Acute toxicity of whole-pelvis IMRT in 87 patients with localized prostate cancer

Retrospective study comparing MR-guided radiation therapy (MRgRT) setup strategies for prostate treatment: repositioning vs. replanning

BACKGROUND

This study compared adaptive replanning and repositioning corrections based on soft-tissue matching for prostate cancer by using the magnetic resonance-guided radiation therapy (MRgRT) system.

METHODS

A total of 19 patients with prostate cancer were selected retrospectively. Weekly magnetic resonance image (MRI) scans were acquired for 5 weeks for each patient to observe the anatomic changes during the treatment course. Initial intensity-modulated radiation therapy (IMRT) plans (iIMRT) were generated for each patient with 13 coplanar ⁶⁰Co beams on a ViewRay™ system. Two techniques were applied: patient repositioning and replanning. For patient repositioning, one plan was created: soft-tissue (prostate) matching (Soft). The dose distribution was calculated for each MRI with the beam delivery parameters from the initial IMRT plan. The replanning technique was used to generate the Adaptive plan, which was the reoptimized plan for the weekly MRI. The dose-volumetric parameters of the planning target volume (PTV), bladder, and rectum were calculated for all plans. During the treatment course, the PTV, bladder, and rectum were evaluated for changes in volume and the effect on dosimetric parameters. The differences between the dose-volumetric parameters of the plans were examined through the Wilcoxon test. The initial plan was used as a baseline to compare the differences.

RESULTS

The Adaptive plan showed better target coverage during the treatment period, but the change was not significant in the Soft plan. There were significant differences in D_98%, D_95%, and D_2% in PTV between the Soft and Adaptive plans (p < 0.05) except for D_mean. There was no significant change in D_max and D_mean as the treatment progressed with all plans. All indices for the Adaptive plan stayed the same compared to those of iIMRT during the treatment course. There were significant differences in D_15%, D_25%, D_35%, and D_50% in the bladder between the Soft and Adaptive plans. The Adaptive plan showed the worse dose sparing than the Soft plan for the bladder according to each dosimetric index. In contrast to the bladder, the Adaptive plan achieved better sparing than the Soft plan during the treatment course. The significant differences were only observed in D_15% and D_35% between the Soft and Adaptive plans (p < 0.05).

CONCLUSIONS

Patient repositioning based on the target volume (Soft plan) can relatively retain the target coverage for patients and the OARs remain at a clinically tolerance level during the treatment course. The Adaptive plan did not clinically improve for the dose delivered to OARs, it kept the dose delivered to the target volume constant. However, the Adaptive plan is beneficial when the organ positions and volumes change considerable during treatment.

Probiotics for the prevention or treatment of chemotherapy- or radiotherapy-related diarrhoea in people with cancer

BACKGROUND

Treament-related diarrhoea is one of the most common and troublesome adverse effects related to chemotherapy or radiotherapy in people with cancer. Its reported incidence has been as high as 50% to 80%. Severe treatment-related diarrhoea can lead to fluid and electrolyte losses and nutritional deficiencies and could adversely affect quality of life (QoL). It is also associated with increased risk of infection in people with neutropenia due to anticancer therapy and often leads to treatment delays, dose reductions, or treatment discontinuation. Probiotics may be effective in preventing or treating chemotherapy- or radiotherapy-induced diarrhoea.

OBJECTIVES

To evaluate the clinical effectiveness and side effects of probiotics used alone or combined with other agents for prevention or treatment of chemotherapy- or radiotherapy-related diarrhoea in people with cancer.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 7), MEDLINE (1946 to July week 2, 2017), and Embase (1980 to 2017, week 30). We also searched prospective clinical trial registers and the reference lists of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) investigating the effects of probiotics for prevention or treatment of chemotherapy- or radiotherapy-related diarrhoea in people with cancer.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, extracted data, and assessed risk of bias. We used random-effects models for all meta-analyses. If meta-analysis was not possible, we summarised the results narratively.

