Physician- and Patient-Reported Outcomes of the MC1635 Phase 3 Trial of Ultrahypofractionated Versus Moderately Hypofractionated Adjuvant Radiation Therapy After Breast-Conserving Surgery

PURPOSE

Our aim was to report physician- and patient-reported outcomes of patients with localized breast cancer treated with moderate versus ultrahypofractionated whole breast irradiation (WBI) after breast-conserving surgery (BCS).

METHODS AND MATERIALS

Between February 2018 and February 2020, patients with localized breast cancer (pT0-3 pN0-1 M0) were offered participation in a phase 3 randomized clinical trial assessing adjuvant moderate hypofractionation (MHF) to 40 Gy in 15 fractions versus ultrahypofractionation (UHF) to 25 Gy in 5 fractions after BCS, with an optional simultaneously integrated boost. Toxicities, cosmesis, and quality of life were assessed at baseline, end of treatment (EOT), and 3 months, 1 year, 2 years, and 3 years from irradiation using validated metric tools.

RESULTS

One hundred seven patients were randomized to MHF (n = 54) or UHF (n = 53) adjuvant WBI. The median follow-up was 42.8 months. Grade 2 radiation dermatitis was experienced by 4 patients (7.4%) in the MHF arm and 2 patients (3.7%) in the UHF arm at EOT (P = .726). No grade 3 or higher toxicities were observed. Deterioration of cosmesis by physician assessment was observed in 2 (6.7%) patients treated in the UHF arm and 1 (1.9%) patient treated in the MHF arm at EOT (P = .534), whereas at 3 months, only 1 (1.8%) patient treated in the MHF arm demonstrated deterioration of cosmesis (P = .315). At EOT, 91% and 94% of patients reported excellent/good cosmesis among those treated with MHF and UHF regimens, respectively (P = .550). At 3 months, more patients within the MHF arm reported excellent/good cosmesis compared with those in the UHF arm (100% vs 91%; P = .030). However, the difference in patient-reported cosmesis disappeared at the 1-, 2-, and 3-year time points.

CONCLUSIONS

UHF WBI showed similar treatment-related late toxicities and similar provider-scored cosmesis compared with MHF radiation in patients treated adjuvantly after BCS.

Beam mask and sliding window-facilitated deep learning-based accurate and efficient dose prediction for pencil beam scanning proton therapy

BACKGROUND

Accurate and efficient dose calculation is essential for on-line adaptive planning in proton therapy. Deep learning (DL) has shown promising dose prediction results in photon therapy. However, there is a scarcity of DL-based dose prediction methods specifically designed for proton therapy. Successful dose prediction method for proton therapy should account for more challenging dose prediction problems in pencil beam scanning proton therapy (PBSPT) due to its sensitivity to heterogeneities.

PURPOSE

To develop a DL-based PBSPT dose prediction workflow with high accuracy and balanced complexity to support on-line adaptive proton therapy clinical decision and subsequent replanning.

METHODS

PBSPT plans of 103 prostate cancer patients (93 for training and the other 10 for independent testing) and 83 lung cancer patients (73 for training and the other 10 for independent testing) previously treated at our institution were included in the study, each with computed tomography scans (CTs), structure sets, and plan doses calculated by the in-house developed Monte-Carlo dose engine (considered as the ground truth in the model training and testing). For the ablation study, we designed three experiments corresponding to the following three methods: (1) Experiment 1, the conventional region of interest (ROI) (composed of targets and organs-at-risk [OARs]) method. (2) Experiment 2, the beam mask (generated by raytracing of proton beams) method to improve proton dose prediction. (3) Experiment 3, the sliding window method for the model to focus on local details to further improve proton dose prediction. A fully connected 3D-Unet was adopted as the backbone. Dose volume histogram (DVH) indices, 3D Gamma passing rates with a criterion of 3%/3 mm/10%, and dice coefficients for the structures enclosed by the iso-dose lines between the predicted and the ground truth doses were used as the evaluation metrics. The calculation time for each proton dose prediction was recorded to evaluate the method's efficiency.

RESULTS

Compared to the conventional ROI method, the beam mask method improved the agreement of DVH indices for both targets and OARs and the sliding window method further improved the agreement of the DVH indices (for lung cancer, CTV D98 absolute deviation: 0.74 ± 0.18 vs. 0.57 ± 0.21 vs. 0.54 ± 0.15 Gy[RBE], ROI vs. beam mask vs. sliding window methods, respectively). For the 3D Gamma passing rates in the target, OARs, and BODY (outside target and OARs), the beam mask method improved the passing rates in these regions and the sliding window method further improved them (for prostate cancer, targets: 96.93% ± 0.53% vs. 98.88% ± 0.49% vs. 99.97% ± 0.07%, BODY: 86.88% ± 0.74% vs. 93.21% ± 0.56% vs. 95.17% ± 0.59%). A similar trend was also observed for the dice coefficients. This trend was especially remarkable for relatively low prescription isodose lines (for lung cancer, 10% isodose line dice: 0.871 ± 0.027 vs. 0.911 ± 0.023 vs. 0.927 ± 0.017). The dose predictions for all the testing cases were completed within 0.25 s.

CONCLUSIONS

An accurate and efficient deep learning-augmented proton dose prediction framework has been developed for PBSPT, which can predict accurate dose distributions not only inside but also outside ROI efficiently. The framework can potentially further reduce the initial planning and adaptive replanning workload in PBSPT.

Insurance Request and Approval Process for Proton Beam Therapy in Patients with Esophageal Cancer

PURPOSE/OBJECTIVE(S)

Randomized data suggests proton beam therapy (PBT) reduces the risk and severity of toxicities when compared to IMRT in the neoadjuvant or definitive setting for esophageal cancer. As a critical barrier to access to PBT, we investigate our institutional experience with the prior authorization (PA) process for patients (pts) with esophageal cancer.

MATERIALS/METHODS

One hundred and four (104) consecutive pts with esophageal cancer from 2016-2020 at one institution for whom PBT was recommended were analyzed. Data was collected from the customer relations management (CRM) database and electronic health record. Patient characteristics, tumor characteristics, treatment parameters, types of insurance, and clinical outcomes (OS, LF, DF) were recorded. Timepoints of the steps of the PA process included the PA team's initial inquiry, the initial decision, first through third appeals, and outcomes of each appeal (the third of which was regarded as the final decision). Rates of approval and successful appeal were calculated. Logistic and Cox regression models were used to evaluate whether insurance decisions were associated with clinical factors or clinical outcomes.

RESULTS

Approval rates by Medicare (n = 68) and private insurance (n = 36) were 100 and 42% on initial request, at a median (range) 0 and 3 (0-15) days from inquiry to determination, respectively. All 21 pts initially denied coverage appealed the decision. Overall, denial was overturned in 48% of pts (median [range] time, 14 [7-36] days from initial inquiry [FIQ]), i.e., PBT was eventually approved for them. The remaining pts proceeded with self-pay or photon therapy. Upon first appeal, 14 pts were denied (median [range] time, 7 [1-26] days FIQ). Upon second appeal, 6 pts were denied (median [range] time, 18 [7-34] days FIQ). Finally, upon third appeal, 2 pts were denied and 1 patient was approved (median [range] time, 2 [20-39] days). Medicare insurance (P < .01) and possessing secondary insurance (P = .02) were found to be associated with increased likelihood of initial approval. Notably, a trend was found between clinical trial enrollment and decreased likelihood of initial approval. Neither initial nor final insurance decisions were found to be associated with OS, LF, or DF.

CONCLUSION

Despite randomized data and policy efforts supporting the use of PBT in esophageal cancer, pts with private payers experience treatment delays and often eventual denial after appeal.

Physician and Patient-Reported Outcomes of a Phase III Trial of Ultra-Hypofractionated vs. Moderate Hypofractionated Radiotherapy to the Whole Breast after Breast-Conserving Surgery

PURPOSE/OBJECTIVE(S)

To report a final analysis evaluating physician and patient-reported outcomes of early breast cancer patients receiving moderate hypofractionation or ultra-hypofractionated whole breast radiotherapy (RT).

MATERIALS/METHODS

Between April 4, 2018, and February 11, 2020, patients with localized breast cancer (T1-T3, N0-N1, and M0) managed with breast-conserving surgery (BCS) were enrolled. Patients were randomized to receive whole breast RT with moderate hypofractionation to 40 Gy in 15 fractions (Arm A) or ultra-hypofractionation to 25 Gy in 5 fractions (Arm B). An optional concurrent integrated boost to 48 Gy on Arm A or 30 Gy on Arm B was allowed. Early toxicity (<3 months), late toxicity (> 3 months), quality of life (QOL), cosmesis, Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE), and deterioration of cosmesis were analyzed.

RESULTS

One hundred and seven patients were randomized to moderate hypofractionation (n = 54) or ultra-hypofractionation (n = 53). With a median follow-up of 36 months, no significant differences in patient characteristics were noted between the two arms. There were no patients with a grade ≥3 or higher toxicity. Grade 2 toxicities were 7.4% in Arm A and 7.5% in Arm B, and primarily consisted of radiation dermatitis (6 patients), fibrosis (1 patient) and lymphedema (1 patient). The average Harvard Cosmesis score and overall QoL were similar between arms at all time points, with no patients developing cosmetic deterioration. Patient-reported moderate to severe radiation skin burns were more commonly reported in Arm A (21.05%) vs. Arm B (6.25%) at the end of treatment (EOT) (p = 0.078). At EOT, patients receiving moderate hypofractionation had higher mean toxicity scores in breast tenderness (2.66 vs. 1.5, p = 0.018), skin flaking or peeling (0.63 vs. 0.06, p = 0.035), blistering (0.74 vs. 0.06, p = 0.028), pruritis (2.53 vs. 0.87, p < 0.001), erythema (4.24 vs. 2.0, p <0.001), telangiectasias (1.0 vs. 0.28, p = 0.021). Additionally, patients receiving moderate hypofractionation reported significantly worse changes from baseline at EOT in breast tenderness (-2.25 vs. -.86, p = 0.02), telangiectasia (-0.81 vs. 0.18, p = 0.012), skin discoloration (-4.31 vs. -1.04, p < 0.001), skin flaking or peeling (-.55 vs. 0.04, p = 0.053), blistering (-0.82 vs. -0.07, p = 0.033), and pruritus (-2.27 vs. -.67, p = 0.002). There was a return to baseline in all patient-reported breast domains by 3 months (p >0.05) in both arms.

CONCLUSION

Ultra-hypofractionated whole breast irradiation, consisting of 25 Gy in 5 fractions, provided comparable provider assessed toxicity and cosmetic outcomes to 40 Gy in 15 fractions. At the EOT assessment, ultra-hypofractionation had a better patient reported toxicity profile. Our findings provide further evidence to support daily ultra-hypofractionated whole breast radiotherapy as an appropriate treatment option for early-stage breast cancer.

Oncologic Outcomes of Conventionally Fractionated, Hypofractionated, and Stereotactic Body Spot-Scanned Proton Radiation Therapy for Prostate Cancer: The Mayo Clinic Experience

PURPOSE/OBJECTIVE(S)

Spot/pencil beam scanned proton therapy is a relatively new technology with fundamental differences from double scattered or IMRT. We aimed to report the long-term oncologic outcomes of a contemporary prospective series of patients treated with spot-scanned proton therapy (SSPT).

MATERIALS/METHODS

An IRB-approved prospective registry identified patients with prostate cancer treated with proton therapy between January 2016 and December 2018. Descriptive statistics were calculated for all patients. Clinical, demographic, and treatment characteristics were gathered and analyzed. Kaplan-Meier curves were generated to estimate survival and recurrence rates. Outcomes assessed included 5-year overall survival (OS), 5-year local control (LC), biochemical failure (BF), regional and distant failures, and physician-reported adverse events (AEs). Biochemical failure was defined as rise in PSA ≥ 2.0 ng/mL above nadir PSA. Acute and chronic gastrointestinal (GI) and genitourinary (GU) grade 2+ and grade 3+ baseline-adjusted AEs were assigned using CTCAE v5.0. All failures were re-staged with PET C-11 or PSMA.

