Stability of metabolic tumor volume may enable radiotherapy dose painting in anal cancer.

PURPOSE: To evaluate the variability of the 18F-FDG-PET/CT-based metabolic tumor volume (MTV) in anal cancers during fractionated chemoradiotherapy (CRT), and assess the impact of this variability on dosimetric accuracy in MTV-targeted dose painting. METHODS: Eleven patients with anal squamous cell carcinoma who received fractionated chemoradiotherapy with curative intent were included. 18F-FDG PET/CT images were acquired at pre- and mid-treatment. Target volumes and organs at risk (OARs) were contoured manually on both image series. The MTV was generated from the PET images by thresholding. Treatment plans were retrospectively optimized for both image series using volumetric modulated arc therapy (VMAT). Standard plans prescribed 48.6 Gy, 54 Gy and 57.5 Gy in 27 fractions to elective regions, lymph node metastases and primary tumor, respectively. Dose painting plans included an extra dose level of 65 Gy to the MTV. Pre-treatment plans were transferred and re-calculated at mid-treatment basis. RESULTS: MTV decreased from pre- to mid-treatment in 10 of the 11 patients. On average, 71 % of MTVmid overlapped with MTVpre. The median and mean doses to the MTV were robust against anatomical changes, but the transferred dose painting plans had lower D98% values than the original and re-optimized plans. No major differences were found between standard and dose painting plans for OARs. CONCLUSIONS: Despite volumetric changes in the MTV, adequate dose coverage was observed in most dose painting plans. The findings indicate little or no need for adaptive dose painting at mid-treatment. Dose painting appears to be a safe treatment alternative with similar dose sparing of OARs.

Nordic anal cancer (NOAC) group consensus guidelines for risk-adapted delineation of the elective clinical target volume in anal cancer.

Background: To date, anal cancer patients are treated with radiotherapy to similar volumes despite a marked difference in risk profile based on tumor location and stage. A more individualized approach to delineation of the elective clinical target volume (CTVe) could potentially provide better oncological outcomes as well as improved quality of life. The aim of the present work was to establish Nordic Anal Cancer (NOAC) group guidelines for delineation of the CTVe in anal cancer.Methods: First, 12 radiation oncologists reviewed the literature in one of the following four areas: (1) previous delineation guidelines; (2) patterns of recurrence; (3) anatomical studies; (4) common iliac and para-aortic recurrences and delineation guidelines. Second, areas of controversy were identified and discussed with the aim of reaching consensus.Results: We present consensus-based recommendations for CTVe delineation in anal cancer regarding (a) which regions to include, and (b) how the regions should be delineated. Some of our recommendations deviate from current international guidelines. For instance, the posterolateral part of the inguinal region is excluded, decreasing the volume of irradiated normal tissue. For the external iliac region and the cranial border of the CTVe, we agreed on specifying two different recommendations, both considered acceptable. One of these recommendations is novel and risk-adapted; the external iliac region is omitted for low-risk patients, and several different cranial borders are used depending on the individual level of risk.Conclusion: We present NOAC consensus guidelines for delineation of the CTVe in anal cancer, including a risk-adapted strategy.

Deep learning-based automatic delineation of anal cancer gross tumour volume: a multimodality comparison of CT, PET and MRI.

BACKGROUND: Accurate target volume delineation is a prerequisite for high-precision radiotherapy. However, manual delineation is resource-demanding and prone to interobserver variation. An automatic delineation approach could potentially save time and increase delineation consistency. In this study, the applicability of deep learning for fully automatic delineation of the gross tumour volume (GTV) in patients with anal squamous cell carcinoma (ASCC) was evaluated for the first time. An extensive comparison of the effects single modality and multimodality combinations of computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) have on automatic delineation quality was conducted. MATERIAL AND METHODS: 18F-fluorodeoxyglucose PET/CT and contrast-enhanced CT (ceCT) images were collected for 86 patients with ASCC. A subset of 36 patients also underwent a study-specific 3T MRI examination including T2- and diffusion-weighted imaging. The resulting two datasets were analysed separately. A two-dimensional U-Net convolutional neural network (CNN) was trained to delineate the GTV in axial image slices based on single or multimodality image input. Manual GTV delineations constituted the ground truth for CNN model training and evaluation. Models were evaluated using the Dice similarity coefficient (Dice) and surface distance metrics computed from five-fold cross-validation. RESULTS: CNN-generated automatic delineations demonstrated good agreement with the ground truth, resulting in mean Dice scores of 0.65-0.76 and 0.74-0.83 for the 86 and 36-patient datasets, respectively. For both datasets, the highest mean Dice scores were obtained using a multimodal combination of PET and ceCT (0.76-0.83). However, models based on single modality ceCT performed comparably well (0.74-0.81). T2W-only models performed acceptably but were somewhat inferior to the PET/ceCT and ceCT-based models. CONCLUSION: CNNs provided high-quality automatic GTV delineations for both single and multimodality image input, indicating that deep learning may prove a versatile tool for target volume delineation in future patients with ASCC.

Treatment outcomes and prognostic factors after chemoradiotherapy for anal cancer.

