Feasibility of dose escalation using intensity-modulated radiotherapy in posthysterectomy cervical carcinoma

Feasibility and Outcome of Concurrent Chemoradiotherapy for Recurrent Cervical Carcinoma after Initial Surgery

Aims and background

The prognosis for recurrent cervical carcinoma following initial surgery is dismal even when aggressive radiotherapy or salvage surgery is used. We retrospectively reviewed hospital records to evaluate the efficacy and feasibility of concurrent chemoradiotherapy as a salvage treatment.

Methods

From 1999 to 2007, 47 patients received salvage chemoradiotherapy. Involved-field irradiation was delivered at a median dose of 64.8 Gy (range, 36–100.2), including brachytherapy boost in 10 patients. Pelvic re-irradiation was performed in 4 of the 12 women who had a previous history of pelvic radiotherapy. All but one patient received cisplatin-based concomitant chemotherapy during radiotherapy.

Results

The median overall follow-up period was 27 months and for surviving patients was 57 months. The interval between initial surgery and recurrence was 22 months (range, 4–203), and the median recurrent mass size was 4 cm (range, 0.5–11). In 34 patients, recurrent tumors were confined to the pelvis (21 central and 13 peripheral). Grade 3–4 acute hematologic toxicity was the most frequent toxicity and was observed in 29 (62%) women. Five-year actuarial cumulative incidence of severe gastrointestinal and genitourinary toxicity was 13% and 7%, respectively. Thirty-three patients (70%) showed a complete response and 9 (19%) a partial response following salvage chemoradiation. Five-year overall and disease-free survival rates were 44% and 41%, respectively.

Conclusions

Salvage chemoradiotherapy appears to be a feasible treatment option for women with recurrent cervical carcinoma following surgery. The treatment had a high salvage rate and acceptable late complication rate, despite being associated with substantial acute toxicity.

Adjuvant chemotherapy for early-stage cervical cancer

The aim of this review is to address the current status of adjuvant chemotherapy alone in early-stage cervical cancer treatments in the literature. At present, the therapeutic effect of adjuvant chemotherapy alone after radical surgery (RS) has not yet been established, and radiation therapy (RT) or concurrent chemoradiotherapy (CCRT) is recommended as the standard adjuvant therapy after RS for early-stage cervical cancer in various guidelines. The main purpose of adjuvant therapy after RS, however, should be to reduce extrapelvic recurrence rather than local recurrence, although adjuvant RT or CCRT has survival benefits for patients with intermediate- or high-risk factors for recurrence. Moreover, several studies reported that adjuvant therapies including RT were associated with a higher incidence of complications, such as lymphedema, bowel obstruction and urinary disturbance, and a lower grade of long-term quality of life (QOL) or sexual functioning than adjuvant chemotherapy alone. The effect of adjuvant chemotherapy alone for early-stage cervical cancer with intermediate- or high-risk factors for recurrence were not fully investigated in prospective studies, but several retrospective studies suggest that the adjuvant effects of chemotherapy alone are at least similar to that of RT or CCRT in terms of recurrence rate, disease-free survival, or overall survival (OS) with lower incidence of complications. Whereas cisplatin based combination regimens were used in these studies, paclitaxel/cisplatin (TP) regimen, which is currently recognized as a standard chemotherapy regimen for patients with metastatic, recurrent or persistent cervical cancer by Gynecologic Oncology Group (GOG), had also survival benefit as an adjuvant therapy. Therefore, it may be worth considering a prospective randomized controlled trial (RCT) of adjuvant chemotherapy alone using TP regimen versus adjuvant RT as an alternative adjuvant therapy. Because early-stage cervical cancer is a curable condition, it is necessary that the therapeutic strategies should be improved with considering adverse events and QOL for long-term survivors.

The Treatment of Pelvic Locoregional Recurrence of Cervical Cancer After Radical Surgery With Intensity-Modulated Radiation Therapy Compared With Conventional Radiotherapy: A Retrospective Study

Objective

The aim of this study was to investigate the therapeutic response and toxicity of intensity-modulated radiation therapy (IMRT) or conventional radiotherapy (c-RT) as adjuvant therapy in patients with pelvic locoregional recurrence of cervical cancer after radical surgery.