MAIN RESULTS

We included 12 studies involving 1554 participants. Eleven studies were prevention studies, of which seven compared probiotics with placebo (887 participants), one compared two doses of probiotics with each other and with placebo (246 participants), and three compared probiotics with another active agent (216 participants).The remaining study assessed the effectiveness of probiotics compared with placebo for treatment of radiotherapy-related diarrhoea (205 participants).For prevention of radiotherapy (with or without chemotherapy)-induced diarrhoea, review authors identified five heterogeneous placebo-controlled studies (with 926 participants analysed). Owing to heterogeneity, we could not carry out a meta-analysis, except for two outcomes. For occurrence of any diarrhoea, risk ratios (RRs) ranged from 0.35 (95% confidence interval (CI) 0.26 to 0.47) to 1.0 (95% CI 0.94 to 1.06) (three studies; low-certainty evidence). A beneficial effect of probiotics on quality of life could neither be demonstrated nor refuted (two studies; low-certainty evidence). For occurrence of grade 2 or higher diarrhoea, the pooled RR was 0.75 (95% CI 0.55 to 1.03; four studies; 420 participants; low-certainty evidence), and for grade 3 or higher diarrhoea, RRs ranged from 0.11 (95% CI 0.06 to 0.23) to 1.24 (95% CI 0.74 to 2.08) (three studies; low-certainty evidence). For probiotic users, time to rescue medication was 36 hours longer in one study (95% CI 34.7 to 37.3), but another study reported no difference (moderate-certainty evidence). For the need for rescue medication, the pooled RR was 0.50 (95% CI 0.15 to 1.66; three studies; 194 participants; very low-certainty evidence). No study reported major differences between groups with respect to adverse effects. Although not mentioned explicitly, no studies reported deaths, except one in which one participant in the probiotics group died of myocardial infarction after three sessions of radiotherapy.Three placebo-controlled studies, with 128 analysed participants, addressed prevention of chemotherapy-induced diarrhoea. For occurrence of any diarrhoea, the pooled RR was 0.59 (95% CI 0.36 to 0.96; two studies; 106 participants; low-certainty evidence). For all other outcomes, a beneficial effect of probiotics could be neither demonstrated nor refuted (one to two studies; 46 to 106 participants; all low-certainty evidence). Studies did not address quality of life nor time to rescue medication.Three studies compared probiotics with another intervention in 213 participants treated with radiotherapy (with or without chemotherapy). One very small study (21 participants) reported less diarrhoea six weeks after treatment when dietary counselling was provided (RR 0.30, 95% CI 0.11 to 0.81; very low-certainty evidence). In another study (148 participants), grade 3 or 4 diarrhoea occurred less often in the probiotics group than in the control group (guar gum containing nutritional supplement) (odds ratio (OR) 0.38, 95% CI 0.16 to 0.89; low-certainty evidence), and two studies (63 participants) found less need for rescue medication of probiotics versus another active treatment (RR 0.44, 95% CI 0.22 to 0.86; very low-certainty evidence). Studies did not address quality of life nor time to rescue medication.One placebo-controlled study with 205 participants addressed treatment for radiotherapy-induced diarrhoea and could not demonstrate or refute a beneficial effect of probiotics on average diarrhoea grade, time to rescue medication for diarrhoea (13 hours longer in the probiotics group; 95% CI -0.9 to 26.9 hours), or need for rescue medication (RR 0.74, 95% CI 0.53 to 1.03; moderate-certainty evidence). This study did not address quality of life.No studies reported serious adverse events or diarrhoea-related deaths.

AUTHORS' CONCLUSIONS

This review presents limited low- or very low-certainty evidence supporting the effects of probiotics for prevention and treatment of diarrhoea related to radiotherapy (with or without chemotherapy) or chemotherapy alone, need for rescue medication, or occurrence of adverse events. All studies were underpowered and heterogeneous. Severe side effects were absent from all studies.Robust evidence on this topic must be provided by future methodologically well-designed trials.

Minimal toxicity after proton beam therapy for prostate and pelvic nodal irradiation: results from the proton collaborative group REG001-09 trial

BACKGROUND

Proton beam therapy (PBT) reduces normal organ dose compared to intensity modulated radiation therapy (IMXT) for prostate cancer patients who receive pelvic radiation therapy. It is not known whether this dosimetric advantage results in less gastrointestinal (GI) and genitourinary (GU) toxicity than would be expected from IMXT.

