International Commission On Radiation Units And Measurements Bladder Research Articles

Evaluation of variation of interfraction doses to organs at risk during brachytherapy of cervical cancer

BackgroundTwo-dimensional treatment planning using radiographs or simulator films was the standard in planning brachytherapy for patients with cervical cancer. Three-dimensional (3D) treatment planning has improved treatment efficacy. This retrospective study compares conventional and 3D treatment planning of brachytherapy in patients with cervical cancer and interfraction dose variation to bladder and rectum (D2cc). MethodsThe mean doses to bladder and rectum (D2cc) were computed by computed tomography (CT)–based planning during 100 sessions of intracavitary brachytherapy for carcinoma cervix with the same source configuration as generated for conventional planning, and these estimates were compared with the doses at International Commission on Radiation Units and measurements (ICRU) rectal, bladder points and point A. Interfraction variation of doses to bladder and rectum during various sessions was also analysed. ResultThe mean ICRU bladder dose and D2cc of the bladder for all patients was 3.7 Gy and 7.4 Gy, respectively (p < 0.001). The mean ICRU rectal dose from conventional plan was 4.3Gy and with CT planning, 4.45 Gy (p = 0.04). Interfraction dose variations for D2cc of the bladder were min −5.3 Gy and max 4.8 Gy and those of the rectum were min −1.8 Gy and max 1.72Gy. ConclusionDosimetric evaluation of conventional and 3D CT-based treatment planning for the same brachytherapy sessions demonstrated underestimation of ICRU bladder dose points (p < 0.001) and the rectal ICRU point dose and D2cc (p=0.04). The doses to organs at risk did not show a statistically significant variation between the fractions. However, large variation was noted between the interfractional maximum and minimum doses to bladder and rectum.

Comparison between DVH-based doses and ICRU point-based doses to the rectum and the bladder using CT-based high-dose rate brachytherapy to the cervix

Traditionally, doses to the bladder and the rectum were quantified using the bladder and rectal reference points defined by the International Commission on Radiation Units and Measurements (ICRU) in Report No. 38. In this study, we compared the 0.1-, 1.0-, 2.0-cc doses to the bladder and the rectum with the corresponding ICRU point doses using computed tomography (CT)-based planning in the intracavitary brachytherapy of carcinoma of the cervix. CT datasets of 136 consecutive intracavitary brachytherapy insertions between January and May 2015 were analyzed. The bladder and the rectum were contoured on consecutive CT slices as per Groupe Europeen de Curietherapie and the European Socie Ty for Radiotherapy and Oncology recommendations. Dose volume histograms were generated and doses of 0.1, 1.0, and 2.0 cc to the bladder and the rectum were recorded. ICRU bladder and rectal points were identified in the treatment plan. Mean doses of 0.1, 1.0, and 2.0 cc to the bladder was found to be 2.02, 1.57, and 1.35 times the ICRU point dose, respectively. The maximum dose received by the bladder was found to be 5.83 times the average ICRU point dose. Mean doses of 0.1, 1.0, and 2.0 cc to the rectum were found to be 1.12, 0.90, and 0.78 times the ICRU rectal point dose, respectively. The maximum dose received by the rectum was 4.79 times the average ICRU point dose. The Pearson correlation coefficient value (r) was found to be 0.639 for D2cc and ICRU bladder point values. The Pearson correlation coefficient value was found to be 0.752 for D2cc and ICRU rectal point values. Our results show that the ICRU bladder points underestimated the dose to the bladder, which is in agreement with other studies. ICRU rectal point doses were higher than the corresponding D2cc doses. However, there was a good correlation between D2cc and ICRU point doses for both the bladder and the rectum.

De-escalation of the cumulative central radiation dose according to the tumor response can reduce rectal toxicity without compromising the treatment outcome in patients with uterine cervical cancer