Methods

This retrospective study included 161 patients with unresectable pelvic locoregional recurrence of cervical cancer after radical surgery between March 2003 and May 2012. All patients were initially diagnosed with International Federation of Gynecology and Obstetrics stage IB-IIA cervical cancer and received radical hysterectomy and pelvic lymphadenectomy. A total of 82 patients were treated with c-RT, whereas the remaining 79 patients underwent IMRT. Intracavitary brachytherapy and concurrent chemotherapy were performed during external irradiation.

Results

The mean dose delivered to the planning target volume was significantly higher in the IMRT group than in the c-RT group (61.8 vs 50.3 Gy,P= 0.029). Intensity-modulated radiation therapy plans yielded better dose sparing of small bowel, bladder, and rectum than did c-RT (P< 0.05). Moreover, the IMRT patients experienced less acute and chronic toxicities (P< 0.05) and better short-term effects (complete response + partial response) than did those treated with c-RT (89.9% vs 63.4%,P= 0.03). Three- and 5-year overall survival rates were significantly higher in the IMRT group than in the c-RT group (3-year: 58.4% vs 39.1%,P= 0.012; 5-year: 35.4% vs 21.4%,P= 0.007). Furthermore, 5-year progression-free survival rates were significantly higher in the IMRT group than in the c-RT group (26.1% vs 15.1%,P= 0.031).

Conclusions

Intensity-modulated radiation therapy achieved outcomes superior to c-RT in patients with pelvic locoregional recurrence of cervical cancer after radical surgery. The acute and chronic toxicities were acceptable, and the adjacent organs at risk were well protected.

Effect of different treatment plans on irradiated small-bowel volume in gynecologic patients undergoing whole-pelvic irradiation

To evaluate the effect of different treatment plans for whole-pelvic irradiation on small-bowel volumes (SBVs) in patients with gynecologic malignancies, 40 patients were enrolled in this study. Computed tomography (CT) simulations were performed, and the small bowel of each patient was outlined manually. Treatment plans with equal-weighted (EW) and non-equal-weighted (NEW) (70% in bilateral directions) techniques of four-field and intensity-modulated radiation therapy (IMRT) were performed. The V10-V100 represented the volume (cm³) at different levels of the prescribed doses (10-100%). The V10-V100 was compared among the different treatment planning techniques, and patients who were suitable for IMRT or NEW were identified. IMRT and NEW significantly reduced the V50-V100 and V40-V60 levels compared with EW, respectively. NEW caused a significant reduction in the V30-V60 levels in patients with a BMI ≥26 kg/m². Patients with IMRT demonstrated lower V70-V100 levels compared with those with NEW. In patients with a BMI ≥26 kg/m² or an age ≥55 years, lower V20-V50 levels were noted using NEW compared with IMRT. Treatment planning with larger weighting in the bilateral directions in four-field radiotherapy reduces the low-dose SBV in patients with gynecologic malignancies, especially in those with a high BMI or the elderly. IMRT effectively reduces high-dose SBV, especially in patients with a low BMI.

Dosimetric comparison of intensity modulated radiotherapy and three-dimensional conformal radiotherapy in patients with gynecologic malignancies: a systematic review and meta-analysis

BACKGROUND

To quantitatively evaluate the safety and related-toxicities of intensity modulated radiotherapy (IMRT) dose-volume histograms (DVHs), as compared to the conventional three-dimensional conformal radiotherapy (3D-CRT), in gynecologic malignancy patients by systematic review of the related publications and meta-analysis.

METHODS

Relevant articles were retrieved from the PubMed, Embase, and Cochrane Library databases up to August 2011. Two independent reviewers assessed the included studies and extracted data. Pooled average percent irradiated volumes of adjacent non-cancerous tissues were calculated and compared between IMRT and 3D-CRT for a range of common radiation doses (5-45 Gy).

RESULTS

In total, 13 articles comprised of 222 IMRT-treated and 233 3D-CRT-treated patients were included. For rectum receiving doses ≥30 Gy, the IMRT pooled average irradiated volumes were less than those from 3D-CRT by 26.40% (30 Gy, p = 0.004), 27.00% (35 Gy, p = 0.040), 37.30% (40 Gy, p = 0.006), and 39.50% (45 Gy, p = 0.002). Reduction in irradiated small bowel was also observed for IMRT-delivered 40 Gy and 45 Gy (by 17.80% (p = 0.043) and 17.30% (p = 0.012), respectively), as compared with 3D-CRT. However, there were no significant differences in the IMRT and 3D-CRT pooled average percent volumes of irradiated small bowel or rectum from lower doses, or in the bladder or bone marrow from any of the doses. IMRT-treated patients did not experience more severe acute or chronic toxicities than 3D-CRT-treated patients.