MATERIAL AND METHODS

We evaluated treatment parameters and toxicity outcomes for non-metastatic prostate cancer patients who received pelvic radiation therapy and enrolled on the PCG REG001-09 trial. Patients who received X-ray therapy and/or brachytherapy were excluded. Of 3210 total enrolled prostate cancer patients, 85 received prostate and pelvic radiation therapy exclusively with PBT. Most had clinically and radiographically negative lymph nodes although 6 had pelvic nodal disease and one also had para-aortic involvement. Pelvic radiation therapy was delivered using either 2 fields (opposed laterals) or 3 fields (opposed laterals and a posterior beam). Median pelvic dose was 46.9 GyE (range 39.7-56) in 25 fractions (range 24-30). Median boost dose to the prostate +/- seminal vesicles was 30 GyE (range 20-41.4) in 16 fractions (range 10-24).

RESULTS

Median follow-up was 14.5 months (range 2.8-49.2). Acute grade 1, 2, and 3 GI toxicity rates were 16.4, 2.4, 0%, respectively. Acute grade 1, 2, and 3 GU toxicity rates were 60, 34.1, 0%, respectively.

CONCLUSIONS

Prostate cancer patients who receive pelvic radiation therapy using PBT experience significantly less acute GI toxicity than is expected using IMXT. Further investigation is warranted to confirm whether this favorable acute GI toxicity profile is related to small bowel sparing from PBT.

[Clinical to planning target volume margins in prostate cancer radiotherapy]

The knowledge of inter- and intrafraction motion and deformations of the intrapelvic target volumes (prostate, seminal vesicles, prostatectomy bed and lymph nodes) as well as the main organs at risk (bladder and rectum) allow to define rational clinical to planning target volume margins, depending on the different radiotherapy techniques and their uncertainties. In case of image-guided radiotherapy, prostate margins and seminal vesicles margins can be between 5 and 10mm. The margins around the prostatectomy bed vary from 10 to 15mm and those around the lymph node clinical target volume between 7 and 10mm. Stereotactic body radiotherapy allows lower margins, which are 3 to 5mm around the prostate. Image-guided and stereotactic body radiotherapy with adequate margins allow finally moderate or extreme hypofractionation.

Comparison of dosimetric parameters and acute toxicity after whole-pelvic vs prostate-only volumetric-modulated arc therapy with daily image guidance for prostate cancer

OBJECTIVE

To compare dosimetric parameters and acute toxicity rates between whole-pelvic (WP) and prostate-only (PO) volumetric-modulated arc therapy (VMAT) in patients with localized prostate cancer.

METHODS

A total of 224 consecutive patients treated with definitive VMAT to 78 Gy in 39 fractions were enrolled. Of these, 119 patients received initial WP VMAT at 46.8 Gy in 26 fractions using a simultaneous integrated boost technique, and 105 patients received PO VMAT. Image-guided radiotherapy was practised with daily cone beam CT.

RESULTS

The mean rectal dose, the rectal volume receiving ≥30 Gy (V30Gy), rectal V50Gy, the mean bladder dose, bladder V30Gy and bladder V50Gy were significantly increased in the WP group (p < 0.05 each); however, the rectal V70Gy did not differ between groups (p = 0.101), and the bladder V70Gy was significantly lower in the WP group (p = 0.029). The WP group experienced a significantly increased frequency of acute grade 2 diarrhoea relative to the PO group (5.9% vs 0%; p = 0.015). No differences were seen between the WP and PO groups in terms of acute grade 2 proctitis (10.1% vs 6.7%; p = 0.360) and genitourinary (GU) toxicity (12.6% vs 10.5%; p = 0.620).

CONCLUSION

Despite larger rectum and bladder volumes at low- and medium-dose levels, WP VMAT resulted in no significant increase in acute proctitis or GU toxicity when compared with PO VMAT.

ADVANCES IN KNOWLEDGE

This study demonstrates that whole-pelvic radiotherapy has comparable acute toxicity to those observed with prostate-only radiotherapy when VMAT with daily image guidance is used.

Acute anal toxicity after whole pelvic radiotherapy in patients with asymptomatic haemorrhoids: identification of dosimetric and patient factors

OBJECTIVE

Patients with asymptomatic haemorrhoids are known to be less tolerant of radiation doses lower than known tolerance doses. In the present study, the authors sought to identify the risk factors of acute haemorrhoid aggravation after whole pelvic radiotherapy (WPRT).