RESULTS

With a median follow up of 4.4 years (IQR 3.7 - 5), two hundred and eighty-six prostate cancer patients with a median age of 72 (IQR 67.5 - 77) were treated with spot-scanned proton radiation. The median Gleason grade group was 3 (IQR 2 - 4). The median pre-RT PSA was 6.9 ng/mL (IQR 4.3 - 10.5). Median T-stage was T1c. Nearly 64% of all patients were on androgen deprivation therapy at the time of initiating radiation treatment. The median total radiation dose was 79.2 Gy delivered over 44 fractions, 70 Gy over 28 fractions, and 38 Gy over 5 fractions for CF, HF, and SBRT regimens, respectively. The BF rate for all patients was 8.4%. The 5-year LC rates for CF, HF, and SBRT were 100% (95% CI: 100 - 100), 100% (95% CI: 100 - 100), and 97.3% (95% CI: 92.2 - 100), respectively (p = 0.07). Regional recurrences occurred in 12 (4.2%) patients: 8 (5.6%) treated with CF, 2 (2.1%) with HF, and 2 (4.3%) with SBRT (p = 0.62). Distant metastatic failures occurred in 12 patients (4.2%): 5 (3.5%) treated with CF, 7 (7.4%) with HF, and none with SBRT (0%) (p = 0.052). The 5-year OS for patients treated with CF, HF, and SBRT SSPT were 88.2% (95% CI: 81.8 - 95), 86.2% (95% CI: 77.6 - 95.6), and 97.2% (95% CI: 92 - 100), respectively (p = 0.1). Acute and chronic grade 2+ GI baseline-adjusted AEs occurred in 8 (2.8%) and 51 (17.8%) patients, respectively. Acute and chronic grade 3+ GI baseline-adjusted AEs occurred in 3 (1%) and 4 (1.4%) patients, respectively. Acute and chronic grade 2+ GU-related AEs were observed in 72 (25.2%) and 63 (22%) patients, respectively. Acute and chronic grade 3+ GU toxicity was observed in 3 (1%) and 6 (2.1%) patients, respectively.

CONCLUSION

Spot-scanned proton radiation therapy provides high local control rates and excellent oncologic outcomes across different fractionation schedules with low long-term AE rates.

Final Analysis of a Phase III Controlled Randomized Study of Stereotactic Body Proton Therapy or Conventionally Fractionated Proton Therapy for Early Prostate Cancer: PCG GU002

PURPOSE/OBJECTIVE(S)

To determine if stereotactic body proton therapy (SBPT) is non-inferior to conventionally fractionated proton therapy (CFPT) in patients with early prostate cancer.

MATERIALS/METHODS

Multicenter, randomized, controlled, open-label, non-inferiority phase 3 trial that included patients with histologically confirmed low-risk prostate adenocarcinoma defined by Gleason score ≤6, PSA <10 ng/mL, and clinical stage T1-2a N0 M0 by AJCC 7th Ed. Eligible participants were randomly assigned (initially 1:1 and later 2:1 ratio) to CFPT (79.2 Gy in 44 fractions for 9 weeks) or SBPT (38 Gy in 5 fractions for 1 week). Concurrent or adjuvant androgen deprivation therapy was not allowed. The primary endpoint was freedom from failure (FFF) at 2 years, defined as the first occurrence of local, regional, or distant recurrence, biochemical failure by the Phoenix definition (increase of PSA ≥2 ng/mL over the nadir PSA), or the start of salvage therapy including ADT. Secondary endpoints included GI and GU grade ≥2 toxicity according to CTCAE v4 criteria, as well as health-related quality of life (HRQoL) metrics assessed by AUASI and EPIC scores. Non-inferiority would be declared if the 1-sided 95% confidence interval limit for the difference in 2-year FFF rate was below 4.2% between both groups by Clopper-Pearson exact method.

RESULTS

Between November 2010 and September 2020, 133 patients were enrolled and randomly assigned to CFPT (n = 45) or SBPT (n = 88). Median follow-up was 5 years (IQ 3.9-5.2), with the last patient enrolled followed for at least 2 years. The 2-year FFF was 100% for both groups, fulfilling the pre-specified criteria for non-inferiority of SBPT compared to CFPT. By KM estimates, 5-year FFF was 97.4% and 100% (P = 0.1), and the 5-year OS was 97.1% and 95.5% (P = 0.46) for patients treated with CFPT and SBPT, respectively. The cumulative incidence of any grade ≥3 toxicities at 5 years was 0% and 5.7% (P = 0.14) for patients treated with CFPT and SBPT, respectively. The frequency of GI grade ≥2 toxicity at 6 months was of 0% and 2.3% (P = 0.55), and at 2 years was of 6.7% and 3.4% (P = 0.69) for patients treated with CFPT and SBPT, respectively. The frequency of GU grade ≥2 toxicity at 6 months was of 2.2% and 5.7% (P = 0.42), and at 2 years was of 8.9% and 5.7% (P = 0.54) for patients treated with CFPT and SBPT, respectively. Changes in HRQoL scores at 2 years were similar between groups (Table).

CONCLUSION

SBPT is non-inferior to CFPT regarding FFF and associated with similar long-term toxicity rates and HRQoL metric scores.

Clinical Outcomes for Chest Wall Ewing Sarcoma: A Multi-Center Single Institution Experience

PURPOSE/OBJECTIVE(S)

We report tumor and treatment characteristics, oncologic outcomes, and treatment-associated toxicities in a cohort of chest wall Ewing sarcoma (cwES) patients treated at a single tertiary care institution.

MATERIALS/METHODS

After IRB approval, patients with cwES treated from 1997-2022 were retrospectively reviewed. Patient, tumor, treatment, outcomes, and toxicity data were abstracted. Local control (LC), progression-free survival (PFS), and overall survival (OS) were defined from end of treatment and assessed using the Kaplan-Meier method. Log-rank test and unadjusted Cox models were performed to determine factors associated with outcomes.

RESULTS

The cohort includes 45 patients. Median age at diagnosis was 19.8 years (range: 3.5 - 57.8 years). Five patients (11.1%) presented with pleural effusion and eight patients with lung metastases (17.8%). Two (4.4%) patients had metastatic disease outside the thorax. Median tumor volume (TV) was 138.6 mL (range: 3.0-6762.0 mL). All patients received VDC/IE chemotherapy. LC modality was surgery (S) in 21 patients (47%), radiation therapy (RT) in 5 (11%), and S+RT in 19 (42%). Median TV was larger in S+RT patients (319.4 mL, range: 5.3-6761.9 mL) compared to RT (152.3 mL, range: 20.4-366.9 mL) or S (70.4 mL, range: 3.1-1037.8 mL) (p = 0.03). R0 and R1 resections were performed in 36 (90%) and 4 (10%) patients, respectively. Proton beam therapy was used in 15 (63%) patients. Median dose was 50.40 Gy (range: 34.2 - 60 Gy) in 28 fractions to the primary tumor or post operative bed. Median dose for hemithorax (1 patient, 2.2%) and whole lung irradiation (7 patients, 15.6%) was 15.0 Gy (range: 15.0-15.0 Gy) in 10 fractions. Median follow-up was 2.38 years (range: 0 - 21.90 years). Five-year LC, PFS, and OS for all patients was 77.9% (95% CI, 65.3 - 92.9%), 54.2% (95% CI, 39.9 - 73.5%), and 63.5% (95% CI, 49.3 - 81.8%), respectively. In patients with localized disease, 5-year LC, PFS, and OS were 82.4% (95% CI, 67.9-99.8%), 66.4% (95% CI, 49.7-88.8%), and 71.3% (95% CI, 54.2-93.9%), respectively. Two-year LC by modality was 100% for RT (95% CI, 100-100%), 84.2% (95% CI, 69.3- 100%) for S and 73.3% (95% CI, 54 - 99.5%) for S+RT (p = 0.51). On univariate analysis, TV ≥ 200 mL was associated with a significantly worse 5-year OS (49.5%, TV ≥ 200 mL vs. 80.8%, TV < 200 mL; HR 4.44, p = 0.032) and PFS (35.2%, TV ≥ 200 mL vs. 76%, TV < 200 mL; HR 3.55, p = 0.025). TV ≥ 200 mL trended towards worse 5-year LC: 69.2% for TV ≥ 200 mL versus 81.5% for TV <200 mL [HR 2.26(95% CI 0.49 - 10.47), p = 0.287]. Overall, low rates of grade ≥2 toxicity were observed: 4 (8.9%) fatigue, 4 (8.9%) radiation dermatitis, 1 (2.2%) chyle leak, 3 (6.6%) scoliosis, 4 (8.9%) infection, 1 (2.2%) pneumonia, and 1 (2.2%) chest wall deformity.

CONCLUSION

RT is a safe, effective local therapy for small to moderate cwES tumors. Patients with TV ≥ 200 mL had significantly worse survival outcomes and an inferior LC rate. This suggests large cwES tumors may benefit from an aggressive multi-modality approach.

Dose delivery reproducibility for PBS proton treatment of breast cancer patients with and without mask immobilization

BACKGROUND

Setup reproducibility of the tissue in the proton beam path is critical in maintaining the planned clinical target volume (CTV) dose coverage and sparing the organs at risk (OAR). In this study, we retrospectively evaluated radiation therapy dose reproducibility for proton pencil beam scanning (PBS) treatment of breast cancer patients with and without mask immobilization.

METHODS

Ninety-four patients treated between January 2019 and September 2022 with at least one verification CT scan (V-CT) in treatment position were included for this study. All patients were set up with arms up using the Orfit AIO patient positioning system, with (69 patients) or without (25 patients) mask immobilization in chin, neck, shoulder, upper arm, and chest areas. Two to three enface or near enface single field uniform dose PBS beams were optimized using a commercial treatment planning system. Prescription doses were 25 to 60 GyRBE in 5 to 45 fractions. Treatment plan doses re-calculated on V-CTs were compared to the corresponding planned doses. Cumulative doses were also calculated for patients with at least 3 V-CTs by deform and weighted sum doses from V-CTs to corresponding P-CTs. CTV D95%, ipsilateral-lung V40%, esophagus D0.01cc, and heart mean dose were evaluated and reported as percentages of prescription doses. Differences were large dose deteriorations (LDD) if: (1) CTV (V-CT/cumulative D95%) - (Planned D95%) < - 5%; or (2) Ipsilateral-lung (V-CT/cumulative V40%) - (Planned V40%) > 5%; or (3) Esophagus (V-CT/cumulative D0.01cc) - (Planned D0.01cc) > 10%; or (4) Heart (V-CT/cumulative mean) - (Planned mean) > 1.5%.

RESULTS

On average, V-CT/cumulative and planned CTV/OAR dose parameter differences were less than 2.2%/1.7% and 3.4%/3.7% for masked and maskless patients, respectively. The percentages of patients with at least one CTV or OAR V-CT/cumulative dose LDD were 20.3%/25.0% and 72.0%/54.0% for masked and maskless patients, respectively.

CONCLUSIONS

On average, masked/maskless setups achieved delivered and planned CTV/OAR dose parameters agreed within 2.2%/3.7% for PBS treatment of breast cancer patients in this study. Maskless patients had higher rate of CTV/OAR LDDs compared to masked patients. Dosimetric differences large enough to raise clinical concerns in either group were able to be addressed with replannings.

Proton Therapy in the Adolescent and Young Adult Population

BACKGROUND

Adolescent and young adult cancer patients are at high risk of developing radiation-associated side effects after treatment. Proton beam radiation therapy might reduce the risk of these side effects for this population without compromising treatment efficacy.

METHODS

We review the current literature describing the utility of proton beam radiation therapy in the treatment of central nervous system tumors, sarcomas, breast cancer and Hodgkin lymphoma for the adolescent and young adult cancer population.

RESULTS

Proton beam radiation therapy has utility for the treatment of certain cancers in the young adult population. Preliminary data suggest reduced radiation dose to normal tissues, which might reduce radiation-associated toxicities. Research is ongoing to further establish the role of proton therapy in this population.