ObjectiveTo assess the treatment outcome and toxicity of a low cumulative central dose using a midline block (MLB) during external beam radiotherapy (EBRT). MethodsBetween January 1988 and December 2010, 1559 patients with FIGO stage IB–IIB uterine cervical cancer that underwent EBRT and high-dose-rate intracavitary brachytherapy (HDR-ICBT) were retrospectively analyzed. During EBRT, MLB was performed (n=1195, MLB group) when a sufficient response was achieved to insert the tandem through the cervical canal and place ovoids in the vaginal cavity. MLB was not applied for patients with a slow tumor response (n=364, non-MLB group). The doses were estimated according to the International Commission on Radiation Units and Measurements (ICRU) points. The biologically equivalent dose in 2-Gy fractions (EQD2) was calculated to estimate the cumulative dose from EBRT and ICBT. ResultsEQD2pointA, EQD2rectum, and EQD2bladder were all significantly lower in the MLB group (all P<0.05). The 10-year grade≥2 late rectal toxicity rate was significantly lower in the MLB group (P=0.012), while there was no significant difference in late genitourinary and small bowel toxicity. ICRU rectal and bladder doses showed significant predictability on late rectal and bladder toxicities. After propensity score matching, all patient and tumor characteristics were well matched and the survival and recurrence rates between the two groups were similar (all P>0.05), despite the lower EQD2pointA in the MLB group (P<0.001). ConclusionsApplying MLB according to tumor response during EBRT lowered the cumulative central dose and reduced late rectal toxicity without compromising treatment outcome.

English

Conventional two-dimensional (2D) treatment planning of intracavitary brachytherapy is still a common practice at the radiotherapy center. The purpose of this study was to evaluate the organ at risk (OAR) doses estimated based on International Commission on Radiation Units and Measurements (ICRU) reference-point in patients with cervical cancer treated with high-dose-rate (HDR) intracavitary brachytherapy (ICBT). Between January 2010 and April 2014, 21 cervical cancer patients were treated with 42 fractions of brachytherapy using tandem and ovoids and underwent post-implant two-dimensional (2D) radiograph scans. HDR brachytherapy was delivered to a dose of 18 Gy in two fractions. Using the Oncentra brachytherapy treatment planning system (BTPS) software version 4.1 (Nucletron, Netherlands), the bladder and rectum points were retrospectively reconstructed based on 42 orthogonal radiographs datasets. The ICRU bladder and rectum point doses were recorded. As for results, the mean percentage dose of rectum and bladder for selected patients treated with intracavitary brachytherapy treatment (ICBT) were 47.27 and 75.59%, respectively. Combinations of ovoid’s size, length of tandem and anatomy variation between each patient were factors that affected the dose to the OAR. Therefore, the ICRU reference points can still be used with the 2D brachytherapy treatment planning in evaluating the OAR doses.

Volumetric evaluation of an alternative bladder point in brachytherapy for locally advanced cervical cancer

To evaluate an alternative dose point, so-called ALG (for Alain Gerbaulet), for the bladder in comparison to the International Commission on Radiation Units and Measurements (ICRU) point and D2cm(3) (minimal dose to maximally exposed 2 cm(3)) in a large cohort of patients with locally advanced cervical cancer treated with external beam radiotherapy followed by image-guided pulsed dose rate brachytherapy. For each patient, the ALG point was constructed 1.5 cm above the ICRU bladder, parallel to the tandem (coronal and sagittal planes). The dosimetric data from 162 patients were reviewed. Average doses to ALG and bladder points were 19.40 Gy ± 7.93 and 17.14 ± 8.70, respectively (p=0.01). The 2 cm(3) bladder dose averaged 24.40 ± 6.77 Gy. Ratios between D2cm(3) and dose points were 1.37 ± 0.46 and 1.68 ± 0.74 (p<0.001) for ALG and ICRU points, respectively. Both dose points appeared correlated with D2cm(3) (p<0.001) with coefficients of determination (R(2)) of 0.331 and 0.399 respectively. The estimated dose to the ICRU point of the rectum was 12.77 ± 4.21 and 15.76 ± 5.94 for D2cm(3) (p<0.0001). Both values were significantly correlated (p<0.0001, R(2) = 0.485). The ALG point underestimates the D2cm(3), but its mean on a large cohort is closer to D2cm(3) than the dose to ICRU point. However, it shows great variability between cases and the weak strength of its correlation to D2cm(3) indicates that it is not a good surrogate for individual volumetric evaluation of the dose D2cm(3).

