Comparison of clinical outcomes and toxicity in endometrial cancer patients treated with adjuvant intensity-modulated radiation therapy or conventional radiotherapy

Prospective randomised phase II trial evaluating adjuvant pelvic radiotherapy using either IMRT or 3-Dimensional planning for endometrial cancer

OBJECTIVE

To compare the incidence of grade ≥2 gastrointestinal (GI) or genitourinary (GU) toxicity for patients undergoing 3DRT versus IMRT in the postoperative setting for endometrial cancer.

METHODS

Eligible patients were post-operatively randomly assigned to one of two parallel groups in a 1:1 ratio, to have their RT delivered using either a 3DRT technique or using IMRT. The prescription dose was 45 Gy in 25 fractions over 5 weeks followed by vaginal vault brachytherapy. Toxicity was graded according to National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version (v) 3.0. Fisher's exact tests were used to test for associations between toxicity and arm. Differences in dosimetric parameters for patients with or without toxicity were tested using Mann-Whitney U-tests.

RESULTS

84 patients with a median age of 62 were evaluable for primary outcome. The median follow-up was 52 months. 14 (35%) participants from the 3DRT arm and 15 (34%) from the IMRT arm experienced acute grade ≥2 GI toxicity with older patients having a statistically higher risk of grade ≥2 acute GI toxicity. 20 (50%) participants from the 3DRT arm and 25 (57%) from the IMRT arm experienced acute grade ≥2 GI or GU toxicity (p = .662). 12 (30%) patients from the 3DRT arm and 17 (39%) from the IMRT arm experienced acute grade ≥2 GU toxicity (p = .493).

CONCLUSION

Although IMRT can reduce dose to normal tissue, in this study no benefit in acute GI or GU toxicity outcome was seen.

Outcome and safety analysis of endometrial cancer patients treated with postoperative 3D-conformal radiotherapy or intensity modulated radiotherapy

BACKGROUND

We sought to analyze the toxicity rates and the treatment outcomes in endometrial cancer (EC) patients treated with postoperative three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT).

MATERIAL AND METHODS

The clinical data of 646 EC patients treated with postoperative adjuvant 3DCRT (265 patients, 41%) or with IMRT (381 patients, 59%) between April 2007 and August 2019 were retrospectively analyzed. The primary endpoints were treatment-related acute and late gastrointestinal (GI) and genitourinary (GU) toxicities. The secondary endpoints were LC and overall survival (OS) and disease-free survival (DFS).

RESULTS

Median follow-up time was 37 months. The rates for acute GI and GU toxicities of any grade for the entire group were 55.6% and 46.8%, respectively. Acute grade ≥2 GI toxicity was significantly less in patients treated with IMRT compared to those treated with 3DCRT (11.0% vs. 19.2%, p=.004). However, no significant difference grade ≥2 GU toxicities was observed between the 3DCRT and IMRT groups (15.1% vs. 11.0%; p=.15). Acute grade ≥2 GI and GU toxicities were higher in patients receiving systemic chemotherapy, while paraaortic field irradiation increases only the risk of acute grade ≥2 GI toxicity. Estimated 3-year late grade ≥3 GI toxicity rates in the 3DCRT- and IMRT-treated patients were 4.6% and 1.9% (p= .03), respectively. The patients treated with adjuvant ChT had higher rates of late serious GI complications than those without adjuvant ChT. No significant difference in terms of survival and disease control was observed between the 3DCRT and IMRT treatment groups. No significant factor for LC was found in the multivariate analysis.

CONCLUSION

In this multicentric study involving one of largest patient population, we found that IMRT-treated EC patients showed comparable clinical outcomes but with a lower incidence of GI toxicities compared with those treated with 3DCRT.

Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron

Microbeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G4SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths.

Increased risk for second primary rectal cancer after pelvic radiation therapy

BACKGROUND

The aim of this study was to analyse the association between pelvic radiation therapy (RT) and the development of rectal cancer as a second primary cancer.