CONCLUSION

This report highlights the potential utility of proton beam radiation for certain adolescent young adult cancers, especially with reducing radiation doses to organs at risk and thereby potentially lowering risks of certain treatment-associated toxicities.

Beam mask and sliding window-facilitated deep learning-based accurate and efficient dose prediction for pencil beam scanning proton therapy

PURPOSE

To develop a DL-based PBSPT dose prediction workflow with high accuracy and balanced complexity to support on-line adaptive proton therapy clinical decision and subsequent replanning.

METHODS

PBSPT plans of 103 prostate cancer patients and 83 lung cancer patients previously treated at our institution were included in the study, each with CTs, structure sets, and plan doses calculated by the in-house developed Monte-Carlo dose engine. For the ablation study, we designed three experiments corresponding to the following three methods: 1) Experiment 1, the conventional region of interest (ROI) method. 2) Experiment 2, the beam mask (generated by raytracing of proton beams) method to improve proton dose prediction. 3) Experiment 3, the sliding window method for the model to focus on local details to further improve proton dose prediction. A fully connected 3D-Unet was adopted as the backbone. Dose volume histogram (DVH) indices, 3D Gamma passing rates, and dice coefficients for the structures enclosed by the iso-dose lines between the predicted and the ground truth doses were used as the evaluation metrics. The calculation time for each proton dose prediction was recorded to evaluate the method's efficiency.

RESULTS

Compared to the conventional ROI method, the beam mask method improved the agreement of DVH indices for both targets and OARs and the sliding window method further improved the agreement of the DVH indices. For the 3D Gamma passing rates in the target, OARs, and BODY (outside target and OARs), the beam mask method can improve the passing rates in these regions and the sliding window method further improved them. A similar trend was also observed for the dice coefficients. In fact, this trend was especially remarkable for relatively low prescription isodose lines. The dose predictions for all the testing cases were completed within 0.25s.

Technical note: Comprehensive evaluations of gantry and couch rotation isocentricities for implementing proton stereotactic radiosurgery

BACKGROUND

Mechanical accuracy should be verified before implementing a proton stereotactic radiosurgery (SRS) program. Linear accelerator (Linac)-based SRS systems often use electronic portal imaging devices (EPIDs) to verify beam isocentricity. Because proton therapy systems do not have EPID, beam isocentricity tests of proton SRS may still rely on films, which are not efficient.

PURPOSE

To validate that our proton SRS system meets mechanical precision requirements and to present an efficient method to evaluate the couch and gantry's rotational isocentricity for our proton SRS system.

METHODS

A dedicated applicator to hold brass aperture for proton SRS system was designed. The mechanical precision of the system was tested using a metal ball and film for 11 combinations of gantry and couch angles. A more efficient quality assurance (QA) procedure was developed, which used a scintillator device to replace the film. The couch rotational isocentricity tests were performed using orthogonal kV x-rays with the couch rotated isocentrically to 5 positions (0°, 315°, 270°, 225°, and 180°). At each couch position, the distance between the metal ball in kV images and the imaging isocenter was measured. The gantry isocentricity tests were performed using a cone-shaped scintillator and proton beams at 5 gantry angles (0°, 45°, 90°, 135°, and 180°), and the isocenter position and the distance of each beam path to the isocenter were obtained. Daily QA procedure was performed for one month to test the robustness and reproducibility of the procedure.

RESULTS

The gantry and couch rotational isocentricity exhibited sub-mm precision, with most measurements within ±0.5 mm. The one-month QA results showed that the procedure was robust and highly reproducible to within ±0.2 mm. The gantry isocentricity test using the cone-shaped scintillator was accurate and sensitive to variations of ±0.2 mm. The QA procedure was efficient enough to be completed within 30 minutes. The one-month isocentricity position variations were within 0.5 mm, which demonstrating that the overall proton SRS system was stable and precise.

CONCLUSION

The proton SRS Winston-Lutz QA procedure using a cone-shaped scintillator was efficient and robust. We were able to verify radiation delivery could be performed with sub-mm mechanical precision. This article is protected by copyright. All rights reserved.

Pragmatic, Prospective Comparative Effectiveness Trial of Carbon Ion Therapy, Surgery, and Proton Therapy for the Management of Pelvic Sarcomas (Soft Tissue/Bone) Involving the Bone: The PROSPER Study Rationale and Design

Surgical treatment of pelvic sarcoma involving the bone is the standard of care but is associated with several sequelae and reduced functional quality of life (QOL). Treatment with photon and proton radiotherapy is associated with relapse. Carbon ion radiotherapy (CIRT) may reduce both relapse rates and treatment sequelae. The PROSPER study is a tricontinental, nonrandomized, prospective, three-arm, pragmatic trial evaluating treatments of pelvic sarcoma involving the bone. Patients aged at least 15 years are eligible for inclusion. Participants must have an Eastern Cooperative Oncology Group Performance Status score of two or less, newly diagnosed disease, and histopathologic confirmation of pelvic chordoma, chondrosarcoma, osteosarcoma, Ewing sarcoma with bone involvement, rhabdomyosarcoma (RMS) with bone involvement, or non-RMS soft tissue sarcoma with bone involvement. Treatment arms include (1) CIRT (n = 30) delivered in Europe and Asia, (2) surgical treatment with or without adjuvant radiotherapy (n = 30), and (3) proton therapy (n = 30). Arms two and three will be conducted at Mayo Clinic campuses in Arizona, Florida, and Minnesota. The primary end point is to compare the 1-year change in functional QOL between CIRT and surgical treatment. Additional comparisons among the three arms will be made between treatment sequelae, local control, and other QOL measures.

Clinical Practice Evolvement for Post-Operative Prostate Cancer Radiotherapy-Part 2: Feasibility of Margin Reduction for Fractionated Radiation Treatment with Advanced Image Guidance

Purpose: Planning target volume (PTV) expansion for post-prostatectomy radiotherapy is typically ≥5 mm. Recent clinical trials have proved the feasibility of a reduced margin of 2−3 mm for treatments on MRI-linac. We aim to study the minimum PTV margin needed using iterative cone-beam CT (iCBCT) as image guidance on conventional linacs. Materials/Methods: Fourteen patients who received post-prostatectomy irradiation (8 with an endorectal balloon and 6 without a balloon) were included in this study. Treatment was delivered with volumetric modulated radiation therapy (VMAT). Fractional dose delivery was evaluated in 165 treatment fractions. The bladder, rectal wall, femoral heads, and prostate bed clinical tumor volume (CTV) were contoured and verified on daily iCBCT. PTV margins (0 mm, 2 mm, and 4 mm) were evaluated on daily iCBCT. CTV coverage and OAR dose parameters were assessed with each PTV margin. Results: CTV D100% was underdosed with a 0 mm margin in 32% of fractions in comparison with 2 mm (6%) and 4 mm (6%) PTV margin (p ≤ 0.001). CTV D95% > 95% was met in 93−94% fractions for all PTV expansions. CTV D95% > 95% was achieved in more patients with an endorectal balloon than those without: 0 mm—90/91 (99%) vs. 63/74 (85%); 2 mm—90/91 (99%) vs. 65/75 (87%); 4 mm—90/90 (100%) vs. 63/73 (86%). There was no difference in absolute median change in CTV D95% (0.32%) for 0-, 2-, and 4 mm margins. The maximum dose remained under 108% for 100% (0 mm), 97% (2 mm), and 98% (4 mm) of images. Rectal wall maximum dose remained under 108% for 100% (0 mm), 100% (2 mm), and 98% (4 mm) of images. Conclusions: With high-quality iCBCT image guidance, PTV margin accounting for inter-fractional uncertainties can be safely reduced for post-prostatectomy radiotherapy. For fractionated radiotherapy, an isotropic expansion of 2 mm and 4 mm may be considered for margin expansion with and without the endorectal balloon. Future application for margin reduction needs to be further evaluated and considered with the advent of shorter post-prostatectomy radiation courses.

Clinical Practice Evolvement for Post-Operative Prostate Cancer Radiotherapy-Part 1: Consistent Organs at Risk Management with Advanced Image Guidance

Purpose: Post-operative prostate cancer patients are treated with full bladder instruction and the use of an endorectal balloon (ERB). We reassessed the efficacy of this practice based on daily image guidance and dose delivery using high-quality iterative reconstructed cone-beam CT (iCBCT). Methods: Fractional dose delivery was calculated on daily iCBCT for 314 fractions from 14 post-operative prostate patients (8 with and 6 without ERB) treated with volumetric modulated radiotherapy (VMAT). All patients were positioned using novel iCBCT during image guidance. The bladder, rectal wall, femoral heads, and prostate bed clinical tumor volume (CTV) were contoured and verified on daily iCBCT. The dose-volume parameters of the contoured organs at risk (OAR) and CTV coverage were assessed for the clinical impact of daily bladder volume variations and the use of ERB. Minimum bladder volume was studied, and a straightforward bladder instruction was explored for easy clinical adoption. Results: A “minimum bladder” contour, the overlap between the original bladder contour and a 15 mm anterior and superior expansion from prostate bed PTV, was confirmed to be effective in identifying cases that might fail a bladder constraint of V65% <60%. The average difference between the maximum and minimum bladder volumes for each patient was 277.1 mL. The daily bladder volumes varied from 62.4 to 590.7 mL and ranged from 29 to 286% of the corresponding planning bladder volume. The bladder constraint of V65% <60% was met in almost all fractions (98%). CTVs (D90%, D95%, and D98%) remained well-covered regardless of the absolute bladder volume daily variation or the presence of the endorectal balloon. Patients with an endorectal balloon showed smaller variation but a higher average maximum rectal wall dose (D0.03mL: 104.3% of the prescription) compared to patients without (103.3%). Conclusions: A “minimum bladder” contour was determined that can be easily generated and followed to ensure sufficient bladder sparing. Further analysis and validation are needed to confirm the utility of the minimal bladder contour. Accurate dose delivery can be achieved for prostate bed target coverage and OAR sparing with or without the use of ERB.

Preliminary Analysis of a Phase II Trial of Stereotactic Body Radiation Therapy for Prostate Cancer With High-Risk Features After Radical Prostatectomy

Purpose

There are limited data regarding using stereotactic body radiation therapy (SBRT) in the postprostatectomy setting. Here, we present a preliminary analysis of a prospective phase II trial that aimed to evaluate the safety and efficacy of postprostatectomy SBRT for adjuvant or early salvage therapy.

Materials and Methods

Between May 2018 and May 2020, 41 patients fulfilled inclusion criteria and were stratified into 3 groups: group I (adjuvant), prostate-specific antigen (PSA) < 0.2 ng/mL with high-risk features including positive surgical margins, seminal vesicle invasion, or extracapsular extension; group II (salvage), with PSA ≥ 0.2 ng/mL but < 2 ng/mL; or group III (oligometastatic), with PSA ≥ 0.2 ng/mL but < 2 ng/mL and up to 3 sites of nodal or bone metastases. Androgen deprivation therapy was not offered to group I. Androgen deprivation therapy was offered for 6 months for group II and 18 months for group III patients. SBRT dose to the prostate bed was 30 to 32 Gy in 5 fractions. Baseline-adjusted physician reported toxicities (Common Terminology Criteria for Adverse Events), patient reported quality-of-life (Expanded Prostate Index Composite, Patient-Reported Outcome Measurement Information System), and American Urologic Association scores were evaluated for all patients.

Results

The median follow-up was 23 months (range, 10-37). SBRT was adjuvant in 8 (20%) patients, salvage in 28 (68%), and salvage with the presence of oligometastases in 5 (12%) patients. Urinary, bowel, and sexual quality of life domains remained high after SBRT. Patients tolerated SBRT with no grade 3 or higher (3+) gastrointestinal or genitourinary toxicities. The baseline adjusted acute and late toxicity grade 2 genitourinary (urinary incontinence) rate was 2.4% (1/41) and 12.2% (5/41). At 2 years, clinical disease control was 95%, and biochemical control was 73%. Among the 2 clinical failures, 1 was a regional node and the other a bone metastasis. Oligometastatic sites were salvaged successfully with SBRT. There were no in-target failures.