Evaluation of a balloon-based vaginal packing system and patient-controlled analgesia for patients with cervical cancer undergoing high-dose-rate intracavitary brachytherapy

PurposeTo evaluate the following: (1) the dosimetric impact on the bladder and rectum due to a methodologic shift from general anesthesia (GA) to patient-controlled analgesia (PCA), and from vaginal gauze packing (VGP) to vaginal balloon-based packing (VBP) for high-dose-rate (HDR) intracavitary brachytherapy; and (2) the tolerability of PCA versus GA. Methods and MaterialsSeventeen consecutively treated patients with cervical carcinoma who underwent tandem and ovoid (T&O) HDR brachytherapy from January 2009 to August 2010 were selected and reviewed. There were a total of 73 applications. Patients were packed either conventionally with VGP (n = 49) or with VBP (n = 24). Because different sedation methods can influence rectal and bladder dosimetric parameters all applications were grouped by packing method (VBP or VGP) as well as sedation method (GA or PCA). The International Commission on Radiation Units and Measurements (ICRU) and D2cc rectal and bladder doses were obtained from the treatment records and dose-volume histograms, and respective percentage of prescription dose noted and compared. For patients receiving PCA, pain score on a scale of 0-10 was noted. ResultsAll patients who used PCA were able to tolerate and complete the procedure with a median pain score of 0 (range, 0-2). Implants packed with the VBP method under PCA (n = 21) versus VGP under GA (n = 40) had significantly lower doses to the bladder D2cc (85.7% vs 104.8% of prescription dose), and rectum ICRU dose point (55.4% vs 65.2% of prescription dose), P = .0371 and .039, respectively. The ICRU bladder point and rectum D2cc between the 2 groups were not significantly different. ConclusionsOur results demonstrate that PCA is a feasible method for pain control for T&O brachytherapy. VBP and PCA are compatible with T&O brachytherapy and resulted in comparable if not better bladder and rectal dosimetry.

Impact of Heterogeneity-Based Dose Calculation Using a Deterministic Grid-Based Boltzmann Equation Solver for Intracavitary Brachytherapy

To investigate the dosimetric impact of the heterogeneity dose calculation Acuros (Transpire Inc., Gig Harbor, WA), a grid-based Boltzmann equation solver (GBBS), for brachytherapy in a cohort of cervical cancer patients. The impact of heterogeneities was retrospectively assessed in treatment plans for 26 patients who had previously received (192)Ir intracavitary brachytherapy for cervical cancer with computed tomography (CT)/magnetic resonance-compatible tandems and unshielded colpostats. The GBBS models sources, patient boundaries, applicators, and tissue heterogeneities. Multiple GBBS calculations were performed with and without solid model applicator, with and without overriding the patient contour to 1 g/cm(3) muscle, and with and without overriding contrast materials to muscle or 2.25 g/cm(3) bone. Impact of source and boundary modeling, applicator, tissue heterogeneities, and sensitivity of CT-to-material mapping of contrast were derived from the multiple calculations. American Association of Physicists in Medicine Task Group 43 (TG-43) guidelines and the GBBS were compared for the following clinical dosimetric parameters: Manchester points A and B, International Commission on Radiation Units and Measurements (ICRU) report 38 rectal and bladder points, three and nine o'clock, and (D2cm3) to the bladder, rectum, and sigmoid. Points A and B, D(2) cm(3) bladder, ICRU bladder, and three and nine o'clock were within 5% of TG-43 for all GBBS calculations. The source and boundary and applicator account for most of the differences between the GBBS and TG-43 guidelines. The D(2cm3) rectum (n = 3), D(2cm3) sigmoid (n = 1), and ICRU rectum (n = 6) had differences of >5% from TG-43 for the worst case incorrect mapping of contrast to bone. Clinical dosimetric parameters were within 5% of TG-43 when rectal and balloon contrast were mapped to bone and radiopaque packing was not overridden. The GBBS has minimal impact on clinical parameters for this cohort of patients with unshielded applicators. The incorrect mapping of rectal and balloon contrast does not have a significant impact on clinical parameters. Rectal parameters may be sensitive to the mapping of radiopaque packing.

The dosimetric impact of heterogeneity corrections in high-dose-rate 192Ir brachytherapy for cervical cancer: Investigation of both conventional Point-A and volume-optimized plans