METHODS

The records of 33 patients with cervical, rectal or prostate cancer with asymptomatic haemorrhoids, which were confirmed by colonoscopy before the start of radiotherapy (RT), were reviewed. Acute anal symptoms, such as anal pain and bleeding, were observed up to 1 month after RT completion. Dosimetric and patient factors were analysed, and subgroup analyses were performed.

RESULTS

The median induction dose for acute anal symptoms was 34.1 Gy (range, 28.8-50.4 Gy). Post-operative treatment intent showed more acute anal toxicity of patient factors (p = 0.04). In subgroup analysis, post-operative treatment intent and concurrent chemoradiotherapy were found to be related to acute anal symptoms (p < 0.01). Of the dosimetric factors, V10 tended to be related to acute anal symptoms (p = 0.08).

CONCLUSION

This study indicates that asymptomatic haemorrhoid may deteriorate after low-dose radiation and that patient factors, such as treatment intent and concurrent chemotherapy, probably influence anal toxicity. In patients with asymptomatic haemorrhoids, WPRT requires careful dosimetry and clinical attention.

ADVANCES IN KNOWLEDGE

The tolerance of anal canal tends to be ignored in patients with pelvic cancer who are undergoing WPRT. However, patients with asymptomatic haemorrhoids may be troubled by low radiation doses, and further studies are required.

Whole-pelvic volumetric-modulated arc therapy for high-risk prostate cancer: treatment planning and acute toxicity

The objectives of this study were to evaluate dosimetric quality and acute toxicity of volumetric-modulated arc therapy (VMAT) and daily image guidance in high-risk prostate cancer patients. A total of 100 consecutive high-risk prostate cancer patients treated with definitive VMAT with prophylactic whole-pelvic radiotherapy (WPRT) were enrolled. All patients were treated with a double-arc VMAT plan delivering 52 Gy to the prostate planning target volume (PTV), while simultaneously delivering 46.8 Gy to the pelvic nodal PTV in 26 fractions, followed by a single-arc VMAT plan delivering 26 Gy to the prostate PTV in 13 fractions. Image-guided RT was performed with daily cone-beam computed tomography. Dose-volume parameters for the PTV and the organs at risk (OARs), total number of monitor units (MUs) and treatment time were evaluated. Acute toxicity was assessed using the Common Terminology Criteria for Adverse Events, version 4.0. All dosimetric parameters met the present plan acceptance criteria. Mean MU and treatment time were 471 and 146 s for double-arc VMAT, respectively, and were 520 and 76 s for single-arc VMAT, respectively. No Grade 3 or higher acute toxicity was reported. Acute Grade 2 proctitis, diarrhea, and genitourinary toxicity occurred in 12 patients (12%), 6 patients (6%) and 13 patients (13%), respectively. The present study demonstrated that VMAT for WPRT in prostate cancer results in favorable PTV coverage and OAR sparing with short treatment time and an acceptable rate of acute toxicity. These findings support the use of VMAT for delivering WPRT to high-risk prostate cancer patients.

Image guided intensity modulated hypofractionated radiotherapy in high-risk prostate cancer patients treated four or five times per week: analysis of toxicity and preliminary results

Background

To evaluate efficacy and toxicity of hypofractionated intensity-modulated simultaneous integrated boost (IMRT-SIB) and image-guided (IGRT) radiotherapy in the treatment of high-risk prostate cancer patients.

Methods

Eighty-two patients with high-risk prostate cancer were analysed. An IMRT treatment was planned delivering 68.75 Gy to the prostate, 55 Gy to the seminal vesicles and positive nodes and 45 Gy to the pelvis in 25 fractions. The first 59 patients received 4 weekly fractions whereas the last 23 patients received 5 weekly fractions. All patients were submitted to hormonal therapy.

Results

The median follow-up was 31 months. Acute grade 1–2 gastrointestinal (GI) toxicity rates were 13.4%. Grade 1–2 and grade 3 genitourinary (GU) toxicity rates were 22% and 1.2%, respectively.