CONCLUSIONS

IMRT-delivered high radiation dose produced significantly less average percent volumes of irradiated rectum and small bowel than 3D-CRT, but did not differentially affect the average percent volumes in the bladder and bone marrow.

Rectum separation in patients with cervical cancer for treatment planning in primary chemo-radiation

PURPOSE

To proof feasibility of hydrogel application in patients with advanced cervical cancer undergoing chemo-radiation in order to reduce rectal toxicity from external beam radiation as well as brachytherapy.

MATERIAL AND METHODS

Under transrectal sonographic guidance five patients with proven cervical cancer underwent hydro gel (20 cc) instillation into the tip of rectovaginal septum adherent to posterior part of the visible cervical tumor. Five days after this procedure all patients underwent T2 weighted transversal and sagittal MRI for brachytherapy planning. MRI protocol included T2 weighted fast spin echo (FSE) imaging in sagittal, coronal and para-axial orientation using an 1.5 Tesla MRI. Separation of anterior rectal wall and cervix was documented.

RESULTS

Hydrogel application was uneventful in all patients and no toxicity was reported. Separation ranged from 7 to 26 mm in width (median 10 mm). The length of the separation varied between 18 and 38 mm (median 32 mm). In all patients displacement was seen in the posterior vaginal fornix, and/or at the deepest part of uterine cervix depending on the extension of the cul-de-sac in correlation to the posterior wall of the uterus. In patients with bulky tumor and/or deep (vaginal) extend of peritoneal cavity tumour was seen mainly cranial from the rectovaginal space and therefore above the hydrogeI application. Only in the extra-peritoneal (lower) part of the cervix a good separation could be achieved between the rectum and cervix.

CONCLUSION

Hydrgel instillation in patients with cervial cancer undergoing chemoradiation is safe and feasible. Because of the loose tissue of the cul-de-sac and its intra- and extraperitoneal part, hydrogel instillation of 20 cc did not result in a sufficient separation of the cervix from anterior wall.

[Dosimetric comparison between the intensity modulated radiotherapy with fixed field and Rapid Arc of cervix cancer]

PURPOSE

Concurrent radiochemotherapy is the standard treatment for locally advanced cervical cancer. This treatment is responsible for bowel and hematologic toxicities. The use of intensity-modulated radiotherapy (IMRT), in static beams, allows a decrease of this toxicity. The technique of RapidArc(®) IMRT could lower the dose delivered to the organs at risk and improve the homogeneity of the planning target volume coverage, while decreasing the processing time.

PATIENTS AND MATERIALS

For 20 patients, treatment plans performed with IMRT and RapidArc(®) were compared. The target volumes were: the clinical target volume (gross tumour volume, uterus, upper third of the vagina, the hypogastric, iliac and presacral nodal regions), and the planning target volume (clinical target volume+1cm). The delineated organs at risk were: rectum, bladder, bowel and bone marrow. The dose was 45 Gy in 25 fractions. IMRT were delivered with five beams and RapidArc(®) with two arcs. The comparisons were made by the non-parametric test of Wilcoxon.

RESULTS

Medium coverage of the planning target volume was better with RapidArc(®) (P=0.01). It was also better regarding the sparing of bowel (P=0.01) and IMRT was better regarding the sparing of bladder (P=0.01) and rectum (P=0.05). The total volume receiving 20 Gy was less important with RapidArc(®) (P<0.001). RapidArc(®) allowed to decrease the treatment time (3 versus 12 minutes with IMRT) and the number of monitor units (MU) (376.5 versus 962.2, on average, P=0.0001).

CONCLUSION

The technique of RapidArc(®) seems to obtain better dosimetric results compared to RCMI, with fewer MU, and a significant decrease in treatment time.