Conclusions

Postprostatectomy SBRT was very well tolerated in this prospective cohort, with no significant effect on quality of life metrics postirradiation, while providing excellent clinical disease control.

Technical note: Investigation of dose and LETd effect to rectum and bladder by using non-straight laterals in prostate cancer receiving proton therapy

BACKGROUND

Parallel-opposed lateral beams are the conventional beam arrangements in proton therapy for prostate cancer. However, when considering linear energy transfer (LET) and RBE effects, alternative beam arrangements should be investigated.

PURPOSE

To investigate the dose and dose averaged LET (LET_d ) impact of using new beam arrangements rotating beams 5°-15° posteriorly to the laterals in prostate cancer treated with pencil-beam-scanning (PBS) proton therapy.

METHODS

Twenty patients with localized prostate cancer were included in this study. Four proton treatment plans for each patient were generated utilizing 0°, 5°, 10°, and 15° posterior oblique beam pairs relative to parallel-opposed lateral beams. Dose-volume histograms (DVHs) from posterior oblique beams were analyzed. Dose-LET_d -volume histogram (DLVH) was employed to study the difference in dose and LET_d with each beam arrangement. DLVH indices, V ( d , l ) $V( {d,l} )$ , defined as the cumulative absolute volume that has a dose of at least d (Gy[RBE]) and a LET_d of at least l (keV/µm), were calculated for both the rectum and bladder to the whole group of patients and two-sub groups with and without hydrogel spacer. These metrics were tested using Wilcoxon signed-rank test.

RESULTS

Rotating beam angles from laterals to slightly posterior by 5°-15° reduced high LET_d volumes while it increased the dose volume in the rectum and increased LET_d in bladders. Beam angles rotated five degrees posteriorly from laterals (i.e., gantry in 95° and 265°) are proposed since they achieved the optimal balance of better LET_d sparing and minimal dose increase in the rectum. A reduction of V(50 Gy[RBE], 2.6 keV/µm) from 7.41 to 3.96 cc (p < 0.01), and a slight increase of V(50 Gy[RBE], 0 keV/µm) from 20.1 to 21.6 cc (p < 0.01) were observed for the group without hydrogel spacer. The LET_d sparing was less effective for the group with hydrogel spacer, which achieved the reduction of V(50 Gy[RBE], 2.6 keV/µm) from 4.28 to 2.10 cc (p < 0.01).

CONCLUSIONS

Posterior oblique angle plans improved LET_d sparing of the rectum while sacrificing LET_d sparing in the bladder in the treatment of prostate cancer with PBS. Beam angle modification from laterals to slightly posterior may be a strategy to redistribute LET_d and perhaps reduce rectal toxicity risks in prostate cancer patients treated with PBS. However, the effect is reduced for patients with hydrogel spacer.

A Phase II prospective study of hypofractionated proton therapy of prostate and pelvic lymph nodes: Acute effects on patient-reported quality of life

BACKGROUND

The objective of this study was to report acute changes in patient-reported quality of life (PRQOL) using the 26-item Expanded Prostate Index Composite (EPIC-26) questionnaire in a prospective study using hypofractionated intensity-modulated proton beam therapy (H-IMPT) targeting the prostate and the pelvic lymph nodes for high-risk or unfavorable intermediate-risk prostate cancer.

METHODS

Fifty-five patients were enrolled. H-IMPT consisted of 45 GyE to the pelvic lymph nodes and 67.5 GyE to the prostate and seminal vesicles in 25 fractions. PRQOL was assessed with the urinary incontinence (UI), urinary irritative/obstructive symptoms (UO), and bowel function (BF) domains of EPIC-26 questionnaire. Mean changes in domain scores were analyzed from pretreatment to the end of treatment and 3 months posttreatment. A clinically meaningful change (or minimum important change) was defined as a score change > 50% of the baseline standard deviation.

RESULTS

The mean scores of UO, UI, and BF at baseline were 84.6, 91.1, and 95.3, respectively. At the end of treatment, there were statistically significant and clinically meaningful declines in UO and BF scores (-13.5 and -2.3, respectively), while the decline in UI score was statistically significant but not clinically meaningful (-13.7). A clinically meaningful decline in UO, UI, and BF scores occurred in 53.5%, 22.7%, and 73.2% of the patients, respectively. At 3 months posttreatment, all three mean scores showed an improvement, with fewer patients having a clinically meaningful decline in UO, UI, and BF scores (18.4%, 20.5%, and 45.0%, respectively). There was no significant reduction in the mean UO and UI scores compared to baseline, although the mean BF score remained lower than baseline and the difference was clinically meaningful.

CONCLUSIONS

UO, UI, and BF scores of PRQOL declined at the end of H-IMPT. UO and UI scores showed improvement at 3 months posttreatment and were similar to the baseline scores. However, BF score remained lower at 3 months posttreatment with a clinically meaningful decline.

The impact of genetic aberrations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

BACKGROUND

Radium (Ra)-223 is an established treatment option for patients with metastatic castrate-resistant prostate cancer (mCRPC) who have symptomatic bone metastases without soft tissue disease. Studies have indicated genetic aberrations that regulate DNA damage response (DDR) in prostate cancer can increase susceptibility to treatments such as poly ADP-ribose polymerase inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics.

METHODS

This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota) and Tulane Cancer Center. Patient demographics, genetic aberrations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were ALP and PSA response. Secondary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment.

RESULTS

One hundred and twenty-seven mCRPC patients treated with Ra-223 had germline and/or somatic genetic sequencing. The median age at time of diagnosis and Ra-223 treatment was 61.0 and 68.6 years, respectively. Seventy-nine (62.2%) had Gleason score ≥ 8 at time of diagnosis. 50.4% received prior docetaxel, and 12.6% received prior cabazitaxel. Notable alterations include TP53 (51.7%), BRCA 1/2 (15.0%), PTEN (13.4%), ATM (11.7%), TMPRSS2-ERG (8.2%), RB deletion (3.4%), and CDK12 (1.9%). There was no significant difference in ALP or PSA response among the different genetic aberrations. Patients with a TMPRSS2-ERG mutation exhibited a trend toward lower OS 15.4 months (95% confidence interval [CI] 10.0-NR) versus 26.8 months (95% CI 20.9-35.1). Patients with an RB deletion had a lower PFS 6.0 months (95% CI 1.28-NR) versus 9.0 months (95% CI 7.3-11.1) and a lower OS 13.9 months (95% CI 5.2-NR) versus 26.5 months (95% CI 19.8-33.8).

CONCLUSIONS

Among mCRPC patients treated with Ra-223 at Mayo Clinic and Tulane Cancer Center, we did not find any clear negative predictors of biochemical response or survival to treatment. TMPRSS2-ERG and RB mutations were associated with a worse OS. Prospective studies and larger sample sizes are needed to determine the impact of genetic aberrations in response to Ra-223.

Patient-reported outcomes for patients with breast cancer undergoing radiotherapy: A single-center registry experience

Background

We present Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) for patients undergoing adjuvant radiotherapy for breast cancer with curative intent. We describe the frequency and severity of PRO-CTCAE and analyze them with respect to dose fractionation.

Methods

Patients were included in this study if they were treated with curative intent for breast cancer and enrolled on a prospective registry. Patients must have completed at least one baseline and one post-radiation survey that addressed PRO-CTCAE. For univariate and multivariate analysis, categorical variables were analyzed by Fisher’s exact test and continuous variables by Wilcoxon rank sum test. PRO-CTCAE items graded ≥2 and ≥3 were analyzed between patients who received hypofractionation (HF) versus standard conventional fractionation (CF) therapy by the Chi-square test.

Results

Three hundred thirty-one patients met inclusion criteria. Pathologic tumor stage was T1–T2 in 309 (94%) patients. Eighty-seven (29%) patients were node positive. Two hundred forty-seven patients (75%) experienced any PRO-CTCAE grade ≥2, and 92 (28%) patients experienced any PRO-CTCAE grade ≥3. CF was found to be associated with an increased risk of grade ≥3 skin toxicity, swallowing, and nausea (all p < 0.01). HF (OR 0.48, p < 0.01) was significant in the multivariate model for decreased risk of any occurrence of PRO-CTCAE ≥3.

Conclusions

Our study reports one of the first clinical experiences utilizing multiple PRO-CTCAE items for patients with breast cancer undergoing radiation therapy with curative intent. Compared with CF, HF was associated with a significant decrease in any PRO-CTCAE ≥3 after multivariate analysis.

Long-term outcomes of prostate intensity-modulated radiation therapy incorporating a simultaneous intra-prostatic MRI-directed boost

Purpose/objectives

This retrospective study demonstrates the long-term outcomes of treating prostate cancer using intensity modulated (IMRT) with incorporation of MRI-directed boost.

Materials/methods

From February 2009 to February 2013, 78 men received image-guided IMRT delivering 77.4 Gy in 44 fractions with simultaneously integrated boost to 81–83 Gy to an MRI-identified lesion. Patients with intermediate-risk or high-risk prostate cancer were recommended to receive 6 and 24–36 months of adjuvant hormonal therapy, respectively.

Results

Median follow-up was 113 months (11–147). There were 18 low-risk, 43 intermediate-risk, and 17 high-risk patients per NCCN risk stratification included in this study. Adjuvant hormonal therapy was utilized in 32 patients (41%). The 10-year biochemical control rate for all patients was 77%. The 10-year biochemical control rates for low-risk, intermediate-risk, and high-risk diseases were 94%, 81%, and 88%, respectively (p = 0.35). The 10-year rates of local control, distant control, and survival were 99%, 88%, and 66%, respectively. Of 25 patients who died, only four (5%) died of prostate cancer. On univariate analysis, T-category and pretreatment PSA level were associated with distant failure rate (p = 0.02). There was no grade =3 genitourinary and gastrointestinal toxicities that persisted at the last follow-up.

Conclusions

This study demonstrated the long-term efficacy of using MRI to define an intra-prostatic lesion for SIB to 81–83Gy while treating the entire prostate gland to 77.4 Gy with IMRT. Our study confirms that modern MRI can be used to locally intensify dose to prostate tumors providing high long-term disease control while maintaining favorable long-term toxicity.

Patient vs. Caregiver: Correlation and Differences in Pediatric Quality of Life (PedsQL) Using a Prospective Registry in a Large-Volume, Multi-Site Practice

PURPOSE

Patient reported outcomes (PROs) provide quality of life (QOL) data during and after radiation. When pediatric patients are unable to complete PROs, it is unknown whether caregiver responses are an accurate surrogate. We assessed whether caregiver scores for the Pediatric Quality of Life Inventory (PedsQL) Core and Brain Tumor Module questionnaires can substitute for missing child scores.

METHODS AND MATERIALS

From 2016-2018, pediatric patients treated with radiation were followed in a prospective, institutional registry. Child and caregiver Core and Tumor PedsQL surveys were obtained at pre-treatment, end of treatment, and in regular follow-up. The differences between the two scores at each time point were quantified using a linear mixed-model (LMM) while the level of agreement was estimated with intraclass correlation (ICC). An ICC 95% confidence interval lower limit exceeding 0.75 was considered an acceptable threshold for using caregiver scores as imputed values for missing child scores.

RESULTS

Ninety-one children completed 403 surveys. Caregivers underestimated QOL scores at baseline, but not at end of treatment or any follow-up time. The PedsQL Core total score had an ICC of 0.88 (95% CI: 0.81-0.92), while the emotional, physical, school, and social function subdomain scores were 0.81 (0.72-0.88), 0.72 (0.58-0.82), 0.79 (0.68-0.86), and 0.75 (0.62-0.83), respectively. The Tumor total score ICC was 0.91 (0.85, 0.94), and each of the subdomains (cognitive problems, communication, movement and balance, nausea, pain and hurt, perceived physical appearance, procedural anxiety, treatment anxiety, and worry) had ICC lower bound 95% CI ≥ 0.75 except for communication (0.83, 0.74-0.89). Bland-Altman analysis demonstrated no visual change in discrepancy between child and caregiver estimates as overall QOL improved.

