Moderate Hypofractionation with Simultaneous Integrated Boost in Prostate Cancer: Long-term Results of a Phase I-II Study

AIMS

To report 5 year outcome and late toxicity in prostate cancer patients treated with image-guided tomotherapy with a moderate hypofractionated simultaneous integrated boost approach.

MATERIALS AND METHODS

In total, 211 prostate cancer patients, 78 low risk, 53 intermediate risk and 80 high risk were treated between 2005 and 2011. Intermediate- and high-risk patients received 51.8 Gy to pelvic lymph nodes and concomitant simultaneous integrated boost to prostate up to 74.2 Gy/28 fractions, whereas low-risk patients were treated to the prostate only with 71.4 Gy/28 fractions. Daily megavoltage computed tomography (MVCT) image guidance was applied. Androgen deprivation was prescribed for a median duration of 6 months for low-risk patients (for downsizing), 12 months for intermediate-risk and 36 months for high-risk patients. The 5 year biochemical relapse-free survival (bRFS), cancer-specific survival (CSS), overall survival and late gastrointestinal and genitourinary CTCAE.v3 toxicity were assessed. The effect of several clinical variables on both outcome and gastrointestinal/genitourinary toxicity was tested by uni- and multivariate Cox regression analyses.

RESULTS

After a median follow-up of 5 years, the late toxicity actuarial incidence was: genitourinary ≥ grade 2: 20.2%; genitourinary ≥ grade 3: 5.9%; gastrointestinal ≥ grade 2: 17%; gastrointestinal ≥ grade 3: 6.3% with lower prevalence at the last follow-up visit (≥ grade 3: genitourinary: 1.9%; gastrointestinal: 1.9%). Major predictors of ≥ grade 3 genitourinary and gastrointestinal late toxicity were genitourinary acute toxicity ≥ grade 2 (hazard ratio: 4.9) and previous surgery (hazard ratio: 3.4). The overall 5 year bRFS was 93.7% (low risk: 94.6%; intermediate risk: 96.2%; high risk: 91.1%), overall survival and CSS were 88.6% (low risk: 90.5%; intermediate risk: 87.4%; high risk: 87%) and 97.5% (low risk: 98.7%; intermediate risk: 95%; high risk: 94.3%), respectively. Risk classes and androgen deprivation were not significantly correlated with either bRFS, overall survival or CSS. Twelve patients experienced a biochemical relapse but none experienced clinically proven local and/or pelvic recurrence.

CONCLUSION

A satisfactory 5 year outcome with an acceptable toxicity profile was observed. The combination of image-guided radiotherapy-intensity-modulated radiotherapy, high equivalent 2 Gy dose (EQD2) with a moderate hypofractionated approach and extensive prophylactic lymph node irradiation also leads to very good outcome in high-risk patients.

Modeling severe late rectal bleeding: Results on a large pooled population of prostate cancer patients

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Background: To develop a model for grade 3 (G3) late rectal bleeding (LRB) after radical radiotherapy (RT) for prostate cancer, in a pooled population from 2 large prospective trials: Airopros0102 (Fellin RO2014) and TROG 03.04 RADAR (Ebert IJROBP2015). Methods: Both trials included patients (pts) treated with 3DCRT at 66-80Gy, conventional fractionation. Planning data were available for all pts, G3 LRB was prospectively scored using the SOMA/LENT, with a minimum follow-up of 3 years. Rectal dose-volume histograms were reduced to Equivalent Uniform Dose (EUD) calculated with volume parameter n derived by 3 studies: n=0.06 (Rancati RO2004), n=0.05 (Rancati RO2011) and n=0.018 (Defraene IJROBP2011). EUD was inserted into multivariable logistic regression (MVL) together with clinical and treatment features. Irradiation of seminal vesicles (SV), irradiation of pelvic nodes, hormonal therapy, hypertension, previous abdominal surgery (SURG), use of anticoagulants, diabetes, cardiovascular diseases and presence of acute toxicity were considered as potential dose-modifying factors. Goodness of fit was evaluated with Hosmer Lemeshow test (HL), calibration through calibration slope and AUC was used for discrimination power. Results: 1,337 pts were available: 708 RADAR and 669 Airopros. G3 LRB was scored in 95 pts (7.1%): 62 RADAR and 33 Airopros. EUD calculated with n=0.05 was the best dosimetric predictor for G3 LRB. A 4-variable MVL model was fitted including EUD (OR=1.07 p=0.16), SV (OR=4.75 p<0.001), SURG (OR=2.30 p=0.02) and cardiovascular disease (OR=1.42 p=0.18). AUC=0.63, calibration slope=0.99 (R^2=0.89), p for HL=0.43. Inclusion of acute toxicity (OR=2.34 p<0.001) slightly improved AUC (0.65), confirming a possible role of consequential injury. Conclusions: EUD with n=0.05 was predictive of G3 LRB in this pooled population, confirming the importance of sparing the rectum from high doses. Irradiation of seminal vesicles together with the presence of cardiovascular disease and previous abdominal surgery were relevant dose-modifying factors highly impacting the incidence of G3 LRB. The study was funded by: AIRC IG16087, Fondazione Monzino, NHMRC (300705, 455521, 1006447)