Grade 1 and 2 GI late toxicity rates were 1.2%. No grade ≥3 toxicity was recorded. Grade 1 GU late toxicity rate was 2.4%. No grade ≥2 toxicity was recorded.

No significant difference was calculated in terms of acute and late toxicity between the group treated 4 or 5 times weekly.

The actuarial 3-years Overall survival and Freedom from biochemical failure were 98.6% and 91.3%, respectively.

Conclusions

The present study demonstrated that hypofractionated IGRT-IMRT-SIB in patients with high-risk prostate cancer is efficient with acceptable toxicity profile. Outcome in terms of survival are promising, but longer follow-up is needed.

Feasibility of sorafenib combined with local radiotherapy in advanced hepatocellular carcinoma

PURPOSE

Sorafenib is an effective systemic agent for advanced hepatocellular carcinoma. To increase its efficacy, we evaluated the feasibility and benefit of sorafenib combined with radiotherapy.

MATERIALS AND METHODS

From July 2007 to July 2011, 31 patients were treated with a daily dose of 800 mg of sorafenib and radiotherapy. Among them, 13 patients who received radiotherapy on the bone metastasis were excluded. Thirteen patients received 30-54 Gy of radiotherapy on the primary tumor (primary group) and 5 patients received 30-58.4 Gy on the measurable metastatic lesions (measurable metastasis group). Tumor responses at 1 month after the completion of radiotherapy and overall survival were evaluated.

RESULTS

The in-field response rate was 100% in the primary group and 60% in the measurable metastasis group. A decrease of more than 80% in the tumor marker α-fetoprotein was observed in 7 patients in the primary group (54%). Toxicities of grades 3-4 were hand-foot syndrome in 3 (17%) patients, duodenal bleeding in 1 (6%) patient, thrombocytopenia in 3 (17%) patients and elevation of aspartate transaminase in 1 (6%) patient. The median overall survival was 7.8 months (95% confidence interval, 3.0-12.6).

CONCLUSION

The combined treatment of sorafenib and radiotherapy was feasible and induced substantial tumor responses in the target lesions. The results of this study emphasize the importance of individualized approach in the management of advanced hepatocellular carcinoma and encourage the initiation of a controlled clinical trial.

Proton versus intensity-modulated radiotherapy for prostate cancer: patterns of care and early toxicity

BACKGROUND

Proton radiotherapy (PRT) is an emerging treatment for prostate cancer despite limited knowledge of clinical benefit or potential harms compared with other types of radiotherapy. We therefore compared patterns of PRT use, cost, and early toxicity among Medicare beneficiaries with prostate cancer with those of intensity-modulated radiotherapy (IMRT).

METHODS

We performed a retrospective study of all Medicare beneficiaries aged greater than or equal to 66 years who received PRT or IMRT for prostate cancer during 2008 and/or 2009. We used multivariable logistic regression to identify factors associated with receipt of PRT. To assess toxicity, each PRT patient was matched with two IMRT patients with similar clinical and sociodemographic characteristics. The main outcome measures were receipt of PRT or IMRT, Medicare reimbursement for each treatment, and early genitourinary, gastrointestinal, and other toxicity. All statistical tests were two-sided.

RESULTS

We identified 27,647 men; 553 (2%) received PRT and 27,094 (98%) received IMRT. Patients receiving PRT were younger, healthier, and from more affluent areas than patients receiving IMRT. Median Medicare reimbursement was $32,428 for PRT and $18,575 for IMRT. Although PRT was associated with a statistically significant reduction in genitourinary toxicity at 6 months compared with IMRT (5.9% vs 9.5%; odds ratio [OR] = 0.60, 95% confidence interval [CI] = 0.38 to 0.96, P = .03), at 12 months post-treatment there was no difference in genitourinary toxicity (18.8% vs 17.5%; OR = 1.08, 95% CI = 0.76 to 1.54, P = .66). There was no statistically significant difference in gastrointestinal or other toxicity at 6 months or 12 months post-treatment.

CONCLUSIONS

Although PRT is substantially more costly than IMRT, there was no difference in toxicity in a comprehensive cohort of Medicare beneficiaries with prostate cancer at 12 months post-treatment.