CONCLUSION

Agreement between child and caregiver-reported QOL was generally strong in the acute period after radiation, implying that caregiver scores may be imputed for child scores in future protocols and analyses of pediatric QOL.

Toxicity and outcomes after external beam irradiation for prostate cancer in patients with prior holmium laser enucleation of the prostate: Early experience

PURPOSE/OBJECTIVES

Holmium laser enucleation of the prostate (HoLEP) is commonly performed in patients with significant bladder outlet obstruction. However, there are few reports on the toxicity of external beam irradiation (RT) for prostate cancer in patients after prior HoLEP. In this study, we evaluate the side effects and treatment outcomes of RT after HoLEP.

MATERIALS/METHODS

Eighteen patients who had HoLEP and subsequently received RT for prostate cancer were included. Data collected included patient and disease characteristics, urinary function, and radiation dose. Acute and late urinary (GU) and gastrointestinal (GI) side effects were evaluated. Disease control and survival rates were calculated using Kaplan-Meier method.

RESULTS

Median follow-up was 18 months (range: 4-46 months). Median prostate volume was 107 ml before HoLEP and 24 ml after HoLEP. Median International Prostate Symptom Score (IPSS) was 17 (range: 5-32) before HoLEP. Median decline in IPSS score after HoLEP was 7 (range: -2-21). On uroflow study, peak flow rate, and post-void residual were significantly improved after HoLEP. After radiation, peak flow rate and average flow rate showed a decline but remained significantly improved compared to pre-HoLEP measurements. Maximum acute Common Terminology Criteria for Adverse Events (CTCAE) adverse events were 12 grade 1 and 3 grade 2 for GU, and 3 grade 1 for GI, respectively. Maximum late adverse events were 13 grade 1 and 2 grade 2 for GU, and all grade 0 for GI, respectively. At last follow-up, there were 8 grade 1 and 1 grade 2 late GU, and 3 grade 1 late GI adverse events, respectively. There was no significant increase in urinary incontinence after RT compared to before RT. The 18-month biochemical control, local control, distant control rates were 78%, 94%, and 80%, respectively.

CONCLUSIONS

Patients who received RT as definitive treatment for prostate cancer after prior HoLEP had low risk of serious acute and late side effects. HoLEP can be safely performed and should be considered in patients with significant bladder outlet obstruction and large prostate volume before RT.

Implementation of Photon Treatment Back-Up Workflow at a High-Volume Proton Center: Safety, Quality, and Patient Considerations

A successful proton beam therapy (PBT) center relies heavily on the proper function and maintenance of a proton beam therapy machine. However, when a PBT machine is non-operational, a proton facility is hindered with delays that can potentially lead to inferior treatment outcome due to treatment interruption. The implementation of a workflow for which proton plans are converted to photon plans so that patients can be treated using photon has been a successful strategy to reduce delays and mitigate its impact on patient care. This workflow was established through collaboration of physicians, physicists, dosimetrists, therapists, nurses, and schedulers. A tiered system established by disease site, number of fractions, and individualized circumstances is used to prioritize patients. This article provides an overview of workflow of conversion of PBT to photon when the PBT machine is down. Specific needs of patients undergoing proton beam therapy are addressed.

A phase II trial of hypofractionated radiation therapy over five treatments for prostate cancer with high-risk features after radical prostatectomy: MC1754

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Background: Hypofractionated prostate cancer radiation has showed similar results in several prior phase III studies (PCG GU 003, PACE-B, and Hypo PC RT). However, prospective phase II-III clinical trial data testing 5 tx after prostatectomy is scarce. Methods: Between 2018 and 2019, 41 patients were treated after postprostatectomy for high risk features. 5 patients were treated adjuvantly, 36 for salvage including 8 with oligometastatic disease. Indications for adjuvant RT included a PSA < 0.2 and +margins, SVI, or EPE. Salvage RT was offered for PSA ≥0.2. Oligometastatic RT for patients with ≤5 RT targets. Staging included C11 PET for all cases. Total dose to the prostate bed was 30-32 Gy in 5tx QOD with IMRT, conebeam IGRT, and MRI registration. All salvage patients received ADT for 6 months and oligometastatic patients for 18 months. Dose to the metastatic sites was 30 in 5tx QOD. Of the 41 patients 8 also received SBRT to the sites of oligometastatic disease. We looked at clinical outcomes defining biochemical failure as a PSA > 0.2 after treatment, baseline adjusted CTC AE V5.0, baseline adjusted patient reported toxicities (PRO CTC AE), QOL (EPIC, PROMIS), and AUA was used for all cases. Results: Median follow up was 23 months (range 10-37). Pre-RT T stage was T2-T3b, with 47% being T3a-b; Pre RT Median PSA of 0.4 (range < 0.1-1.9); Median GS 8 (6-9); and (+) margins in 48.8%. Sites of oligometastatic disease radiated included the LN and bone. Treatment related AE were grade 0-1 in all cases, except for one patient with G2 GU incontinence. Overall QOL remained high during follow including Promis 10 overall, mental, and physical scores; urinary bother, irritative/obstructive, and AUA scores; bowel overall, bowel bother, and bowel function scores; and overall sexual, sexual function, and sexual bother scores remained at baseline levels during follow up. Only hormonal overall, hormonal function, and hormonal bother had lower scores at 3 months that recovered by 12 months in patients treated with ADT for 6 months and by 24 months in patients treated with ADT for 18 months. A total of 3 clinical failure have been seen; 2 patients with regional failures alone; and one with axial skeleton bony failures for 93% clinical control at median follow up of 23 months. All 3 patients with clinical failure were salvaged successfully with SBRT and all patients remain disease free at last follow up. A total 5 patients with raising PSAs alone have been seen. All patients have been re-staged with C11 PET. No failures in the prostate bed or previously radiated sites have been seen. Conclusions: Toxicity for RT over 5tx is lower than expected with only one case of grade 2 urinary incontinence. QOL scores remained high during follow up, minor changes in hormonal scores were seen during ADT, but recovered after. 30-32 Gy over 5 tx provided 100% control in radiated targets and metastatic sites. Clinical trial information: NCT03570827.

Patient-reported outcomes version of the common terminology criteria for adverse events and quality-of-life linear analogue self-assessment in breast cancer patients receiving radiation therapy: single-institution prospective registry

Purpose/objectives

We sought to investigate the impact of patient-reported outcomes version of the common terminology criteria for adverse events (PRO-CTCAE) on overall quality-of-life (QOL) employing linear analogue self-assessment (LASA) in breast cancer (BC) patients undergoing radiation therapy (RT).

Materials/methods

All patients treated with RT for BC with curative intent from 2015 to 2019 at our institution were included. Breast specific PRO-CTCAE and overall QOL LASA questionnaires were administered at baseline, end-of-treatment, 3, 6, 12 months, and then annually. Minimal clinically important difference in overall QOL was a 10-point change in LASA. Hypofractionation was any treatment > 2 Gy per fraction. Mixed models for repeated measures were used to determine the association of PRO-CTCAE and overall QOL LASA.

Results

Three hundred thirty-one (331) patients with a median follow-up of 3.1 years (range 0.4–4.9) were included. Average overall QOL LASA scores were 78.5 at baseline, 79.8 at end-of-treatment, 79.8 at 3 months, 77.1 at 6 months, 79.4 at 12 months, and 79.7 at 24 months. On univariate analysis, patients reporting a grade ≥ 3 PRO-CTCAE had, on average, a 10.4-point reduction in overall LASA QOL (p < 0.0001). On multivariate analysis, not being treated with hypofractionation and higher BMI were predictive for worse overall LASA QOL with a 10-point reduction in LASA for patients reporting a grade ≥ 3 PRO-CTCAE (p < 0.0001).

Conclusions

Patients reporting a grade ≥ 3 PRO-CTCAE experienced statistically significant and clinically meaningful deterioration in overall QOL LASA. Hypofractionation improved QOL while higher BMI predicted for worse QOL. PRO-CTCAE should be integrated into future clinical trials.

Dose-volume histogram parameters and patient-reported EPIC-Bowel domain in prostate cancer proton therapy

Purpose

To analyze rectal dose and changes in quality of life (QOL) measured with the Expanded Prostate and Cancer Index Composite (EPIC) bowel domain in patients being treated for prostate cancer with curative-intent proton beam therapy (PBT) within a large single-institution prospective registry.

Materials and Methods

Data was collected from 243 patients with localized prostate cancer treated with PBT from 2016 to 2018. The EPIC survey was administered at baseline, end-of-treatment, 3, 6, and 12 months, then annually. Dose-volume histogram (DVH) parameters for the rectum were computed, and rectal dose was analyzed using BED (α/β = 3), EQD_2Gy, and total dose. Repeated measures mixed models were implemented to determine the effect of patient, clinical, and treatment factors (including DVH) on patient-reported bowel symptom burden (EPIC-Bowel).

Results

Treatment overall resulted in changes in EPIC-Bowel scores (baseline score = 93.7), most notably at end-of-treatment (90.6) and 12 months (89.7). However, they returned to baseline at 36 months (92.9). On multivariate modeling, rectal BED D₂₅ (Gy) ≥23% was significantly associated with decline in QOL scores measuring bother (p < 0.01; 4.06 points different).

Conclusion

Rectal doses, specifically BED D₂₅ (Gy) ≥23%, are significantly associated with decline in bowel bother-related QOL in patients undergoing definitive radiotherapy for localized prostate cancer. This study demonstrates BED as an independent predictor of bowel QOL across dose fractionations of PBT.

Biologically Effective Dose and Rectal Bleeding in Definitive Proton Therapy for Prostate Cancer

Purpose and Objectives

With increasing use of hypofractionation and extreme hypofractionation for prostate cancer, rectal dose-volume histogram (DVH) parameters that apply across dose fractionations may be helpful for treatment planning in clinical practice. We present an exploratory analysis of biologically effective rectal dose (BED) and equivalent rectal dose in 2 Gy fractions (EQD2) for rectal bleeding in patients treated with proton therapy across dose fractionations.

Materials and Methods

From 2016 to 2018, 243 patients with prostate cancer were treated with definitive proton therapy. Rectal DVH parameters were obtained from treatment plans, and rectal bleeding events were recorded. The BED and EQD2 transformations were applied to each rectal DVH parameter. Univariate analysis using logistic regression was used to determine DVH parameters that were significant predictors of grade ≥ 2 rectal bleeding. Youden index was used to determine optimum cutoffs for clinically meaningful DVH constraints. Stepwise model-selection criteria were then applied to fit a “best” multivariate logistic model for predicting Common Terminology Criteria for Adverse Events grade ≥ 2 rectal bleeding.

Results

Conventional fractionation, hypofractionation, and extreme hypofractionation were prescribed to 117 (48%), 84 (34%), and 42 (17.3%) patients, respectively. With a median follow-up of 20 (2.5-40) months, 10 (4.1%) patients experienced rectal bleeding. On univariate analysis, multiple rectal DVH parameters were significantly associated with rectal bleeding across BED, EQD2, and nominal doses. The BED volume receiving 55 Gy > 13.91% was found to be statistically and clinically significant. The BED volume receiving 55 Gy remained statistically significant for an association with rectal bleeding in the multivariate model (odds ratio, 9.81; 95% confidence interval, 2.4-40.5; P = .002).

Conclusion

In patients undergoing definitive proton therapy for prostate cancer, dose to the rectum and volume of the rectum receiving the dose were significantly associated with rectal bleeding across conventional fractionation, hypofractionation, and extreme hypofractionation when using BED and EQD2 transformations.

Exploratory Investigation of Dose-Linear Energy Transfer (LET) Volume Histogram (DLVH) for Adverse Events Study in Intensity Modulated Proton Therapy (IMPT)

PURPOSE

We proposed a novel tool-a dose linear energy transfer (LET)-volume histogram (DLVH)-and performed an exploratory study to investigate rectal bleeding in prostate cancer treated with intensity modulated proton therapy.

