Intensity-modulated Whole Pelvic Radiation Therapy Research Articles

Dosimetric planning study for the prevention of anal complications after post-operative whole pelvic radiotherapy in cervical cancer patients with hemorrhoids.

Radiation-induced anal toxicity can be induced by low radiation doses in patients with haemorrhoids. The object of this study was to determine the dosimetric benefits of different whole pelvic radiotherapy (WPRT) techniques in terms of dose delivered to the anal canal in post-operative patients with cervical cancer. The planning CT images of 10 patients with cervical cancer undergoing postoperative radiotherapy were used for comparison of three different plans. All patients had been treated using the conventional box technique WPRT (CV-WPRT), and we tried low-margin-modified WPRT (LM-WPRT), three-dimensional conformal techniques WPRT (CF-WPRT) and intensity-modulated WPRT (IM-WPRT) planning for dosimetric comparison of the anal canal, retrospectively. Mean anal canal doses of the IM-WPRT were significantly lower (p < 0.05) than those of CV-WPRT, LM-WPRT and CF-WPRT, and V10, V20, V30 and V40 to the anal canal were also significantly lower for IM-WPRT (p < 0.05). The proportion of planning target volumes (PTVs) that received ≥98% of the prescribed dose for all plans was >99%, and the proportion that received ≥108% of the prescribed dose for IM-WPRT was <2%. Volumes of bladders and rectums that received ≥30 or ≥40 Gy were significantly lower for IM-WPRT than for three of the four-field WPRT plans (p = 0.000). IM-WPRT can significantly reduce radiation dose delivered to the anal canal and does not compromise PTV coverage. In patients with haemorrhoids, IM-WPRT may be of value for the prevention of anal complications. Although tolerance of the anal canal tends to be ignored in patients undergoing post-operative WPRT, patients with haemorrhoids may suffer complications at low radiation doses. The present study shows IM-WPRT can be meaningful in these patients.

Intensity-Modulated Whole Pelvic Radiotherapy (IM-WPRT) for Intact Cervical Cancer: Comparison With Conformal 4-Field WPRT and Sensitivity of Organ Sparing Effect to Margin Size

Intensity-Modulated Whole Pelvic Radiotherapy (IM-WPRT) for Intact Cervical Cancer: Comparison With Conformal 4-Field WPRT and Sensitivity of Organ Sparing Effect to Margin Size

SU‐FF‐J‐10: Optimization of Position Compensated Plans (PCPs) for Adaptive Radiotherapy

Purpose: Position compensated plans (PCPs) have been proposed as a method to adapt treatment delivery based on the daily patient position. In this approach, multiple plans are created in which the isocenter is displaced based on anticipated daily offsets. The plan that most closely matches the daily position is then selected for treatment. The goal of this study is to determine the optimal isocenter spacing of PCP for intensity‐modulated whole‐pelvic radiotherapy (IM‐WPRT). Method and Materials: The setup errors for 46 patients treated with IM‐WPRT were measured and the dosimetric effect of these errors on the volume of normal tissue and PTV irradiated was quantified. This analysis demonstrated that the anterior/posterior (AP) setup error had the greatest effect on the change in volume of normal tissue irradiated. Thus, PCPs were created with the isocenter shifted in the ±AP direction. In order to determine the optimal PCP spacing, random errors (σ) were varied from 0.1 to 1.0 cm in steps of 0.1 cm. For each random error, the daily setup deviation was sampled for 25 fractions for 100 hypothetical patients. The PCP correction scheme used the original plan plus two plans with isocenter displacements ranging from 0–2 cm in steps of 0.1 cm. The optimal PCP spacing was defined as the one which minimizes the RMS error in the AP direction. Results: A linear relationship was observed between the random setup error and the optimal PCP spacing. In particular, for the case of two additional PCPs, the required spacing is equal to ±1.22 σ. That is, for a random error of 4 mm, two PCP plans with spacings of ±4.9 mm will minimize the RMS variations in daily setup uncertainties. Conclusion: PCPs with AP isocenter displacements of ±1.22 σ represent an effective means of adapting treatment in IM‐WPRT based on the daily set‐up deviations.