METHODS

Data on patients treated for a primary pelvic cancer between 1989 and 2007 were retrieved from the population-based Netherlands Cancer Registry. Patients treated for more than one pelvic cancer were excluded. To estimate the cumulative incidence of rectal cancer, Fine and Gray's competing risk model was used with death as a competing event. Survival was calculated using multivariable Cox regression.

RESULTS

A total of 192,658 patients were included, of which 62,630 patients were treated with RT for their pelvic cancer. Primary tumours were located in the prostate (50.1%), bladder (19.2%), endometrium (13.9%), ovaries (10.0%), cervix (6.4%) and vagina (0.4%). At a median interval of 6 years (range 0-24), 1369 patients developed a rectal cancer. Overall, the risk for rectal cancer was increased in patients who underwent RT for the previous pelvic cancer (subhazard ratio [SHR]: 1.72, 95% confidence interval [CI]: 1.55-1.91). Analysis for each tumour location specifically showed an increased risk in patients who received RT for prostate (SHR: 1.89, 95% CI: 1.66-2.16) or endometrial cancer (SHR: 1.50, 95% CI: 1.13-2.00). A protective effect of RT was observed for patients with bladder cancer (SHR 0.67, 95% CI: 0.47-0.94). There was no survival difference between patients with rectal cancer with or without previous RT (hazard ratio: 0.94, 95% CI: 0.79-1.11).

CONCLUSIONS

Patients who received RT for a previous pelvic cancer were at increased risk for rectal cancer. The risk was modest and pronounced in patients receiving RT for prostate and endometrial cancer.

Comparison of 3D conformal radiation therapy and intensity-modulated radiation therapy in patients with endometrial cancer: efficacy, safety and prognostic analysis

Introduction: Adjuvant whole-pelvic radiation therapy (WPRT) improves locoregional control for high-intermediate stages I-III endometrial cancer patients. Intensity modulated radiation therapy (IMRT) tends to replace the standard 3D conformal radiation therapy (3DCRT) technique used in trials. Material and methods: Consecutive patients with stages I-IIIc endometrial cancer treated between 2008 and 2014 in our department with post-operative 3DCRT or IMRT WPRT were studied retrospectively. Patients with cervical involvement underwent additional low-dose rate vaginal brachytherapy. The impact of the WPRT technique on local control, tolerance, disease-free survival (DFS) and overall survival (OS) was assessed. Clinicians evaluated routinely acute radiation toxicity each week during radiation therapy and late toxicity during standard follow-up consultations. Results: Median follow-up was 50 months (range: 6-158). Among the 83 patients included, 47 were treated with 3DCRT and 36 with IMRT. There was no difference in patient characteristics between groups. The 5-year locoregional control and DFS rates were 94.5% and 68%, respectively. No significant difference was found between the 3DCRT and IMRT groups in terms of survival, with 5-year OS rates of 74.6% and 78%, respectively. In multivariate analysis, age over 68, stage > T1 and grade 3 were independently associated with shorter DFS and OS. Seven patients (8.4%) had grades 3-4 acute gastrointestinal (GI) toxicity with five patients (10.6%) and two (5.4%) in the 3DCRT and IMRT groups, respectively (p = .69). One case (1.2%) of late grade 3 GI toxicity was observed treated in 3DCRT. Conclusions: IMRT seems to be a safe technique for the treatment of endometrial cancer with a trend towards decreased acute GI toxicities. Results of the phase 3 RTOG 1203 trial are needed to confirm these results.

Proton Therapy Reduces Normal Tissue Dose in Extended-Field Pelvic Radiation for Endometrial Cancer

PURPOSE

We dosimetrically compared pencil beam scanning (PBS) proton therapy and intensity-modulated radiation therapy (IMRT) for pelvic and para-aortic lymph node disease in endometrial carcinoma and present acute toxicities associated with extended-field PBS.

PATIENTS AND METHODS

Twenty-five patients with locally advanced endometrial malignancies were enrolled in an image-guided registry study. Seven of these patients were treated with PBS, and 18 patients were treated with IMRT. Organs at risk included pelvic bone marrow (PBM), small bowel (SB), large bowel (LB), rectum, bladder, and kidneys. The IMRT and PBS dosimetric parameters were compared using Wilcoxon rank-sum tests.