METHODS AND MATERIALS

The DLVH was constructed with dose and LET as 2 axes, and the normalized volume of the structure was contoured in the dose-LET plane as isovolume lines. We defined the DLVH index, DLv%(d,l) (ie, v% of the structure) to have a dose of ≥d Gy and an LET of ≥l keV/μm, similar to the dose-volume histogram index Dv%. Nine patients with prostate cancer with rectal bleeding (Common Terminology Criteria for Adverse Events grade ≥2) were included as the adverse event group, and 48 patients with no complications were considered the control group. A P value map was constructed by comparison of the DLVH indices of all patients between the 2 groups using the Mann-Whitney U test. Dose-LET volume constraints (DLVCs) were derived based on the P value map with a manual selection procedure facilitated by Spearman's correlation tests. The obtained DLVCs were further cross-validated using a multivariate support vector machine (SVM)-based normal tissue complication probability (NTCP) model with an independent testing data set composed of 8 adverse event and 13 control patients.

RESULTS

We extracted 2 DLVC constraints. One DLVC was obtained, Vdose/LETboundary:2.5keVμmat 75 Gy to 3.2keVμmat8.65Gy <1.27% (DLVC1), revealing a high LET volume effect. The second DLVC, V(72.2Gy,0keVμm) < 2.23% (DVLC2), revealed a high dose volume effect. The SVM-based NTCP model with 2 DLVCs provided slightly superior performance than using dose only, with an area under the curve of 0.798 versus 0.779 for the testing data set.

CONCLUSIONS

Our results demonstrated the importance of rectal "hot spots" in both high LET (DLVC1) and high dose (DLVC2) in inducing rectal bleeding. The SVM-based NTCP model confirmed the derived DLVCs as good predictors for rectal bleeding when intensity modulated proton therapy is used to treat prostate cancer.

Unplanned implant removal in locally advanced breast cancer

Study conducted to determine frequency and timing of unplanned breast implant removal after mastectomy, reconstruction, and postmastectomy radiation (PMRT). From 2010-2017, 52 patients underwent mastectomy, reconstruction, and PMRT. With median follow-up of 3.1 years, 23 patients (44%) experienced implant removal. Implant removal occurred in 9 (17%) patients before starting PMRT and 14 (27%) patients after starting PMRT. Implant removal rates were similar for hypofractionated PMRT compared with standard fractionation and for proton compared with photon PMRT. Implant removal is common for women undergoing mastectomy and reconstruction followed by PMRT. The risk is clinically significant even before starting radiation.

Low rates of BRCA1 and BRCA2 testing for patients with ovarian cancer in ASCO's CancerLinQ, a real-world database

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Background: Ovarian cancer is the deadliest gynecological cancer and has limited screening options for early stage diagnosis. Genetic mutations in genes such as BRCA1 and BRCA2 increase the risk of ovarian cancer, and if identified, patients can undergo risk-reducing surgery. It is recommended and well accepted to test any new ovarian cancer patient for genetic mutations, particulary BRCA1 and BRCA2. If a BRCA1/2 mutation is found in a patient (somatic or germ line), this information can be used to guide therapy. We sought to analyze the characteristics of genetic testing in a real-world database, ASCO’s CancerLinQ. Methods: We performed a retrospective cohort study using the CancerLinQ Discovery database. Women with ovarian, fallopian tube, or primary peritoneal cancer were identified using ICD9 and ICD10 codes. We included patients diagnosed between 1/1/11 to 12/31/18 and age >18. We included all epithelial histologies including carcinosarcomas and excluded patients without a known histology. Results: Of the 2654 patients meeting inclusion criteria, 600 had been tested for a BRCA1/2 mutation (22.6%). Of those tested, 63% were stage III/IV, 14% stage I/II, and 21.8% an unknown stage. The majority of the histologies were serous (76%), followed by undifferentiated (21.2%). The majority of patients tested were white (69.9%), with 18.8% unknown, and 9.9% black. The rate of a positive BRCA1 or BRCA2 mutation in this population was 17.2%. Of the patients with a BRCA1/2 mutation, the majority had serous histology (87%), followed by 18.5% undifferentiated, and 3.9% transitional cell. The majority of the patients found to have a BRCA1/2 mutation were age >50 (57.3%). Conclusions: Since 2008 evidence-based guidelines have recommended that all ovarian cancer patients be tested for BRCA1 and BRCA2 mutations, but in this real-world database only 22.6% have a recorded test. Of those tested, we found a BRCA1 or BRCA2 mutation rate of 17.2%. Our data is limited by what is recorded in the database and may not represent the true number of patients tested because of data missing from the EHR; however, these percentages appear similar to previous studies. Not only is testing important for cancer prevention for family members of patients, it now impacts the type of treatments for which these patients are eligible. Since genetic testing remains low at only 22.6% in this population, significant opportunities exist to impact cancer prevention and treatment.

The impact of genetic mutations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

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Background: Radium (Ra)-223 has become the cornerstone treatment in patients with metastatic castrate-resistant prostate cancer (mCRPC) with bone metastases. Ra-223 has been shown to suppress abnormal bone formation by inducing DNA double-strand breaks in tumor cells. This can reduce skeletal-related events, as well as improve survival and quality of life. Studies have indicated mutations that regulate DNA damage response in prostate cancer as susceptible to PARP inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics. Methods: This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota). Patient demographics, genetic mutations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment. Results: 239 mCRPC patients treated with Ra-223 were identified. Germline and/or somatic genetic sequencing was available in 50 patients, who had a median age of 61 years at time of diagnosis and 68 years at time of Ra-223 treatment. Median Gleason score at time of diagnosis was 8.0. 100% of patients received prior androgen deprivation therapy. 72% received prior docetaxel, and 18% received prior cabazitaxel. Notable mutations included TP53 (45.2%), TMPRSS2-ERG (28.6%), PTEN (26.2%), BRCA1/2 (14.3%), ATM (9.3%), CDK12 (7.1%), and Rb (4.9%). TMPRSS2-ERG was the second most commonly found mutation, with median OS 12.7 mo versus 15.4 mo in patients without TMPRSS2-ERG mutations (p = 0.099). In patients with CDK12 mutations (2 of 28 tested positive), PFS was 10.4 mo versus 5.6 mo in patients without CDK12 mutations (p = 0.157). The assessment of ALP and PSA response to radium treatment stratified by genetic mutation did not reach statistical significance. Conclusions: Among mCRPC patients treated with Ra-223 at Mayo Clinic, TMPRSS2-ERG was the second most commonly found genetic mutation and had observed worse survival outcomes that approached statistical significance. Prospective studies and increased sample sizes are needed to determine the impact of genetic mutations in response to Ra-223.

Impact of Patient Stage and Disease Characteristics on the proposed Radiation Oncology Alternative Payment Model (RO-APM)

PURPOSE

The proposed Radiation Oncology Alternative Payment Model (RO-APM) released on July 10, 2019, represents a dramatic shift from fee-for-service (FFS) reimbursement in radiation therapy (RT). This study compares historical revenue at Mayo Clinic to the RO-APM and quantifies the effect that disease characteristics may have on reimbursement.

METHODS AND MATERIALS

FFS Medicare reimbursements were determined for patients undergoing RT at Mayo Clinic from 2015 to 2016. Disease categories and payment episodes were defined as per the RO-APM. Average RT episode reimbursements were reported for each disease site, except for lymphoma and metastases, and stratified by stage and disease subcategory. Comparisons with RO-APM reimbursements were made via descriptive statistics.

RESULTS

A total of 2098 patients were identified, of whom 1866 (89%) were categorized per the RO-APM; 840 (45%) of those were aged >65 years. Breast (33%), head and neck (HN) (14%), and prostate (11%) cancer were most common. RO-APM base rate reimbursements and sensitivity analysis range were lower than historical reimbursement for bladder (-40%), cervical (-34%), lung (-28%), uterine (-26%), colorectal (-24%), upper gastrointestinal (-24%), HN (-23%), pancreatic (-20%), prostate (-16%), central nervous system (-13%), and anal (-10%) and higher for liver (+24%) and breast (+36%). Historical reimbursement varied with stage (stage III vs stage I) for breast (+57%, P < .01), uterine (+53%, P = .01), lung (+50%, P < .01), HN (+24%, P = .01), and prostate (+13%, P = .01). Overall, for patients older than 65 years of age, the RO-APM resulted in a -9% reduction in total RT reimbursement compared with historical FFS (-2%, -15%, and -27% for high, mid, and low adjusted RO-APM rates).

CONCLUSIONS

Our findings indicate that the RO-APM will result in significant reductions in reimbursement at our center, particularly for cancers more common in underserved populations. Practices that care for socioeconomically disadvantaged populations may face significant reductions in revenue, which could further reduce access for this vulnerable population.

Impact of planned dose reporting methods on Gamma pass rates for IROC lung and liver motion phantoms treated with pencil beam scanning protons

PURPOSE

The purpose of this study is to evaluate the impact of two methods of reporting planned dose distributions on the Gamma analysis pass rates for comparison with measured 2D film dose and simulated delivered 3D dose for proton pencil beam scanning treatment of the Imaging and Radiation Oncology Core (IROC) proton lung and liver mobile phantoms.

METHODS AND MATERIALS

Four-dimensional (4D) computed-tomography (CT) image sets were acquired for IROC proton lung and liver mobile phantoms, which include dosimetry inserts that contains targets, thermoluminescent dosimeters and EBT2 films for plan dose verification. 4DCT measured fixed motion magnitudes were 1.3 and 1.0 cm for the lung and liver phantoms, respectively. To study the effects of motion magnitude on the Gamma analysis pass rate, three motion magnitudes for each phantom were simulated by creating virtual 4DCT image sets with motion magnitudes scaled from the scanned phantom motion by 50, 100, and 200%. The internal target volumes were contoured on the maximum intensity projection CTs of the 4DCTs for the lung phantom and on the minimum intensity projection CTs of the 4DCTs for the liver phantom. Treatment plans were optimized on the average intensity projection (AVE) CTs of the 4DCTs using the RayStation treatment planning system. Plan doses were calculated on the AVE CTs, which was defined as the planned AVE dose (method one). Plan doses were also calculated on all 10 phase CTs of the 4DCTs and were registered using target alignment to and equal-weight-summed on the 50% phase (T50) CT, which was defined as the planned 4D dose (method two). The planned AVE doses and 4D doses for phantom treatment were reported to IROC, and the 2D-2D Gamma analysis pass rates for measured film dose relative to the planned AVE and 4D doses were compared. To evaluate motion interplay effects, simulated delivered doses were calculated for each plan by sorting spots into corresponding respiratory phases using spot delivery time recorded in the log files by the beam delivery system to calculate each phase dose and accumulate dose to the T50 CTs. Ten random beam starting phases were used for each beam to obtain the range of the simulated delivered dose distributions. 3D-3D Gamma analyses were performed to compare the planned 4D/AVE doses with simulated delivered doses.

RESULTS

The planned 4D dose matched better with the measured 2D film dose and simulated delivered 3D dose than the planned AVE dose. Using planned 4D dose as institution reported planned dose to IROC improved IROC film dose 2D-2D Gamma analysis pass rate from 92 to 96% on average for three films for the lung phantom (7% 5 mm), and from 92 to 94% in the sagittal plane for the liver phantom (7% 4 mm), respectively, compared with using the planned AVE dose. The 3D-3D Gamma analysis (3% 3 mm) pass rate showed that the simulated delivered doses for lung and liver phantoms using 10 random beam starting phases for each delivered beam matched the planned 4D dose significantly better than the planned AVE dose for phantom motions larger than 1 cm (p ≤ 0.04).

CONCLUSIONS

It is recommended to use the planned 4D dose as the institution reported planned dose to IROC to compare with the measured film dose for proton mobile phantoms to improve film Gamma analysis pass rate in the IROC credentialing process.