Full-dose adjuvant postoperative radiation therapy for retroperitoneal sarcomas

OBJECTIVES

To categorize sites of recurrence of retroperitoneal sarcomas (RPS) and correlate to clinical treatment volumes of postoperative radiation therapy (PORT) with or without intraoperative radiation therapy (IORT).

METHODS

A retrospective review of patients with RPS who received PORT between 1990 and 2008 was done. Tumor recurrences were subdivided as local tumor bed, regional adjacent retroperitoneal fascial tissues, peritoneal diffuse seeding, and distant metastases.

RESULTS

PORT was given to 33 patients, 20 of whom also received IORT. Local recurrences appeared in 4 (12%) cases. Regional recurrences appeared in 8 (26%) cases, including 5 with in-field recurrence and 3 with edge-of-field recurrence. Edge-of-field recurrences developed in 3 of 11 (27%) patients whose clinical presentation was local recurrence compared with none of 20 patients whose clinical presentation was a primary tumor (P=0.037). Late grades 3 to 4 gastrointestinal toxicities appeared in 1 of 10 (10%) patients who received intensity-modulated radiation therapy (IMRT) with a minimum 15-month follow-up compared with 4 of 15 (27%) patients who received standard RT.

CONCLUSIONS

Use of techniques such as IORT and IMRT can deliver a dose of approximately 60 Gy to the tumor bed and 44 to 51 Gy to the surrounding retroperitoneal fascial planes. Acute and late gastrointestinal toxicities were less frequent with IMRT compared with conventional PORT with IORT. These results may provide the basis for comparison of various adjuvant therapy strategies for RPS. As radiation therapy is a loco-regional treatment, results should be reported by tumor recurrence subtypes of local, regional, peritoneal, and distant.

Dosimetric comparison of high dose rate brachytherapy and intensity-modulated radiation therapy for cervical carcinoma

Intracavitary brachytherapy is an integral part of radiotherapy for locally advanced gynecologic malignancies. A dosimetric intercomparison of high dose rate intracavitary brachytherapy (HDR_BT) and intensity-modulated radiotherapy in cervical carcinoma has been made in the present study. CT scan images of 10 patients treated with HDR_BT were used for this study. A sliding-window IMRT (IMRT_SW) and step-and-shoot IMRT plans were generated using 6-MV X-rays. The cumulative dose volume histograms of target, bladder, rectum and normal tissue were analyzed for both techniques and dose distributions were compared. It was seen that the pear-shaped dose distribution characteristic of intracavitary brachytherapy with sharp dose fall-off outside the target could be achieved with IMRT. The integral dose to planning target volume was significantly higher with HDR_BT in comparison with IMRT. Significant differences between the two techniques were seen for doses to 1 cc and 2 cc of rectum, while the differences in 1 cc and 2 cc doses to bladder were not significant. The integral doses to the nontarget critical and normal structures were smaller with HDR_BT and with IMRT. It is concluded that IMRT can be the choice of treatment in case of non-availability of HDR brachytherapy facilities or when noninvasive treatments are preferred

Comparison of conformal and intensity modulated radiation therapy techniques for treatment of pelvic tumors. Analysis of acute toxicity

Background

This retrospective analysis reports on the comparative outcome of acute gastrointestinal (GI) and genitourinary (GU) toxicities between conformal radiation therapy (CRT) and intensity modulated radiation therapy (IMRT) techniques in the treatment of patients with pelvic tumors.

Methods

From January 2002 to December 2008, 69 patients with pelvic tumors underwent whole pelvic CRT and 65 underwent whole pelvic IMRT to treat pelvic lymph nodes and primary tumor regions. Total dose to the whole pelvis ranged from 50 to 50.4 Gy in 25 to 28 daily fractions. Chemotherapy (CT) regimen, when employed, was based upon primary tumor. Acute GI and GU toxicities were graded by RTOG/EORTC acute radiation morbidity criteria.

Results

Absence of GI symptoms during radiotherapy (grade 0) was more frequently observed in the IMRT group (43.1% versus 8.7; p < 0.001) and medication for diarrhea (Grade 2) was more frequently used in the CRT group (65.2% versus 38.5%; p = 0.002). Acute GI grade 1 and 3 side effects incidence was similar in both groups (18.5% versus 18.8%; p = 0.95 and 0% versus 7.2%; p = 0.058, respectively). Incidence of GU toxicity was similar in both groups (grade 0: 61.5% versus 66.6%, p = 0.54; grade 1: 20% versus 8.7%, p = 0.06; grade 2: 18.5% versus 23.5%, p = 0.50 and grade 3: 0% versus 1.5%, p > 0.99).