223: Adaptive Treatment Planning Using Position Compensated Plans

Intensity-modulated whole-pelvic radiation therapy (IM-WPRT) has been shown to reduce the volume of normal tissue irradiated in gynecologic patients. However, the full benefits of IM-WPRT may not be realized due to organ motion and setup uncertainty. Recent image-guided technologies allow for the position of the patient to be acquired on a daily basis. The goal of this study is to evaluate a novel adaptive treatment planning technique - the position compensated plan (PCP) - that can be used in conjunction with image-guided radiation therapy (IGRT) in order to reduce the effects of patient positional variations.

Factors influencing bowel sparing in intensity modulated whole pelvic radiotherapy for gynaecological malignancies

Background and purpose To evaluate the influence of uterus and bladder size on large and small bowel sparing with intensity modulated whole pelvic radiotherapy (IM-WPRT) in gynecologic patients. Patients and methods Twenty patients were selected; 10 women with cervical cancer treated with definitive radiotherapy (group ‘DEF’) and 10 endometrial cancer patients treated postoperatively (group ‘POST’). Bladder, rectal wall, small (SB) and large bowel (LB) were delineated as organs at risk. A conformal four field technique and a seven field IMRT plan (prescription dose 50.4 Gy) were compared in terms of DVH and various target parameters. Results At doses between 40 and 50.4 Gy statistically significant improvements ( P<0.05) were observed for IM-WPRT for irradiated volume of rectal wall and bladder. In both patient groups, with IMRT the average irradiated volume of SB was reduced by a factor of 6 at 50.4 Gy. This ratio was 2 for LB. In the DEF group the effect of SB-sparing with IMRT correlated with bladder size (correlation coefficient 0.70) while it did not correlate in the postoperative group. The effect of LB-sparing decreased with increasing bladder size in both groups but the impact of IMRT was larger for postoperative patients. Conclusions IMRT significantly reduced the absolute volume of rectal wall, bladder and bowel irradiated at the prescribed dose level in gynaecologic patients. Main differences between POST and DEF patients receiving IM-WPRT were absolute volumes of LB irradiated to doses between 35 and 50 Gy, suggesting an impact of intact uterus on LB volume in the pelvis. POST patients seem to benefit most from elective nodal IMRT. Bladder filling is an important co-factor influencing the benefit of IMRT with respect to OAR sparing.

Target Volume Definition for Intensity Modulated Whole Pelvic Radiotherapy (IMWPRT)

Purpose/Objective: We are running a phase I trial investigating pelvic nodal dose escalation with IMWPRT that spares tissue irradiated with conformal WPRT. New protocols for target volume definition are required to prevent geographical miss and these must incorporate margins for internal organ motion (IM). IMRT plans are optimised on normal tissue dose volume criteria.

Incorporation of SPECT bone marrow imaging into intensity modulated whole-pelvic radiation therapy treatment planning for gynecologic malignancies

Background and purpose To incorporate single-photon emission computed tomography (SPECT) bone marrow (BM) imaging into the treatment planning process to reduce the volume of BM irradiated in gynecologic patients receiving intensity-modulated whole-pelvic radiation therapy (IM-WPRT). Materials and methods A planning CT scan was obtained of a patient with early stage endometrial cancer. The same patient also underwent a Tc-99m sulfur colloid SPECT scan of the pelvis. Tc-99m sulfur colloid is sequestered by the macrophages in the BM thereby identifying areas of active (red) BM. Using image fusion software, the SPECT scan was aligned with the planning CT scan and used to delineate regions of active BM. An IMRT plan was then generated to provide coverage of the planning target volume (PTV) while sparing areas of active BM and other normal pelvic structures. Results The areas of high active BM density were observed predominantly in the lumbar vertebrae, sacrum and medial iliac crests. IMRT planning reduced the dose to these areas by 50% for doses greater than 30 Gy compared to conventional planning. Furthermore, the IMRT plan did not compromise coverage of the PTV or sparing of normal tissues. Conclusions Our results suggest that SPECT-BM imaging is a useful adjunct to IMRT planning in gynecologic patients undergoing IM-WPRT.