PurposeTo evaluate the dosimetric impact of heterogeneity corrections on both conventional and volume-optimized high-dose-rate (HDR) 192Ir brachytherapy tandem-and-ovoid treatment plans. Methods and MaterialsBoth conventional and volume-optimized treatment plans were retrospectively created using eight unique CT data sets. In the volume-optimized plans, the clinical target volume (CTV) and organs-at-risk (rectum, bladder, and sigmoid) were contoured on the CT data sets by a single physician. For each plan, dose calculations representing homogeneous water medium were performed using the Task Group (TG-43) formalism and dose calculations with heterogeneity corrections were performed using a commercially available treatment planning system. ResultsFor the conventional plans, the change in dose between TG-43 and heterogeneity-corrected calculations was assessed for the following points: Point-A (left and right) and International Commission on Radiation Units and Measurements (ICRU) 38 defined rectum and bladder points. It was found that the dose to the ICRU bladder decreased the most (−2.2±0.9%), whereas ICRU rectum (−1.7±0.8%), Point-A right (−1.1±0.4%), and Point-A left (−1.0±0.3%) also showed decreases with heterogeneity-corrected calculations. For the volume-optimized plans, the change in dose between TG-43 and heterogeneity-corrected calculations was assessed for the following dose–volume histogram parameters: D90 of the CTV and D2cc of the rectum, bladder, and sigmoid. It was found that D90 of the CTV decreased by −1.9±0.7% and D2cc decreased by −2.6±1.4%, −1.0±0.4%, and −2.0±0.6% for the rectum, bladder and sigmoid, respectively, with heterogeneity-corrected calculations. ConclusionsHeterogeneity corrections on high-dose rate plans were found to have only a small dosimetric impact over TG-43-based dose calculations for both conventional Point-A and volume-optimized plans.

Non isocentric film-based intracavitary brachytherapy planning in cervical cancer: a retrospective dosimetric analysis with CT planning.

PurposeTo compare intracavitary brachytherapy dose estimation for organs at risk (bladder and rectum) based on semi-orthogonal reconstruction of radiographs on non-isocentric X-ray unit and Computed Tomography (CT) – based volumetric planning in cervical cancer.Material and methodsBladder and rectal points as per International Commission on Radiation Units and Measurements (ICRU) report 38, were retrospectively evaluated on 15 high dose rate intracavitary brachytherapy applications for cervical cancer cases. With the same source configuration as obtained during planning on radiographs performed on a non-isocentric X-ray unit, the mean doses to 2cc of most irradiated part of bladder and rectum were computed by CT planning and these estimates were compared with the doses at ICRU bladder and rectal points.ResultsThe mean ICRU point dose for bladder was 3.08 Gy (1.9-5.9 Gy) and mean dose to 2 cc (D2cc) bladder was 6.91 Gy (2.9-12.2 Gy). ICRU rectal dose was 3.8 Gy (2.4-4.45 Gy) and was comparable with D2cc rectum dose 4.2 Gy (2.8-5.9 Gy). Comparison of mean total dose (ICRU point vs. D2cc) for each patient was found to be significantly different for bladder (p = 0.000), but not for rectum (p = 0.08).ConclusionsOn comparison of ICRU point based planning with volumetric planning on CT, it was found that bladder doses were underestimated by the film based method. However, the rectal doses were found to be similar to the D2cc doses. The results with non isocentric film based treatment planning were similar to the existing literature on orthogonal film based simulator planning.

2D to 3D Evaluation of Organs at Risk Doses in Intracavitary Brachytherapy for Cervical Cancer.

PurposeTo compare International Commission on Radiation Units and Measurements (ICRU) bladder and rectum reference points doses with volumetric doses in 3D intracavitary brachytherapy (ICBT) for cervical cancer. Also to compare bladder, rectum and sigmoid (organs at risk, OARs) volume doses with dose constraints recommended by the (GYN) GEC-ESTRO Working Group.Material and methodsA retrospective study was carried out on 10 patients with a total of 55 fractions CT-based high dose rate (HDR) ICBT. ICRU bladder (bICRU) and rectum (rICRU) points were defined according to ICRU Report 38 on the CT images and prospectively kept to less than 80% of prescription dose to Point A during real treatment planning. Post-treatment, outer wall of OARs were contoured and minimum dose to 2cc (D2cc) of the most irradiated part of the OARs was obtained from the dose-volume histogram (DVH). Total dose (external beam radiotherapy plus ICBT) were computed with ICRU point dose and D2cc and compared.ResultsThe mean ICRU point dose and D2cc volume dose were found to be significantly different for bladder (per fraction: p = 0.000; total dose: p = 0.004) but no differences were found for rectum (per fraction: p = 0.055; total dose: p = 0.090). bICRU point dose underestimated D2cc dose with an average ratio of 1.34 ± 0.34. 3 out of 10 patients, 7 out of 10 patients, and 5 out of 10 patients exceeded the recommended dose constraint for bladder, rectum, and sigmoid, respectively.ConclusionsbICRU was not representative of bladder D2cc and resulted in different total dose. rICRU was found to be similar to D2cc dose and was reliable in total dose computation. Our current institutional practice of point-based planning in ICBT resulted in significant number of patients’ OARs doses exceeded the volume constraint, because the total dose concept was not used propectively in planning.