Identifying and predicting the most costly patients in oncology

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Background: Quality based payment programs in medicine are currently being introduced nationally, aimed to improve care and reduce cost. This study aimed to evaluate the top spenders (TS) after cancer diagnosis and predict TS at two separate time points using predictive analytics. Methods: Patient characteristics, cancer details, treatments, adverse events, and outcomes were collected for patients treated for cancer at Mayo Clinic from 2007 - 2017. Standardized costs over a 2 year period after first treatment were obtained from the Mayo Clinic Cost Data Warehouse with Medicare reimbursements assigned to all services and adjusted to the 2017 GDP Implicit Price Deflator for inflation. TS were identified as those with greater than 93rd percentile costs (≥$113,158) due to a sharp rise in cost at that level. Descriptive statistics and univariate analysis were used for comparison. A prediction model with a training (80%) and validation set (20%) using multivariate selection was used to predict TS and was repeated using information available at 1) the time of consultation and 2) at last follow-up. Results: A total of 80,385 patients were included and 5,626 TS were identified. Mean cost (25th, 75th percentile) overall was $44,953 ($16,776, $51,889). Prediction models at time 1 and 2 had ROC AUC statistics of 0.82 and 0.89 in training and 0.82 and 0.88 in the validation indicating good prediction of high costs. Factors most predictive of TS included need for blood transfusions within 90 days of treatment (OR 5.3), bone marrow transplant (OR 4.0), mild liver disease (OR 3.5), hemiplegia (OR 3.4), weight loss > 10% within 90 days of treatment (OR 3.3), upper GI cancer (OR 3.0), ‘other’ cancer type (OR 2.8), immunotherapy use (OR 2.7), and hospitalizations within 90 days (OR 2.4), all p < 0.001, among others. The largest costs were due to hospital services in the TS and non-TS groups, mean costs $114,258 and $13,185 respectively. Conclusions: This is the first study to predict with high accuracy the top spenders in Oncology. Patient comorbidities and toxicities were among the strongest predictors of high costs, along with certain treatments (bone marrow transplant and immunotherapy). Our findings suggest that quality payment programs should adjust for comorbidities, and that reducing toxicity may be an effective method at reducing costs.

The cost implications of palliative radiation therapy dose and fractionation for painful metastatic bone lesions

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Background: Palliative radiation treatment (pRT) is used for symptomatic bone metastases (mets). Several fractionation schedules show equal efficacy for pain relief, and ASTRO’s Choosing Wisely recommends 8Gy x1, 4Gy x5, or 3Gy x10. This study aims to investigate the cost implications of pRT for bone mets. Methods: Patients (Pts) treated with pRT for bone mets at Mayo Clinic from 2007 - 2016 were included in this study. Costs for all services were subdivided into RT and total costs at 30 & 90 days (30D & 90D). Standardized costs were obtained from the Mayo Clinic Cost Data Warehouse and Medicare reimbursements were assigned to all services with cost to charge adjustments and 2017 GDP Implicit Price Deflator for inflation. Cost means were compared via the Kruskal-Wallis test. Results: 538 pts were treated with pRT, 124 receiving 8Gy x1, 204 receiving 4Gy x5, and 210 receiving 3Gy x10. Pts with breast and prostate cancer were most likely to be treated with 3Gy x10 and pts with GI and lung cancer were most likely to be treated with 8Gy x1. RT costs at 30D were $1,497, $1,891, and $1,982 (p=0.03) and RT costs at 90D were $2,602, $2,753, and $3,032 (p=0.08) for initial RT regimens of 8Gy x1, 4Gy x5, and 3Gy x10. Total costs of care at 30D were similar from $15,969 - 17,687 (p=0.6) and total costs at 90D were similar from $22,361 - 23,219 (p=0.7) between arms. A total of 23%, 28%, and 39% of pts were alive 2 years following pRT from each arm (p=0.07). Conclusions: This is the first study of its kind to analyze actual treatment costs for the three most common pRT regimens in bone mets. Single fraction RT was most used for pts with poor prognoses and was associated with lower RT costs at 30D, but similar RT costs at 90D, possibly due to retreatment. RT choice had no impact on overall costs of care at 30D or 90D. pRT remains of high value, representing only 11-13% of total costs.[Table: see text]

Technical Note: Using dual step wedge and 2D scintillator to achieve highly precise and robust proton range quality assurance

PURPOSE

The purpose of this study was to develop a fast method for proton range quality assurance (QA) using a dual step wedge and two-dimensional (2D) scintillator and to evaluate the robustness, sensitivity, and long-term reproducibility of this method.

METHODS

An in-house customized dual step wedge and a 2D scintillator were developed to measure proton ranges. Proton beams with homogenous fluence were delivered through wedge, and the images captured by the scintillator were used to calculate the proton ranges by a simple trigonometric method. The range measurements of 97 energies, comprising all clinically available synchrotron energies at our facility (ranges varying from 4 to 32 cm) were repeated ten times in all four gantry rooms for range baseline values. They were then used for evaluating room-to-room range consistencies. The robustness to setup uncertainty was evaluated by measuring ranges with ±2 mm setup deviations in the x, y, and z directions. The long-term reproducibility was evaluated by 1 month of daily range measurements by this method.

RESULTS

Ranges of all 97 energies were measured in less than 10 minutes including setup time. The reproducibility in a single day and daily over 1 month is within 0.1 and 0.15 mm, respectively. The method was very robust to setup uncertainty, with measured range consistencies within 0.15 mm for ±2 mm couch shifts. The method was also sensitive enough for validating range consistencies among gantry rooms and for detecting small range variations.

CONCLUSIONS

The new method of using a dual step wedge and scintillator for proton range QA was efficient, highly reproducible, and robust. This method of proton range QA was highly feasible and appealing from a workflow point of view.

Impact of Spot Size and Spacing on the Quality of Robustly Optimized Intensity Modulated Proton Therapy Plans for Lung Cancer

PURPOSE

To investigate how spot size and spacing affect plan quality, robustness, and interplay effects of robustly optimized intensity modulated proton therapy (IMPT) for lung cancer.

METHODS AND MATERIALS

Two robustly optimized IMPT plans were created for 10 lung cancer patients: first by a large-spot machine with in-air energy-dependent large spot size at isocenter (σ: 6-15 mm) and spacing (1.3 σ), and second by a small-spot machine with in-air energy-dependent small spot size (σ: 2-6 mm) and spacing (5 mm). Both plans were generated by optimizing radiation dose to internal target volume on averaged 4-dimensional computed tomography scans using an in-house-developed IMPT planning system. The dose-volume histograms band method was used to evaluate plan robustness. Dose evaluation software was developed to model time-dependent spot delivery to incorporate interplay effects with randomized starting phases for each field per fraction. Patient anatomy voxels were mapped phase-to-phase via deformable image registration, and doses were scored using in-house-developed software. Dose-volume histogram indices, including internal target volume dose coverage, homogeneity, and organs at risk (OARs) sparing, were compared using the Wilcoxon signed-rank test.

RESULTS

Compared with the large-spot machine, the small-spot machine resulted in significantly lower heart and esophagus mean doses, with comparable target dose coverage, homogeneity, and protection of other OARs. Plan robustness was comparable for targets and most OARs. With interplay effects considered, significantly lower heart and esophagus mean doses with comparable target dose coverage and homogeneity were observed using smaller spots.

CONCLUSIONS

Robust optimization with a small spot-machine significantly improves heart and esophagus sparing, with comparable plan robustness and interplay effects compared with robust optimization with a large-spot machine. A small-spot machine uses a larger number of spots to cover the same tumors compared with a large-spot machine, which gives the planning system more freedom to compensate for the higher sensitivity to uncertainties and interplay effects for lung cancer treatments.

Choosing wisely after publication of level I evidence in breast cancer radiotherapy

Background

Recent trials in early-stage breast cancer support hypofractionated whole-breast radiotherapy (WBRT) as part of breast-conserving therapy (BCT). Evidence also suggests that radiotherapy (RT) omission may be reasonable for some patients over 70 years. Among radiation-delivery techniques, intensity-modulated RT (IMRT) is more expensive than 3-dimensional conformal RT (3DCRT). Based on this evidence, in 2013, the American Society for Radiation Oncology (ASTRO) recommended hypofractionated schedules for women aged ≥50 years with early-stage breast cancer and avoiding routine use of IMRT for WBRT. To assess response to level I evidence and adherence to ASTRO recommendations, we evaluated the pattern of RT use for early-stage breast cancer at our National Comprehensive Cancer Network institution from 2006 to 2008 and 2011 to 2013 and compared the results with national trends.

Methods

Data from a prospective database were extracted to include patients treated with BCT, aged ≥50 years, with histologic findings of invasive ductal carcinoma, stage T1-T2N0M0, estrogen receptor-positive, and HER2 normal. We retrospectively reviewed the medical records and estimated costs based on 2016 Hospital Outpatient Prospective Payment System (technical fees) and Medicare Physician Fee Schedule (professional fees).

Results

Among 55 cases from 2006 to 2008, treatment regimens were 11% hypofractionated, 69% traditional schedule, and 20% RT omission (29% of patients were aged >70 years). Among 83 cases from 2011 to 2013, treatment regimens were 54% hypofractionated, 19% traditional schedule, and 27% RT omission (48% of patients were aged >70 years). 3DCRT was used for all WBRT treatments. Direct medical cost estimates were as follows: 15 fractions 3DCRT, $7,197.87; 15 fractions IMRT, $11,232.33; 25 fractions 3DCRT, $9,731.39; and 25 fractions IMRT, $16,877.45.

Conclusion

Despite apparent resistance to shorter radiation schedules in the United States, we demonstrate that rapid practice change in response to level I evidence is feasible. Wider adoption of evidence-based guidelines in early-stage breast cancer may substantially lower health care costs and improve convenience for patients without sacrificing oncologic outcomes.

Technical Note: Using experimentally determined proton spot scanning timing parameters to accurately model beam delivery time

PURPOSE

To accurately model the beam delivery time (BDT) for a synchrotron-based proton spot scanning system using experimentally determined beam parameters.

METHODS

A model to simulate the proton spot delivery sequences was constructed, and BDT was calculated by summing times for layer switch, spot switch, and spot delivery. Test plans were designed to isolate and quantify the relevant beam parameters in the operation cycle of the proton beam therapy delivery system. These parameters included the layer switch time, magnet preparation and verification time, average beam scanning speeds in x- and y-directions, proton spill rate, and maximum charge and maximum extraction time for each spill. The experimentally determined parameters, as well as the nominal values initially provided by the vendor, served as inputs to the model to predict BDTs for 602 clinical proton beam deliveries. The calculated BDTs (T_BDT ) were compared with the BDTs recorded in the treatment delivery log files (T_Log ): ∆t = T_Log -T_BDT .

RESULTS

The experimentally determined average layer switch time for all 97 energies was 1.91 s (ranging from 1.9 to 2.0 s for beam energies from 71.3 to 228.8 MeV), average magnet preparation and verification time was 1.93 ms, the average scanning speeds were 5.9 m/s in x-direction and 19.3 m/s in y-direction, the proton spill rate was 8.7 MU/s, and the maximum proton charge available for one acceleration is 2.0 ± 0.4 nC. Some of the measured parameters differed from the nominal values provided by the vendor. The calculated BDTs using experimentally determined parameters matched the recorded BDTs of 602 beam deliveries (∆t = -0.49 ± 1.44 s), which were significantly more accurate than BDTs calculated using nominal timing parameters (∆t = -7.48 ± 6.97 s).

CONCLUSIONS

An accurate model for BDT prediction was achieved by using the experimentally determined proton beam therapy delivery parameters, which may be useful in modeling the interplay effect and patient throughput. The model may provide guidance on how to effectively reduce BDT and may be used to identifying deteriorating machine performance.

Photon and Proton Radiation Therapy Utilization in a Population of More Than 100 Million Commercially Insured Patients

PURPOSE

To characterize the changes in the use of radiation therapy (RT), specifically proton beam radiation therapy (PBRT), among adult and pediatric patients over a 11-year period in a very large population of insured patients.

METHODS AND MATERIALS

We conducted a retrospective analysis of the OptumLabs Data Warehouse claims database of more than 100 million insured US enrollees. Descriptive analyses were undertaken to evaluate the characteristics of patients receiving RT from 2002 to 2012.