Setup errors in patients treated with intensity-modulated whole pelvic radiation therapy for gynecological malignancies

Intensity-modulated whole pelvic radiation therapy (IM-WPRT) has decreased the incidence of gastrointestinal complications by reducing the volume of normal tissue irradiated in gynecologic patients. However, IM-WPRT plans result in steep dose gradients around the target volume, and thus accurate patient setup is essential. To quantify the accuracy of our patient positioning, we examined the weekly portal films of 46 women treated with IM-WPRT at our institution. All patients were positioned using a customized immobilization device that was indexed to the treatment table. Setup errors were evaluated by comparing portal images to simulation images using an algorithm that registers user-defined open curve segments drawn on both sets of film. The setup errors, which were separated into systematic and random components, ranged from 1.9 to 3.7 mm for the translations and 1.3° to 4.4° for the 2 in-plane translations. The systematic errors were all less than the respective random errors, with the largest error in the anterior/posterior direction. In addition, there was no correlation between the magnitude of these errors and patient-specific factors (age, weight, height). In the future, we will investigate the effect of these setup errors on the delivered dose distribution.

A dosimetric analysis of acute gastrointestinal toxicity in women receiving intensity-modulated whole-pelvic radiation therapy

Purpose: To identify dosimetric factors correlated with acute gastrointestinal (GI) toxicity in gynecology patients undergoing intensity-modulated whole pelvic radiation therapy (IM-WPRT). Material and methods: Fifty gynecology patients received IM-WPRT (45–1.8 Gy/fraction) between 2/00 and 3/02. All patients were treated to a clinical target volume (CTV) consisting of the upper vagina, parametria, uterus, presacral region and pelvic lymph nodes. Grade 2 acute GI toxicity requiring frequent medications and grade 3–5 toxicities were designated as clinically significant and analyzed as a function of patient and dosimetric variables. The most significant volumetric factors were fit to a normal tissue complication probability (NTCP) function. Results: Fourteen women (28%) developed clinically significant acute GI toxicity. None of the patient factors were correlated with acute GI toxicity. In addition, the volume of rectum receiving 25, 50, 75, 90, 100 and 110% of the prescription dose did not reach statistical significance. In contrast, a correlation was observed between the volume of small bowel (SB) irradiated and acute GI toxicity, particularly the SB volumes receiving 90 and 100% of the prescription dose ( p=0.009 and p=0.009, respectively). Controlling for patient and other dosimetric factors, the SB volume receiving the 100% (Vol SB,100) of the prescription dose remained the sole significant factor on multivariate analysis ( p=0.012). Subsequently, a NTCP curve, quantifying the risk of acute GI toxicity, was generated based on the Vol SB,100. Conclusions: The most significant factor correlated acute GI toxicity in gynecology patients undergoing IM-WPRT is Vol SB,100.

Preliminary analysis of chronic gastrointestinal toxicity in gynecology patients treated with intensity-modulated whole pelvic radiation therapy