Domestic versus imported octreotide in the treatment of acute diarrhea associated with anti-tumor therapy: an analysis of 138 cases

AIM: To compare the efficacy of domestic and imported octreotide (Sandostatin) in the treatment of acute diarrhea associated with anti-tumor therapy.

METHODS: One hundred and thirty-eight patients with grade II or III diarrhea were enrolled into the study, of which 66 received Sandostatin treatment, and 72 were given domestic octreotide (100 µg, tid). Therapeutic efficacy was evaluated after a 3-day treatment.

RESULTS: No significant difference was noted in the complete remission rate of diarrhea between patients treated with Sandostatin and domestic octreotide (75.8% vs 79.2%, P > 0.05). The doses of domestic octreotide used on days 2 and 3 were significantly higher than those of Sandostatin (both P < 0.05). The cost-effectiveness value for Sandostatin was significantly higher than that for domestic octreotide (1148.7 vs 507.3, P < 0.05).

CONCLUSION: Domestic octreotide has equivalent efficacy and superior cost-effectiveness to Sandostatin in treating acute diarrhea associated with anti-tumor therapy. Increasing the dose of domestic octreotide is a reasonable choice in the management of grade III diarrhea.

Predictors of acute bowel toxicity in patients treated with IMRT whole pelvis irradiation after prostatectomy

PURPOSE/OBJECTIVE

Whole pelvis irradiation with IMRT (WPRT-IMRT) after prostatectomy is efficient in reducing acute toxicity: however, a number of patients still experience moderate acute bowel toxicity.

MATERIALS AND METHODS

Ninety-six patients treated with WPRT-IMRT after prostatectomy with adjuvant or salvage intent were analysed. A number of parameters were individually recovered, including the DVHs of the intestinal cavity outside PTV and of the loops referred to both the WPRT phase and the whole treatment. Correlation between clinical-dosimetric parameters and acute bowel toxicity was investigated by logistic analyses. Best predictive cut-off values for continuous variables were assessed by ROC curves.

RESULTS

15/96 (15.6%) Patients experienced grade 2 toxicity (no grade 3). Best dose-volume predictors were the fraction of loops receiving more than 45, 50 and 55 Gy (respectively, V45TL ≥ 50cc, V50TL ≥ 13cc, V55TL ≥ 3cc; p-values ranging from 0.005 to 0.027). Age, GU acute toxicity, rectal acute toxicity and time between prostatectomy and IMRT were also predictors of acute bowel toxicity. Multivariate analysis showed that the most predictive independent parameters were age (OR: 1.13; 95%CI: 1.02-1.25; p=0.021) and V50TL (≥ 13cc, OR: 8.2; 95%CI: 1.7-40; p=0.009).

CONCLUSIONS

The risk of moderate acute uGI toxicity during WPRT-IMRT for post-operatively treated patients increases with age; the risk is substantially reduced in patients with small overlap between PTV and loops.

Clinical toxicities and dosimetric parameters after whole-pelvis versus prostate-only intensity-modulated radiation therapy for prostate cancer

PURPOSE

To assess whether whole-pelvis (WP) intensity-modulated radiation therapy (IMRT) is associated with increased toxicity compared with prostate-only (PO) IMRT.

METHODS AND MATERIALS

We retrospectively analyzed all patients with prostate cancer undergoing definitive IMRT to 79.2 Gy with concurrent androgen deprivation at our institution from November 2005 to May 2007 with a minimum follow-up of 12 months. Thirty patients received initial WP IMRT to 45 Gy in 1.8-Gy fractions, and thirty patients received PO IMRT. Study patients underwent computed tomography simulation and treatment planning by use of predefined dose constraints. Bladder and rectal dose-volume histograms, maximum genitourinary (GU) and gastrointestinal (GI) Radiation Therapy Oncology Group toxicity grade, and late Grade 2 or greater toxicity-free survival curves were compared between the two groups by use of the Student t test, Fisher exact test, and Kaplan-Meier curve, respectively.

RESULTS

Bladder minimum dose, mean dose, median dose, volume receiving 5 Gy, volume receiving 20 Gy, volume receiving 40 Gy, and volume receiving 45 Gy and rectal minimum dose, median dose, and volume receiving 20 Gy were significantly increased in the WP group (all p values < 0.01). Maximum acute GI toxicity was limited to Grade 2 and was significantly increased in the WP group at 50% vs. 13% the PO group (p = 0.006). With a median follow-up of 24 months (range, 12-35 months), there was no difference in late GI toxicity (p = 0.884) or in acute or late GU toxicity.