Analysis of serial CT images for studying the RT effects in head-neck cancer patients

Images taken during and after RT for head and neck cancer have the potential to quantitatively assess xerostomia. Image information may be used as biomarkers of RT effects on parotid glands with significant potential to support adaptive treatment strategies. We investigated the possibility to extract information based on in-room CT images (kVCT, MVCT), acquired for daily image-guided radiotherapy treatment of head-and-neck cancer patients, in order to predict individual response in terms of toxicity. Follow-up MRI images were also used in order to investigate long term parotid gland deformation.

Dose-volume effects for pelvic bone marrow in predicting hematological toxicity in prostate cancer radiotherapy with pelvic node irradiation

PURPOSE

To prospectively identify clinical/dosimetric predictors of acute/late hematologic toxicity (HT) in chemo-naÏve patients treated with whole-pelvis radiotherapy (WPRT) for prostate cancer.

MATERIAL AND METHODS

Data of 121 patients treated with adjuvant/salvage WPRT were analyzed (static-field IMRT n=19; VMAT/Rapidarc n=57; Tomotherapy n=45). Pelvic bone marrow (BM) was delineated as ilium (IL), lumbosacral, lower and whole pelvis (WP), and the relative DVHs were calculated. HT was graded both according to CTCAE v4.03 and as variation in percentage relative to baseline. Logistic regression was used to analyze association between HT and clinical/DVHs factors.

RESULTS

Significant differences (p<0.005) in the DVH of BM volumes between different techniques were found: Tomotherapy was associated with larger volumes receiving low doses (3-20 Gy) and smaller receiving 40-50 Gy. Lower baseline absolute values of WBC, neutrophils and lymphocytes (ALC) predicted acute/late HT (p ⩽ 0.001). Higher BM V40 was associated with higher risk of acute Grade3 (OR=1.018) or late Grade2 lymphopenia (OR=1.005). Two models predicting lymphopenia were developed, both including baseline ALC, and BM WP-V40 (AUC=0.73) and IL-V40+smoking (AUC=0.904) for acute/late respectively.

CONCLUSIONS

Specific regions of pelvic BM predicting acute/late lymphopenia, a risk factor for viral infections, were identified. The 2-variable models including specific constraints to BM may help reduce HT.

Second Tumor Induction Risk in IMRT for Prostate Cancer: An Unbalanced Comparison Between Surgery and Radiotherapy?

The aim of this study was to evaluate the risk of second tumor induction for prostate patients treated with volumetric modulated arc therapy in age classes 50-70. Based on both age-dependent models and doses to critical organs, the risk of second tumor induction was evaluated simulating the small field (prostate and seminal vesicles) and large field (whole pelvis) for Helical Tomotherapy and Rapid Arc. The doses to the organs closest to the treatment volume were derived from treatment planning system data. Whereas, due to the lack of calculation algorithms where leakage and internal radiation scattering are unreliable at a large distance from target, the doses to the organs outside the treatment volume were measured in an anthropomorphic phantom. Doses from Image Guided Radiotherapy (IGRT) were also assessed on phantom measurements. The Lifetime Attributable Risk (LAR) for second tumor induction increases from 2.2 to 13.7% as irradiated volume increases and age decreases. IGRT could add a non-negligible factor to the risk when daily set-up verification with high-resolution modality is included. As prostate cancer is detected earlier, the probability of an increase in early stage patients rises, and life expectancy thus increases. Radiotherapy has improved its capability in the tailoring of the dose around the target at the cost of a greater dose to surrounding organs, thus increasing the risk of second tumor induction, especially for those patients expected to survive 15 y or more.