Conclusions

This comparative case series shows less grade 2 acute GI toxicity in patients treated with whole pelvic IMRT in comparison with those treated with CRT. Incidence of acute GU toxicity was similar in both groups.

Intensity-modulated radiotherapy in patients with cervical cancer. An intra-individual comparison of prone and supine positioning

Background

Chemoradiation for cervical cancer patients is associated with considerable gastrointestinal toxicity. Intensity-modulated radiotherapy (IMRT) has demonstrated superiority in terms of target coverage and normal tissue sparing in comparison to conventional 3D planning in gynaecological malignancies. Whether IMRT in prone (PP) or supine position (SP) might be beneficial for cervical cancer patients remains partially unanswered.

Methods

10 patients on FIGO stage IB-III cervical cancer, 6 patients for definitive and 4 patients for adjuvant external beam pelvic RT, were planned in PP and SP using a 7-field IMRT technique. IMRT plans for PP and SP (mean dose, D_mean 50.4 Gy) were optimized in terms of PTV coverage (1^st priority) and small bowel sparing (2^nd priority). A comparison of DVH parameters for PTV, small bowel, bladder, and rectum was performed.

Results

The comparison showed a similar PTV coverage of 95% of the prescribed dose and for target conformity in IMRT plans (PP, SP). PTV, rectum and bladder volumes were comparable for PP and SP. Significantly larger volumes of small bowel were found in PP (436 cc, + 35%, p = 0.01). PP decreased the volume of small bowel at 20-50.4 Gy (p < 0.05) and increased the rectum volumes covered by doses from 10-40 Gy (p < 0.01), the V50.4 was < 5% in both treatment positions. Bladder sparing was significant better at 50.4 Gy (p = 0.03) for PP.

Conclusion

In this dosimetric study, we demonstrated that pelvic IMRT in prone position for patients with cervical cancer seems to be beneficial in reducing small bowel volume at doses ≥20 Gy while providing similar target coverage and target conformity. The use of frequent image guidance with KV (kilovolt) or MV (megavolt) computertomography can reduce set-up deviations, and treatment in prone position can be done with a higher set-up accuracy. Clinical outcome studies are needed to affirm lower toxicity.

Pattern of failure in bladder cancer patients treated with radical cystectomy: rationale for adjuvant radiotherapy

Thus far, the role of adjuvant radiotherapy (RT) after radical cystectomy (RC) in urinary bladder cancer patients has yet to be defined. The purpose of this study is to analyze patterns of failure, and suggest the rationale for RT. Between 1986 and 2005, a total of 259 patients treated with RC and pelvic lymph node dissection was enrolled. The age range was 27-82 yr (median, 62 yr). Node positivity increased according to tumor staging. Patients were divided into the following two groups based on pathologic analysis: organ-confined disease group (n=135) and extravesical/lymph node-positive disease group (n=80). Pelvic failures (PF) were observed in 8 (4.9%) in organ-confined disease group, and 21 (21.7%) in extravesical/lymph node-positive disease group. Five-year PF-free survival rates were 91.2% in organ-confined disease group and 68.0% in extravesical/lymph node-positive disease group. Five-year cancer-specific survival rates were 86.2% in organ-confined disease group and 53.9% in extravesical/lymph node-positive disease group. In conclusion, a relatively high PF rate was observed in extravesical lymph node-negative and lymph node-positive disease patients in this study. Adjuvant pelvic RT may be considered to reduce pelvic failures in extravesical lymph node-positive bladder cancer. Future prospective trials are required to test the clinical benefit of adjuvant RT.

Intensity-modulated arc therapy with simultaneous integrated boost in the treatment of primary irresectable cervical cancer. Treatment planning, quality control, and clinical implementation

PURPOSE

To report on the planning procedure, quality control, and clinical implementation of intensity-modulated arc therapy (IMAT) delivering a simultaneous integrated boost (SIB) in patients with primary irresectable cervix carcinoma.