CONCLUSIONS

Despite dosimetric differences in the volume of bowel, bladder, and rectum irradiated in the low-dose and median-dose regions, WP IMRT results only in a clinically significant increase in acute GI toxicity, in comparison to PO IMRT, with no difference in GU or late GI toxicity.

Clinical comparative study of dose-volume and equivalent uniform dose based predictions in post radiotherapy acute complications

BACKGROUND

Single points placed on Dose-Volume Histograms (DVHs) for treatment plan acceptance are still widely used compared to the Equivalent Uniform Dose (EUD). The aim of this work is to retrospectively measure and compare the ability of both criteria in correctly predicting two clinical outcomes, RTOG grade 2 acute gastrointestinal (GI) and genitourinary (GU) complications in 137 patients treated for prostate cancer.

MATERIAL AND METHODS

For both complications,the best predictions have been achieved by fitting the EUD parameter and a tolerance dose (for a varying DVH point) by maximization of the Area Under the Receiver Operating Curve (AUROC). A complementary likelihood fitting of the Lyman's Normal Tissue Complication Probability (NTCP) allowed a graphical comparison between expected and observed frequencies, and to derive the associated parameters.

RESULTS AND DISCUSSION

No significant differences were found in the AUROC values obtained by using dose-volume or EUD criteria, but all the results highlighted the role of high doses. Limiting V65 (for grade 2 GI) or V73 (for grade 2 GU) was as predictive as limiting EUD value, with n equal to 0.09 or 0.06 respectively, but in all cases AUROC values were low (< 0.7). Likelihood fitting gave m = 0.195 and TD50=72.5 Gy (fixing n=0.06 for acute GU) and m=0.19 and TD50=66 Gy (fixing n=0.09 for acute GI). Both AUROC and likelihood values revealed a better fit for acute GI than for acute GU. The use of a fractionation correction, new clinical contours or previous risk factors could improve these values.

Dose-volume relationships for acute bowel toxicity in patients treated with pelvic nodal irradiation for prostate cancer

PURPOSE

To find correlation between dose-volume histograms (DVHs) of the intestinal cavity (IC) and moderate-severe acute bowel toxicity in men with prostate cancer treated with pelvic nodal irradiation.

METHODS AND MATERIALS

The study group consisted of 191 patients with localized prostate cancer who underwent whole-pelvis radiotherapy with radical or adjuvant/salvage intent during January 2004 to November 2007. Complete planning/clinical data were available in 175 of these men, 91 of whom were treated with a conventional four-field technique (50.4 Gy, 1.8 Gy/fraction) and 84 of whom were treated with IMRT using conventional Linac (n = 26, 50.4 Gy, 1.8 Gy/fraction) or Helical TomoTherapy (n = 58, 50-54 Gy, 1.8-2 Gy/fraction). The IC outside the planning target volume (PTV) was contoured and the DVH for the first 6 weeks of treatment was recovered in all patients. The correlation between a number of clinical and DVH (V10-V55) variables and toxicity was investigated in univariate and multivariate analyses. The correlation between DVHs for the IC outside the PTV and DVHs for the whole IC was also assessed.

RESULTS

Twenty-two patients experienced toxicity (3/22 in the IMRT/tomotherapy group). Univariate analyses showed a significant correlation between V20-V50 and toxicity (p = 0.0002-0.001), with a higher predictive value observed for V40-V50. Previous prostatectomy (p = 0.066) and abdominal/pelvic surgery (p = 0.12) also correlated with toxicity. Multivariate analysis that included V45, abdominal/pelvic surgery, and prostatectomy showed that the most predictive parameters were V45 (p = 0.002) and abdominal/pelvic surgery (p = 0.05, HR = 2.4)

CONCLUSIONS

Our avoidance IMRT approach drastically reduces the incidence of acute bowel toxicity. V40-V50 of IC and, secondarily, previous abdominal/pelvic surgery were the main predictors of acute bowel toxicity.