RESULTS

There were 474,533 patients treated with RT from 2002 to 2012. The percentage of patients treated with 3-dimensional conformal radiation therapy, 2-dimensional RT/brachytherapy, intensity modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and PBRT was 34.5%, 63.4%, 2.1%, 0.0%, and 0.1% and 40.4%, 36.0%, 21.9%, 1.1%, and 0.6% in 2002 and 2012, respectively. The greatest increase in utilization was of IMRT for prostate cancer, growing from 3.5% to 64.0%. For non-prostate cancer adults, IMRT use grew from 1.7% to 16.4%. For children, PBRT utilization increased from 0.3% to 9.7%. For prostate cancer patients, PBRT increased from 0.0% to 2.6%. For all patients, advanced technology (SBRT and PBRT) use was very low at <2%, versus 22% for IMRT.

CONCLUSIONS

This is the largest and most geographically diverse description of RT utilization. Proton beam RT utilization remains very low and has had little impact on overall RT utilization compared with IMRT. The largest shift has occurred in IMRT for prostate cancer. Our findings indicate that overall utilization of proton therapy has been low and that its use has likely had little impact on national expenditures on cancer care in the current environment.

A novel and fast method for proton range verification using a step wedge and 2D scintillator

PURPOSE

To implement and evaluate a novel and fast method for proton range verification by using a planar scintillator and step wedge.

METHODS

A homogenous proton pencil beam plan with 35 energies was designed and delivered to a 2D flat scintillator with a step wedge. The measurement was repeated 15 times (3 different days, 5 times per day). The scintillator image was smoothed, the Bragg peak and distal fall off regions were fitted by an analytical equation, and the proton range was calculated using simple trigonometry. The accuracy of this method was verified by comparing the measured ranges to those obtained using an ionization chamber and a scanning water tank, the gold standard. The reproducibility was evaluated by comparing the ranges over 15 repeated measurements. The sensitivity was evaluated by delivering to same beam to the system with a film inserted under the wedge.

RESULTS

The range accuracy of all 35 proton energies measured over 3 days was within 0.2 mm. The reproducibility in 15 repeated measurements for all 35 proton ranges was ±0.045 mm. The sensitivity to range variation is 0.1 mm for the worst case. This efficient procedure permits measurement of 35 proton ranges in less than 3 min. The automated data processing produces results immediately. The setup of this system took less than 5 min. The time saving by this new method is about two orders of magnitude when compared with the time for water tank range measurements.

CONCLUSIONS

A novel method using a scintillator with a step wedge to measure the proton range was implemented and evaluated. This novel method is fast and sensitive, and the proton range measured by this method was accurate and highly reproducible.

ACR Appropriateness Criteria for external beam radiation therapy treatment planning for clinically localized prostate cancer, part II of II

PURPOSE

To present the most updated American College of Radiology (ACR) Appropriateness Criteria formed by an expert panel on the appropriate delivery of external beam radiation to manage stage T1 and T2 prostate cancer (in the definitive setting and post-prostatectomy) and to provide clinical variants with expert recommendations based on accompanying Appropriateness Criteria for target volumes and treatment planning.

METHODS AND MATERIALS

The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a panel of multidisciplinary experts. The guideline development and revision process includes an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In instances in which evidence is lacking or equivocal, expert opinion may supplement available evidence to recommend imaging or treatment.

RESULTS

The panel summarizes the most recent and relevant literature on the topic, including organ motion and localization methods, image guidance, and delivery techniques (eg, 3-dimensional conformal intensity modulation). The panel presents 7 clinical variants, including (1) a standard case and cases with (2) a distended rectum, (3) a large-volume prostate, (4) bilateral hip implants, (5) inflammatory bowel disease, (6) prior prostatectomy, and (7) a pannus extending into the radiation field. Each case outlines the appropriate techniques for simulation, treatment planning, image guidance, dose, and fractionation. Numerical rating and commentary is given for each treatment approach in each variant.

CONCLUSIONS

External beam radiation is a key component of the curative management of T1 and T2 prostate cancer. By combining the most recent medical literature, these Appropriateness Criteria can aid clinicians in determining the appropriate treatment delivery and personalized approaches for individual patients.

Comparison of clinical outcomes with IMRT and proton therapy for prostate cancer

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Background: The ProtecT trial underscores the importance of treatment in men with prostate cancer and life expectancies > 10 years and the validity of radiation therapy (RT). RT can be given with photons or protons (PT). To address the controversy of which is better, clinical outcomes of photon-based intensity modulated RT (IMRT) and PT cohorts from 2 institutions were directly compared. Methods: Under respective IRB approvals, data from 2 cohorts were analyzed. The first was 301 men treated with ultrasound image guided IMRT from 2000-05 to 75.6 Gy in 42 fractions. The second was 1214 men treated with fiducial image guided PT from 2006-10 to 78 CGE in 39 fractions. Median age and followup were 74 y and 7.2 y for IMRT and 66 y and 5.6 y for PT. Hormone therapy (ADT) was used with IMRT and PT, respectively, in 3% and 7% of low-risk patients, 25% and 9.9% of intermediate-risk, and 91% and 57.8% of high-risk. Comparative endpoints were age-stratified 5-year (5Y) survival (OS), ≥ grade 3 gastrointestinal (GI) and urologic (GU) toxicity, and 5Y freedom from biochemical progression (FFBP). Results: There was a lower prevalence of GI (1.3% vs 0.1%, p = 0.0065) and GU (4.3% vs 0.1%, p < 0.0001) toxicity at last follow-up in the PT group. In the IMRT and PT cohorts, OS rates were 90.8% and 88.7% in men ≥75 (p = 0.4083). In men < 75, OS rates were 91.6% and 97.5% in the IMRT and PT low-risk patients (p = 0.003), 92.1% and 95.5% in the IMRT and PT intermediate-risk (p = 0.0535), and 92.0% and 90.0% (p = 0.4975) in the IMRT and PT high-risk. In the IMRT and PT cohorts, respectively, FFBP rates were 92.2% and 98.9% for low-risk patients (p < 0.0001), 87.3% and 94.5% for intermediate-risk patients(p = 0.0226), and 80.3% and 74.4% for high-risk patients (p = 0.5154). Conclusions: In this retrospective comparison of outcomes in cohorts of men treated with IMRT and PT for prostate cancer, FFBP rates were better with PT for men with low- and intermediate-risk disease and similar in men with high-risk disease despite longer and more frequent use of ADT in the IMRT cohort. This study underscores the difficulty of comparing retrospective series, with differences noted in age, RT dose, and ADT use between cohorts. However, the magnitude of improvement with PT is intriguing and warrants prospective testing.

A 20-Year Analysis of Clinical Trials Involving Proton Beam Therapy

Purpose

Clinical trials (CTs) in proton beam therapy (PBT) are important for determining its benefits relative to other treatments. An analysis of PBT trials is, thus, warranted to understand the current state of PBT CTs and the factors affecting current and future trials.

Materials and Methods

We queried the clinicaltrials.gov Website using the search terms: proton beam therapy, proton radiation, and protons. A total of 152 PBT CTs were identified. We used χ² analysis and logistic regression to evaluate trial characteristics.

Results

Most CTs were recruiting (n = 79; 52.0%), phase II (n = 95; 62.5%), open label (n = 134; 88.2%), single-group assignment (n = 84; 55.3%), and with primary treatment endpoints of safety and efficacy (n = 94; 61.8%). The primary treatment sites included gastrointestinal (n = 32; 21.1%), central nervous system (n = 31; 20.4%), lung (n = 21; 13.8%), prostate (n = 19; 12.5%), sarcoma (n = 15; 9.9%), and others (n = 24; 15.8%). Comparison studies between radiation modalities involved PBT and intensity-modulated photon therapy (n = 11; 7.2%), PBT and general photon therapy (n = 8; 5.3%), and PBT and carbon-ion therapy (n = 7; 4.6%). The PBT CTs underwent substantial growth after 2008 but now appear to be in decline. Nongovernmental institutions, comprising university centers, hospital systems, and research groups, have funded the greatest number of CTs (n= 106; 69.7%). The National Institutes of Health (NIH) were more likely to fund CTs involving the central nervous system (P = 0.02). Trials involving NIH funding were more likely to result in successful trial completion (P = 0.02).

Conclusion

Among PBT CTs, most were phase II trials, with a very few being phase III CTs. Funding of PBT CTs originating from industry or the NIH is limited. Recently, there has been a declining trajectory of newly initiated PBT trials. It is not yet clear whether this represents a true trend or just a pause in CT implementation. Despite multiple impediments to PBT CTs, the particle therapy community continues to work toward evidence generation.

Toxicity, quality of life outcomes, and dosimetric impact in phase III trial of hypofractionated or standard fractionated proton therapy for low-risk prostate cancer patients: PCG GU 002

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Background: The purpose of this study is to identify differences in toxicity, quality of life (QOL), and dosimetric endpoints among patients with low-risk prostate adenocarcinoma treated with either standard fractionation or hypofractionation proton-beam therapy. Methods: We analyzed the results of the first 75 patients treated in our phase III trial comparing 38Gy relative biological effectiveness (RBE) in 5 fractions (fx) (n = 46) vs. 79.2Gy (RBE) in 44 fx. (n = 29). All patients had low-risk prostate cancer and were treated with proton radiation using fiducial markers and daily image guidance. We evaluated American Urological Association (AUA) Symptom Index, adverse events (AEs), and Expanded Prostate Index Composite (EPIC) domains at pretreatment and 3, 6, 12, 18, 24, 36 and 48 months. Doses to the prostate were selected based on similar long term effects to normal tissue based on an α/β = 3.5 for an EQD2 of 76Gy. Results: The median follow-up was 36 months for both groups; 23 (30%) patients reached a follow-up of 48 months. We observed a small difference in AUA score (3.2 vs. 8.6, p = 0.002) at 1-year favoring the 79.2Gy arm. AUA scores were not statistically different at 18 months and after. Similarly, EPIC Urinary symptoms favored the 79.2Gy arm at 1 year (92.3 vs. 84.5, p = 0.009) and 18 months (92.3 vs. 85.3, p = 0.03); bother scores were not significantly different at any other time points. G2 or higher GU toxicity was similar between arms (p = 0.8). No differences in EPIC Bowel symptoms, EPIC Sexual symptoms, or bowel G2 or higher toxicities were seen. One death was observed in the 38Gy arm due to an unrelated case of multiple myeloma. The bladder V80 (79.2Gy arm, p = 0.04) and V39 (38Gy arm, p = 0.05) were predictive for G2 or higher GU AE. There was no association observed between rectal dose and G2 or higher rectal toxicity. Conclusions: Patients treated in the hypofractionated and standard arms tolerated treatment well. A small and temporary difference in the GU domain was seen favoring the standard arm. As predicted long term effects on the GU domain and bowel were similar for both arms, suggesting that the α/β is similar to 3.5 for long term effects. Clinical trial information: 01230866.

ACR appropriateness criteria: Permanent source brachytherapy for prostate cancer

PURPOSE

To provide updated American College of Radiology (ACR) appropriateness criteria for transrectal ultrasound-guided transperineal interstitial permanent source brachytherapy.

METHODS AND MATERIALS

The ACR appropriateness criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

RESULTS

Permanent prostate brachytherapy (PPB) is a treatment option for appropriately selected patients with localized prostate cancer with low to very high risk disease. PPB monotherapy remains an appropriate and effective curative treatment for low-risk prostate cancer patients demonstrating excellent long-term cancer control and acceptable morbidity. PPB monotherapy can be considered for select intermediate-risk patients with multiparametric MRI useful in evaluation of such patients. High-risk patients treated with PPB should receive supplemental external beam radiotherapy (EBRT) along with androgen deprivation. Similarly, patients with involved pelvic lymph nodes may also be considered for such combined treatment but reported long-term outcomes are limited. Computed tomography-based postimplant dosimetry completed within 60 days of PPB is essential for quality assurance. PPB may be considered for treatment of local recurrence after EBRT but is associated with an increased risk of toxicity.

CONCLUSIONS

Updated appropriateness criteria for patient evaluation, selection, treatment, and postimplant dosimetry are given. These criteria are intended to be advisory only with the final responsibility for patient care residing with the treating clinicians.