Effect of bladder distention on bladder base dose in gynaecological intracavitary high dose rate brachytherapy

The purpose of this study was to assess the impact of bladder volume on bladder base doses during gynaecological intracavitary high dose rate (HDR) brachytherapy. 42 different intracavitary HDR brachytherapy applications (tandem and ovoid, 25; ovoid, 17) were performed in 41 patients treated for cervical (n = 29) and endometrial (n = 12) cancer. The International Commission on Radiation Units and Measurements (ICRU) bladder reference point (BRP) dose and doses of 17 points selected on the bladder base were calculated using planning orthogonal radiographs taken after applicator placement with 100 ml and 270 ml bladder volumes. The effect of bladder volume on ICRU BRP and bladder base maximum point (BBMP) doses were analysed for both types of applications. Median ICRU BRP doses (in percentage of prescription dose) were 36.2% (18.2-69.8%) and 40.0% (21.0-61.8%) for ovoid applications (p = 0.13) and 34.9% (15.7-81.0%) and 33.8% (16.5-88.1%) for tandem and ovoid applications (p = 0.48) in 100 ml and 270 ml bladder volumes, respectively. Median BBMP doses were 75.1% (33.8-141.0%) and 104.0% (62.8-223.0%) for ovoid applications (p<0.001) and 116% (51.2-242.0%) and 124.0% (62.0-326%) for tandem and ovoid applications (p = 0.018) in 100 ml and 270 ml bladder volumes, respectively. Although the BBMP dose significantly increases, the ICRU BRP dose does not change with increasing bladder volume in gynaecological intracavitary HDR brachytherapy. Increasing bladder volume increases bladder base maximum dose in intracavitary gynaecological brachytherapy.

Point vs. volumetric bladder and rectal doses in combined intracavitary-interstitial high-dose-rate brachytherapy: Correlation and comparison with published Vienna applicator data

Purpose We correlated rectal and bladder point and volumetric dose data in patients treated for advanced cervix cancers with combined intracavitary-interstitial high-dose-rate (HDR) brachytherapy (BT). The results are compared with published Vienna applicator data. Methods and Materials We retrospectively analyzed 30 individual combined intracavitary plus interstitial implants from 10 patients treated with external beam radiation therapy (EBRT) followed by HDR BT for locally advanced cervix carcinoma. EBRT consisted of 45 Gy to the pelvis followed by 9–14.4 Gy boost to involved parametria. BT consisted of a total dose of 21 Gy delivered in 7 Gy fraction. For each implant, CT-image-based simulation and image-guided BT treatment planning was performed. Bladder and rectal doses were evaluated and analyzed using both International commission on Radiation Units and Measurements (ICRU) reference points and dose–volume histograms. The cumulative doses to the rectum and bladder were calculated by combining contributions from external beam therapy and BT. To facilitate comparison with published literature, the total doses were normalized to equivalent dose in 2-Gy fractions (EQD 2) using the equation EQD 2total = EQD 2EBRT + EQD 2BT. Results For the patient population considered, the mean ICRU bladder dose was 75 (±4) Gy 3 compared to bladder D 0.1 cc and D 2 cc doses of 84 (±4) and 78 (±3) Gy 3, respectively. The mean ICRU rectal dose was 73 (±4) Gy 3 compared to rectal D 0.1 cc and D 2 cc doses of 79 (±5) and 74 (±4) Gy 3, respectively. For rectum, the mean dose ratios ( D 0.1 cc/ D ICRU) and ( D 2 cc/ D ICRU) were 1.08 and 1.01, respectively, compared to Vienna applicator study mean dose ratios of 1.08 and 0.93, respectively. ICRU rectal dose correlated with volumetric rectal doses and best with volumetric D 2 cc dose ( r S = 0.91, p = 0.0003); however, ICRU bladder dose did not correlate with volumetric bladder dose. Conclusions Our study findings reveal a strong correlation between ICRU rectal reference dose and volumetric rectal D 2 cc dose in combined intracavitary-interstitial HDR brachytherapy. This surrogate rectal–dose relationship is valuable in establishing rectal tolerance dose levels in transitioning from traditional two-dimensional to image-based three-dimensional dose planning.