RESULTS

Compared with IMRT PBM dose-volume histograms, PBS resulted in significantly lower dose volumes from 0 to 26.0 Gy (P < .05) and higher dose volumes from 33.9 to 42.9 Gy (P < .05). Overall, PBS resulted in 22% lower median PBM volume irradiated to 10 Gy (RBE) (PBS 71.3% versus IMRT 93.4%, P < .001) and 14% lower median volume irradiated to 20 Gy (RBE) (PBS 65.1% versus IMRT 79.4%, P < .001). Compared with IMRT, PBS also significantly reduced SB dose volumes from 0 to 27.5 Gy, LB dose volumes from 0 to 31.6 Gy, bladder dose volumes from 0 to 27.3 Gy, and rectal dose volumes from 0 to 7.6 Gy (all P < .05). However, PBS resulted in higher rectal dose volumes compared with IMRT from 26.0 to 48.4 Gy. Grade 3+ hematologic toxicities were present in 2 (11%) IMRT-treated patients and no PBS-treated patients. No grade 3+ gastrointestinal or genitourinary toxicities were present in either treatment group.

CONCLUSION

In endometrial carcinoma, extended-field PBS is clinically feasible, resulting in statistically significant dose reduction to PBM as well as SB, LB, and bladder in the lower dose regions.

[Doses to organs at risk for conformational and stereotactic radiotherapy: Bladder]

Bladder dose constraints in case of conformational radiotherapy/intensity-modulated radiotherapy and stereotactic radiotherapy are reported from the literature, in particular from the French radiotherapy society RECORAD recommendations, according to the treated pelvic tumor sites. The dose-volume effect on urinary toxicity is not clearly demonstrated, making difficult to establish absolute dose constraints for the bladder. In case of high-dose prostate cancer radiotherapy, the bladder dose constraints are: V60Gy<50% and maximum dose<80Gy for standard fractionation and V60Gy<5%, V48Gy<25% and V41Gy<50% for moderate hypofractionation (20 fractions of 3Gy). In case of prostate stereotactic radiotherapy (five fractions of 7.25Gy), the most frequent dose constraints in the literature are V37Gy<10cm³ and V18Gy<40%. In case of conformational radiotherapy of cervix cancer, postoperative endometrium, anal canal and rectum, the recommendations are V40Gy<40% and D2% lower than the prescribed dose.

Para-aortic and pelvic extended-field radiotherapy for advanced-stage uterine cancer: dosimetric and toxicity comparison between the four-field box and intensity-modulated techniques

BACKGROUND

In patients with advanced-stage endometrial carcinoma (eca), extended-field radiotherapy (efrt) is traditionally delivered by the 3-dimensional conformal (3d-crt) 4-field box technique. In recent years, the use of intensity-modulated radiotherapy (imrt) in gynecologic cancers has increased. We compared the delivery of efrt by the 3d-crt and contemporary imrt techniques.

METHODS

After surgical staging and adjuvant chemotherapy in 38 eca patients, efrt was delivered by either imrt or 3d-crt. Doses to the organs at risk, side effects, and outcomes were compared between the techniques.

RESULTS

Of the 38 eca patients, 33 were stage iiic, and 5 were stage ivb. In the imrt group, maximal doses to rectum, small intestine, and bladder were significantly higher, and mean dose to bladder was lower (p < 0.0001). Most acute gastrointestinal, genitourinary, and hematologic side effects were grade i or ii and were comparable between the groups. In long-term follow-up, only grade 1 cystitis at 3 months was statistically higher in the imrt patients. No grade iii or iv gastrointestinal or genitourinary toxicities were observed. No statistically significant differences in overall and disease-free survival or recurrence rates were observed between the techniques.

CONCLUSIONS

In advanced eca patients, imrt is a safe and effective technique for delivering efrt to the pelvis and para-aortic region, and it is comparable to the 3d-crt 4-field box technique in both side effects and efficacy. For centres in which imrt is not readily available, 3d-crt is a valid alternative.