Purpose To provide a preliminary analysis of chronic gastrointestinal (GI) toxicity in gynecology patients treated with intensity-modulated whole pelvic radiation therapy (IM-WPRT). Methods and materials Between February 2000 and August 2001, 36 gynecology patients received IM-WPRT. All patients underwent a contrast-enhanced computed tomography scan, and a clinical target volume (CTV) was contoured consisting of the upper vagina, parametria, uterus (if present), and presacral and pelvic lymph node regions. The CTV was expanded by 1 cm to create a planning target volume (PTV). Seven or 9-field IM-WPRT plans were generated. IM-WPRT plans were highly conformal, providing excellent coverage of the PTV and considerable sparing of normal tissues, including the small bowel and rectum. Chronic GI toxicity was scored: 0 (no symptoms), 1 (mild symptoms, no medications required), 2 (moderate symptoms, medications required), and 3 (severe symptoms, hospitalization, surgery required). Chronic GI toxicity in 30 gynecology patients treated with conventional WPRT patients before the implementation of IM-WPRT was also evaluated. Median follow-up in the IM-WPRT and WPRT groups were 19.6 and 30.2 months, respectively. Results The IM-WPRT and WPRT groups were well balanced in terms of most patient and treatment factors, including age, site, stage, chemotherapy, WPRT dose, and brachytherapy, except for a higher frequency of surgery (75 vs. 54%, p = 0.02) in the IM-WPRT group. Overall, IM-WPRT patients had a lower rate of chronic GI toxicity (11.1 vs. 50.0%, p = 0.001) than WPRT patients. The percentage of IM-WPRT patients with Grade 1, 2, and 3 toxicity were 8.3%, 2.8%, and 0%, respectively. Corresponding percentages in the WPRT group were 30.0%, 16.7%, and 3.3%, respectively. The only other factor correlated with chronic GI toxicity was age ( p = 0.02). On multivariate (logistic regression) analysis controlling for age and other clinical factors, IM-WPRT retained its statistical significance ( p = 0.01; odds ratio 0.16; 95% confidence interval 0.04, 0.67) Conclusions Our results suggest that IM-WPRT is associated with less chronic GI toxicity than conventional WPRT in patients with gynecologic malignancies. However, longer follow-up and more patients are clearly needed to ascertain whether the benefits of IM-WPRT treatment seen here translate into true long-term reductions in chronic GI toxicity.

Impact of intensity-modulated radiotherapy on acute hematologic toxicity in women with gynecologic malignancies

Purpose: To evaluate the impact of intensity-modulated whole pelvic radiotherapy (IM-WPRT) on acute hematologic toxicity (HT) in gynecology patients.Methods and Materials: Between February 2000 and June 2001, 36 patients (24 cervix, 12 uterus) received IM-WPRT. The target consisted of the upper vagina, parametria, uterus, and presacral and pelvic lymph nodes. Using commercially available software, seven or nine coplanar IM-WPRT plans were generated. The planning goals were to irradiate the target while minimizing the dose to the small bowel, bladder, and rectum. Pelvic bone marrow (BM) was not a constraint in the planning process. The variables analyzed included white blood count (WBC), absolute neutrophil count (ANC), platelets, and hemoglobin (Hgb) obtained before and weekly during RT. As a comparison, the HT in 88 patients (44 cervix, 44 uterus) treated to the same target volume and total dose (45 Gy) with conventional four-field WPRT was analyzed. In addition, the medullary spaces within the pelvic bones in 10 women were contoured and the average dose-volume histograms representing the pelvic BM were compared between the two groups.Results: IM-WPRT patients had a lower median age (p = 0.008), higher percentage of squamous histologic features (p = 0.04), and were more likely to receive chemotherapy (CTX) (p = 0.02) than were the WPRT patients. No differences were seen in the baseline WBC, ANC, platelet, or Hgb levels between the two groups. Grade 2 or greater WBC, ANC, and Hgb toxicity was seen in 19.4%, 9.1%, and 8.6% of the IM-WPRT patients, respectively. Comparable rates were seen in the WPRT patients (WBC 21.6%, p = 0.79; ANC 8.3%, p = 0.91; Hgb 9.2%, p = 0.94). No Grade 2 or greater platelet toxicity was seen in either group. Significant HT was infrequent in women treated with RT alone and was comparable in the two groups. In contrast, WPRT + CTX patients experienced more Grade 2 or greater WBC toxicity (60% vs. 31.2%, p = 0.08) and developed lower median WBC (2.8 vs. 3.6 μg/dL, p = 0.05) and ANC (1874 vs. 2669, p = 0.04) nadirs than did IM-WPRT + CTX patients. Moreover, CTX was held more often in the WPRT group secondary to HT (40% vs. 12.5%, p = 0.06). Although Grade 2 or greater ANC (23.5% vs. 15.3%) and Hgb (35.2% vs. 15.2%) toxicity were lower in the IM-WPRT + CTX group, these differences did not reach statistical significance (p = 0.58 and p = 0.22, respectively). The comparison of pelvic BM dose-volume histograms revealed that IM-WPRT planning resulted in significantly less BM volume being irradiated compared with WPRT planning, particularly within the iliac crests.Conclusion: IM-WPRT has a favorable impact on the risk of acute HT in gynecology patients, particularly in those receiving CTX. Future work is needed to optimize BM sparing in these patients to reduce the risk of significant HT further.