Image-based three-dimensional treatment planning of intracavitary brachytherapy for cancer of the cervix: Dose-volume histograms of the bladder, rectum, sigmoid colon, and small bowel

Purpose The purpose of this study was to evaluate dose-volume histograms (DVHs) of bladder, rectum, sigmoid colon, and small bowel using image-based three-dimensional treatment planning for intracavitary brachytherapy. Methods and materials Between 2001 and 2003, 22 patients with cancer of the cervix (1 IB1, 5 IB2, 11 IIB, 5 IIIB) were treated with computerized tomography (CT)-compatible high-dose-rate intracavitary applicators and underwent postimplant pelvic CT scans with the applicator in place. The volumes of organs at risk were digitized. For radiography-based planning, International Commission on Radiation Units and Measurements (ICRU) bladder and rectum point doses were calculated. For the CT-based planning, the DVHs were computed for the bladder, rectum, sigmoid colon, and small bowel. To compare doses to organs at risk, the minimum dose in 2.0 cm 3 volume receiving the highest dose ( D 2) was determined from DVHs. These D 2 doses were compared with radiography-based ICRU point doses. Results The mean ICRU bladder point dose (401 cGy) was markedly underestimated compared to the mean bladder D 2 dose (484 cGy). However, the mean ICRU rectal point dose (412 cGy) did not differ significantly from the mean rectal D 2 dose (373 cGy). The most frequent organ receiving the highest D 2 dose was the sigmoid colon in 9 of 22 patients (41%) followed by the rectum in 7 of 22 patients (32%) and small bowel in 6 of 22 patients (27%). Conclusions From CT-based three-dimensional (3-D) evaluation, the ICRU bladder point dose was substantially lower than bladder D 2 dose. Special attention should also be given to the areas of proximal rectum and sigmoid colon due to more frequent high D 2 dose in these areas.

1054: Comparison of Megavoltage CT Image-Based Volumetric Dose Calculations With ICRU Reference Point Estimates of Bladder and Rectal Doses During Low Doserate Intracavitary Brachytherapy for Cervical Cancer

1054: Comparison of Megavoltage CT Image-Based Volumetric Dose Calculations With ICRU Reference Point Estimates of Bladder and Rectal Doses During Low Doserate Intracavitary Brachytherapy for Cervical Cancer

Comparison between CT-based volumetric calculations and ICRU reference-point estimates of radiation doses delivered to bladder and rectum during intracavitary radiotherapy for cervical cancer

To compare CT-based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the uterine cervix treated with definitive low-dose-rate intracavitary radiotherapy (ICRT). Between November 2001 and March 2003, 60 patients were prospectively enrolled in a pilot study of ICRT with CT-based dosimetry. Most patients underwent two ICRT insertions. After insertion of an afterloading ICRT applicator, intraoperative orthogonal films were obtained to ensure proper positioning of the system and to facilitate subsequent planning. Treatments were prescribed using standard two-dimensional dosimetry and planning. Patients also underwent helical CT of the pelvis for three-dimensional reconstruction of the radiation dose distributions. The systems were loaded with 137Cs sources using the Selectron remote afterloading system according to institutional practice for low-dose-rate brachytherapy. Three-dimensional dose distributions were generated using the Varian BrachyVision treatment planning system. The rectum was contoured from the bottom of the ischial tuberosities to the sigmoid flexure. The entire bladder was contoured. The minimal doses delivered to the 2 cm3 of bladder and rectum receiving the highest dose (DBV2 and DRV2, respectively) were determined from dose-volume histograms, and these estimates were compared with two-dimensionally derived estimates of the doses to the corresponding ICRU reference points. A total of 118 unique intracavitary insertions were performed, and 93 were evaluated and the subject of this analysis. For the rectum, the estimated doses to the ICRU reference point did not differ significantly from the DRV2 (p = 0.561); the mean (+/- standard deviation) difference was 21 cGy (+/- 344 cGy). The median volume of the rectum that received at least the ICRU reference-point dose was 2.1 cm3. In 66 (71%) of 93 cases, <5 cm3 was treated to this dose. However, for the bladder, the estimated doses to the ICRU reference point were significantly lower than the D(BV2) (p <0.001); the mean difference was 680 cGy (+/- 543 cGy). The median volume of the bladder that received at least the ICRU reference-point dose was 13.0 cm3. Our data suggest that the estimated dose to the ICRU rectal point may be a reasonable surrogate for the DRV2. However, this result may not be applicable to other treatment guidelines and ICRT applicator systems. In contrast, the dose to the ICRU bladder point does not appear to be a reasonable surrogate for the DBV2. Correlation with late complications are needed to define the role of three-dimensional dosimetry in treatment planning.