surgery and CCRT groups was similar. Thus, CCRT may be a promising treatment for squamous cell carcinoma of the vulva.

Three-dimensional summation of rectal doses in brachytherapy combined with external beam radiotherapy for prostate cancer.

BACKGROUND AND PURPOSE: To determine the dose constraints for rectal bleeding in brachytherapy (BRT) combined with external beam radiotherapy (EBRT). MATERIALS AND METHODS: Post-BRT, pelvic computed tomography images were used for subsequent EBRT planning and BRT postplans in 37 patients. The physical doses for each plan were converted to biologically effective doses, and corresponding voxel doses were integrated to plot the summed dose-volume histogram (sum-DVH). Between 5 patients with (bled-pts) and 32 without (spared-pts) grade 2 or 3 rectal bleeding, the differences in the mean minimal dose (rDn) covering the rectal volume of 0.5-10.0 cc and the rectal volume (rVn) receiving the calculated dose of 20-150Gy were compared. RESULTS: The differences in the summed-rDn were determined by BRT exposure, while those of the summed-rVn were determined in the low-dose range and superimposed in the high-dose range by EBRT exposure. Of the 13 patients with rV150 of >1.2 cc, 4 were bled-pts (30.8%). Of the 24 patients with rV150 of ≤ 1.2cc, 1 was a bled-pts (4.2%) (p=0.024; odds ratio, 10.2; CI (95%), 1.0-104.3). CONCLUSIONS: The mono-scale DVH analysis is a promising method for exploring the threshold for rectal bleeding in combined radiotherapy.