PATIENTS AND METHODS

Six patients underwent PET-CT (positron emission tomography-computed tomography) and MRI (magnetic resonance imaging) before treatment planning. Prescription (25 fractions) was (1) a median dose (D(50)) of 62, 58 and 56 Gy to the primary tumor (GTV_cervix), primary clinical target volume (CTV_cervix) and its planning target volume (PTV_cervix), respectively; (2) a D(50) of 60 Gy to the PET-positive lymph nodes (GTV_nodes); (3) a minimal dose (D(98)) of 45 Gy to the planning target volume of the elective lymph nodes (PTV_nodes). IMAT plans were generated using an anatomy-based exclusion tool with the aid of weight and leaf position optimization. The dosimetric delivery of IMAT was validated preclinically using radiochromic film dosimetry.

RESULTS

Five to nine arcs were needed to create valid IMAT plans. Dose constraints on D(50) were not met in two patients (both GTV_cervix: 1 Gy and 3 Gy less). D(98) for PTV_nodes was not met in three patients (1 Gy each). Film dosimetry showed excellent gamma evaluation. There were no treatment interruptions.

CONCLUSION

IMAT allows delivering an SIB to the macroscopic tumor without compromising the dose to the elective lymph nodes or the organs at risk. The clinical implementation is feasible.

3D-Conformal versus intensity-modulated postoperative radiotherapy of vaginal vault: A dosimetric comparison

We evaluated a step-and-shoot IMRT plan in the postoperative irradiation of the vaginal vault compared with equispaced beam arrangements (3-5) 3D-radiotherapy (RT) optimized plans. Twelve patients were included in this analysis. Four plans for each patient were compared in terms of dose-volume histograms, homogeneity index (HI), and conformity index (CI): (1) 3 equispaced beam arrangement 3D-RT; (2) 4 equispaced beam arrangement 3D-RT; (3) 5 equispaced beam arrangement 3D-RT; (4) step-and-shoot IMRT technique. CI showed a good discrimination between the four plans. The mean scores of CI were 0.58 (range: 0.38-0.67) for the 3F-CRT plan, 0.58 (range: 0.41-0.66) for 4F-CRT, 0.62 (range: 0.43-0.68) for 5F-CRT and 0.69 (range: 0.58-0.78) for the IMRT plan. A significant improvement of the conformity was reached by the IMRT plan (p < 0.001 for all comparisons). As expected, the increment of 3D-CRT fields was associated with an improvement of target dose conformity and homogeneity; on the contrary, in the IMRT plans, a better conformity was associated to a worse target dose homogeneity. A significant reduction in terms of D(mean), V90%, V95%, V100% was recorded for rectal and bladder irradiation with the IMRT plan. Surprisingly, IMRT supplied a significant dose reduction also for rectum and bladder V30% and V50%. A significant dosimetric advantage of IMRT over 3D-RT in the adjuvant treatment of vaginal vault alone in terms of treatment conformity and rectum and bladder sparing is shown.

Effect of intensity-modulated pelvic radiotherapy on second cancer risk in the postoperative treatment of endometrial and cervical cancer

PURPOSE

To estimate and compare intensity-modulated radiotherapy (IMRT) with three-dimensional conformal radiotherapy (3DCRT) in terms of second cancer risk (SCR) for postoperative treatment of endometrial and cervical cancer.

METHODS AND MATERIALS

To estimate SCR, the organ equivalent dose concept with a linear-exponential, a plateau, and a linear dose-response model was applied to dose distributions, calculated in a planning computed tomography scan of a 68-year-old woman. Three plans were computed: four-field 18-MV 3DCRT and nine-field IMRT with 6- and 18-MV photons. SCR was estimated as a function of target dose (50.4 Gy/28 fractions) in organs of interest according to the International Commission on Radiological Protection.

RESULTS

Cumulative SCR relative to 3DCRT was +6% (3% for a plateau model, -4% for a linear model) for 6-MV IMRT and +26% (25%, 4%) for the 18-MV IMRT plan. For an organ within the primary beam, SCR was +12% (0%, -12%) for 6-MV and +5% (-2%, -7%) for 18-MV IMRT. 18-MV IMRT increased SCR 6-7 times for organs away from the primary beam relative to 3DCRT and 6-MV IMRT. Skin SCR increased by 22-37% for 6-MV and 50-69% for 18-MV IMRT inasmuch as a larger volume of skin was exposed.