Chronic gastrointestinal toxicity in gynecology patients treated with intensity-modulated whole pelvic radiation therapy: a preliminary analysis

Purpose/Objective: Intensity-modulated whole pelvic radiation therapy (IM-WPRT) has been shown to reduce the volume of small bowel and rectum irradiated and the risk of acute gastrointestinal (GI) toxicity in gynecology patients. To date, however, no data are available evaluating the risk of chronic toxicity in these women. The purpose of this study is to provide a preliminary analysis of chronic GI toxicity in gynecology patients treated with IM-WPRT at our institution.

Intensity-modulated whole pelvic radiotherapy in women with gynecologic malignancies

Purpose: To describe our initial clinical experience with intensity-modulated whole pelvic radiotherapy (IM-WPRT) in women with gynecologic malignancies. Methods and Materials: Between February 2000 and August 2001, 40 gynecology patients underwent IM-WPRT. After fabrication of customized immobilization, all patients underwent contrast-enhanced CT, and a clinical target volume was contoured consisting of the upper vagina, parametria, uterus (if present), and presacral and pelvic lymph node regions. The clinical target volume was expanded by 1 cm to create a planning target volume (PTV). Using commercially available software, 7- or 9-field, 6-MV, coplanar IM-WPRT plans were generated for all patients. The worst acute gastrointestinal and genitourinary toxicity during treatment was scored on a 4-point scale: 0, none; 1, mild, no medications required; 2, moderate, medications required; and 3, severe, treatment breaks or cessation, hospitalization. As a comparison, acute toxicities in 35 previously treated conventional WPRT patients were analyzed. No significant differences were noted in the clinicopathologic and treatment factors between the two groups. Results: IM-WPRT plans provided excellent PTV coverage, with considerable sparing of the surrounding normal tissues. On average, 98.1% of the PTV received the prescription dose. The average percentage of the PTV receiving 110% and 115% of the prescription dose was 9.8% and 0.2%, respectively. IM-WPRT was well tolerated, with no patient developing Grade 3 toxicity. Grade 2 acute gastrointestinal toxicity was less common in the IM-WPRT group (60 vs. 91%, p = 0.002) than in the conventional WPRT group. Moreover, the percentage of IM-WPRT and WPRT patients requiring no or only infrequent antidiarrheal medications was 75% and 34%, respectively ( p = 0.001). Although less Grade 2 genitourinary toxicity was seen in the IM-WPRT group (10% vs. 20%), this difference was not statistically significant ( p = 0.22). Conclusion: IM-WPRT is a promising approach in gynecology patients. IMRT planning resulted in excellent PTV coverage, with considerable sparing of normal tissues. Treatment was well tolerated and associated with less acute gastrointestinal sequelae than conventional WPRT. Longer follow-up and more patients are needed, however, to evaluate the full merits of this novel approach.