CONCLUSION

Cancer risk after IMRT for cervical and endometrial cancer is dependent on treatment energy. 6-MV pelvic IMRT represents a safe alternative with respect to SCR relative to 3DCRT, independently of the dose-response model. 18-MV IMRT produces second neutrons that modestly increase the SCR.

Conformal and intensity-modulated radiotherapy for cervical cancer

Three-dimensional radiotherapy planning techniques, including conformal radiotherapy and intensity-modulated radiotherapy, have potential for improving outcomes in cervical cancer. Accurate target volume definition is essential in order to maximise normal tissue sparing while minimising the risk of a geographical miss. This reduction in toxicity provides the option of dose escalation, particularly with simultaneous integrated boost intensity-modulated radiotherapy. The evidence for the current use and potential applications of these techniques in the treatment of cervical cancer are discussed.

Dosimetric comparison of helical tomotherapy treatment and step-and-shoot intensity-modulated radiotherapy of retroperitoneal sarcoma

PURPOSE

To compare step-and-shoot intensity-modulated radiation therapy (SAS-IMRT) and helical tomotherapy (Tomo) dosimetry plans for patients who have received adjuvant radiation therapy for retroperitoneal sarcomas (RSTS).

METHODS AND MATERIALS

A retrospective review was performed for seven patients who received either SAS-IMRT or Tomo as adjuvant radiation therapy for RSTS. In each case, a treatment plan of the other modality was generated so that SAS-IMRT and Tomo could be compared.

RESULTS

The average percentage of clinical target volume (CTV) that received less than the prescription dose was 1.4% for Tomo compared to 3.8% for SAS-IMRT. Both SAS-IMRT and Tomo plans provided comparable and significant reductions in volume of small bowel receiving greater than 45 Gy compared to simple opposing standard radiation fields. For the ipsilateral kidney, Tomo significantly reduced the volume of kidney that received at least 15 Gy (average 22% for Tomo vs. 56% for SAS-IMRT).

CONCLUSION

Both SAS-IMRT and Tomo can encompass the large CTV often required for patients with RSTS, although Tomo provides superior dose uniformity. Both SAS-IMRT and Tomo can minimize the volume of small bowel receiving greater than 45 Gy. Tomo was superior to SAS-IMRT in minimizing the volume of ipsilateral kidney irradiated to greater than 15 Gy when the CTV is adjacent to a kidney. Dose escalation and target margin expansion may thus become realistic possibilities.

A dosimetric analysis of dose escalation using two intensity-modulated radiation therapy techniques in locally advanced pancreatic carcinoma

PURPOSE

To perform an analysis of three-dimensional conformal radiation therapy (3D-CRT), sequential boost intensity-modulated radiation therapy (IMRTs), and integrated boost IMRT (IMRTi) for dose escalation in unresectable pancreatic carcinoma.

METHODS AND MATERIALS

Computed tomography images from 15 patients were used. Treatment plans were generated using 3D-CRT, IMRTs, and IMRTi for dose levels of 54, 59.4, and 64.8 Gy. Plans were analyzed for target coverage, doses to liver, kidneys, small bowel, and spinal cord.

RESULTS

Three-dimensional-CRT exceeded tolerance to small bowel in 1 of 15 (6.67%) patients at 54 Gy, and 4 of 15 (26.7%) patients at 59.4 and 64.8 Gy. 3D-CRT exceeded spinal cord tolerance in 1 of 15 patients (6.67%) at 59.4 Gy and liver constraints in 1 of 15 patients (6.67%) at 64.8 Gy; no IMRT plans exceeded tissue tolerance. Both IMRT techniques reduced the percentage of total kidney volume receiving 20 Gy (V20), the percentage of small bowel receiving 45 Gy (V45), and the percentage of liver receiving 35 Gy (V35). IMRTi appeared superior to IMRTs in reducing the total kidney V20 (p < 0.0001), right kidney V20 (p < 0.0001), and small bowel V45 (p = 0.02).

CONCLUSIONS

Sequential boost IMRT and IMRTi improved the ability to achieve normal tissue dose goals compared with 3D-CRT. IMRTi allowed dose escalation to 64.8 Gy with acceptable normal tissue doses and superior dosimetry compared with 3D-CRT and IMRTs.