Intensity-modulated radiation therapy as a means of reducing dose to bone marrow in gynecologic patients receiving whole pelvic radiation therapy

Purpose: Whole pelvic radiation therapy (WPRT) is commonly used in gynecologic malignancies. However, WPRT results in irradiation of a considerable volume of the surrounding normal tissues including small bowel and pelvic bone marrow (BM). While BM suppression is not typically significant following WPRT alone, it is common in patients who receive chemotherapy. Recent data have demonstrated that intensity-modulated WPRT (IM-WPRT) significantly reduces the volume of small bowel, bladder and rectum receiving the prescription dose in gynecology patients. The purpose of this study is to evaluate IM-WPRT as a means to reduce the volume of pelvic BM irradiated. Materials and methods: Ten women with cervical or endometrial cancer previously treated using IM-WPRT were selected for this analysis. Using the treatment planning computed tomography scan, the clinical target volume (CTV) was defined to encompass the gross tumor, parametrial tissues, uterus (if present) and the regional lymph nodes. The CTV was expanded by a 1 cm margin to form the planning target volume (PTV). The bladder, rectum, small bowel were delineated in each patient. BM in the iliac crests was also contoured since studies have shown that the majority of the pelvic BM is located in these sites. Two plans were created for each patient: a standard 4-field WPRT plan with apertures shaped to the PTV in each beam’s-eye view, and an IM-WPRT plan designed to conform dose to the PTV while minimizing the dose to the normal tissues including the BM. Dose volume histograms (DVHs) for the PTV, small bowel and BM were compared for each patient. Results: For each of the ten patients, IM-WPRT treatment plans demonstrated a significant reduction of the volume of the BM receiving greater than 30% of the prescription dose (13.5 Gy). The attached table shows the average volume of the BM in the iliac crests receiving the specified dose (or greater) for the 4-field WPRT and the BM-sparing IM-WPRT plans. On average, IM-WPRT resulted in a 50% reduction in the volume of BM irradiated to doses greater than 22.5 Gy (p < 0.001), and more than 60% reduction of the BM irradiated to doses greater than 31.5 Gy (p < 0.001). Furthermore, as expected, the BM-sparing IM-WPRT plans resulted in significant sparing of all other normal tissues that was comparable to the original IM-WPRT that did not specifically consider BM as a constraint. In all ten cases, the BM-sparing treatment plan did not result in any significant differences in the PTV and small bowel DVHs. Conclusion: IM-WPRT significantly reduces the volume of pelvic BM irradiated compared to conventional WPRT. In addition, BM-sparing IM-WPRT did not compromise the improvements previously seen in IM-WPRT treatment plans that did not consider BM. Currently patients are being treated with this BM-sparing technique to determine if the dosimetric improvements seen here translate into clinical benefits. Tabled 1Dose Gy (%)WPRT (% BM Volume)BM-Sparing IM-WPRT (% BM volume)p-value9.0 (20%)95.8%98.5%< 0.00113.5 (30%)92.3%90.4%0.3522.5 (50%)87.0%43.7%< 0.00131.5 (70%)52.8%25.9%< 0.00140.5 (90%)42.5%12.1%< 0.00145.0 (100%)33.0%4.5%< 0.001 Open table in a new tab

Dose-volume histogram analysis of acute gastrointestinal toxicity for gynecologic patients receiving intensity-modulated whole pelvic radiotherapy

Purpose: Gastrointestinal (GI) sequelae are among the most common side effects in gynecologic patients receiving whole pelvic radiotherapy (WPRT). Recently, it has been reported that intensity-modulated whole pelvic radiotherapy (IM-WPRT) reduces the volume of the small bowel and rectum irradiated in these women. However, since introducing IM-WPRT in our clinic, we have noted a broad range of acute GI toxicities. To better understand and minimize these sequelae, the goal of this study is to correlate acute GI toxicity with features of the small bowel and rectal dose-volume histograms (DVHs).

Clinical experience with Intensity-Modulated Whole Pelvic Radiation Therapy (IM-WPRT) in patients with gynecologic malignancies

Clinical experience with Intensity-Modulated Whole Pelvic Radiation Therapy (IM-WPRT) in patients with gynecologic malignancies