BACKGROUND: Squamous cell carcinoma of the anus (SCCA) is a rare malignancy with rising incidence, associated with human papilloma virus (HPV). Chemoradiotherapy (CRT) is the preferred treatment. The purpose was to investigate treatment failure, survival and prognostic factors after CRT. MATERIAL AND METHODS: In this prospective observational study from a large regional centre, 141 patients were included from 2013 to 2017, and 132 were eligible for analysis. The main inclusion criteria were SCCA, planned radiotherapy, and performance status (ECOG) ≤2. Patient characteristics, disease stage, treatment, and treatment response were prospectively registered. Disease-free survival (DFS), overall survival (OS), and locoregional treatment failure after CRT were analysed. Hazard ratios (HRs) were estimated with Cox`s proportional hazards model. RESULTS: Median follow-up was 54 (range 6-71) months. Eighteen patients (14%) had treatment failures after CRT; of these 10 (8%) had residual tumour, and 8 (6%) relapse as first failure. The first treatment failure was locoregional (11 patients), distant (5 patients), and both (2 patients). Salvage abdomino-perineal resection was performed in 10 patients, 2 had resections of metastases, and 3 both. DFS was 85% at 3 years and 78% at 5 years. OS was 93% at 3 years and 86% at 5 years. In analyses adjusted for age and gender, HPV negative tumours (HR 2.5, p = 0.024), N3 disease (HR 2.6, p = 0.024), and tumour size ≥4 cm (HR 2.4, p = 0.038) were negative prognostic factors for DFS. CONCLUSION: State-of-the-art chemoradiotherapy for SCCA resulted in excellent outcomes, and improved survival compared with previous national data, with <15% treatment failures and a 3-year DFS of >80%.

Re-irradiation for recurrent rectal cancer - a single-center experience.

Background: There is no clear consensus on the use of re-irradiation (reRT) in the management of locally recurrent rectal cancer (LRRC). The aim of the present study was to investigate all reRT administered for rectal cancer at a large referral institution and to evaluate patient outcomes and toxicity.Material and methods: All patients with rectal cancer were identified who had received previous pelvic radiotherapy (RT) and underwent reRT during 2006-2016. Medical records and RT details of the primary tumor treatments and rectal cancer recurrence treatments were registered, including details on reRT, chemotherapy, surgery, adverse events, and long-term outcomes.Results: Of 77 patients who received ReRT, 67 had previously received pelvic RT for rectal cancer and were administered reRT for LRRC. Re-irradiation doses were 30.0-45.0 Gy, most often given as hyperfractionated RT in 1.2-1.5 Gy fractions twice daily with concomitant capecitabine. The median time since initial RT was 29 months (range, 13-174 months). Of 36 patients considered as potentially resectable, 20 underwent surgery for LRRC within 3 months after reRT. Operated patients had better 3-year overall survival (OS) (62%) compared to those who were not operated (16%; HR 0.32, p = .001). The median gross tumor volume (GTV) was 107 cm3, and 3-year OS was significantly better in patients with GTV <107 cm3 (44%) compared to patients with GTV ≥107 cm3 (21%; HR 0.52, p = .03).Conclusion: Three-year survival was significantly better for patients who underwent surgery after reRT or who had small tumor volume. Prospective clinical trials are recommended for further improvements in patient selection, outcomes, and toxicity assessment.

Anal cancer chemoradiotherapy outcome prediction using 18F-fluorodeoxyglucose positron emission tomography and clinicopathological factors.

OBJECTIVE: To assess the role of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET), obtained before and during chemoradiotherapy, in predicting locoregional failure relative to clinicopathological factors for patients with anal cancer. METHODS: 93 patients with anal squamous cell carcinoma treated with chemoradiotherapy were included in a prospective observational study (NCT01937780). FDG-PET/CT was performed for all patients before treatment, and for a subgroup (n = 39) also 2 weeks into treatment. FDG-PET was evaluated with standardized uptake values (SUVmax/peak/mean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and a proposed Z-normalized combination of MTV and SUVpeak (ZMP). The objective was to predict locoregional failure using FDG-PET, tumor and lymph node stage, gross tumor volume (GTV) and human papilloma virus (HPV) status in univariate and bivariate Cox regression analysis. RESULTS: N3 lymph node stage, HPV negative tumor, GTV, MTV, TLG and ZMP were in univariate analysis significant predictors of locoregional failure (p < 0.01), while SUVmax/peak/mean were not (p > 0.2). In bivariate analysis HPV status was the most independent predictor in combinations with N3 stage, ZMP, TLG, and MTV (p < 0.02). The FDG-PET parameters at 2 weeks into radiotherapy decreased by 30-40 % of the initial values, but neither absolute nor relative decrease improved the prediction models. CONCLUSION: Pre-treatment PET parameters are predictive of chemoradiotherapy outcome in anal cancer, although HPV negativity and N3 stage are the strongest single predictors. Predictions can be improved by combining HPV with PET parameters such as MTV, TLG or ZMP. PET 2 weeks into treatment does not provide added predictive value. ADVANCES IN KNOWLEDGE: Pre-treatment PET parameters of anal cancer showed a predictive role independent of clinicopathological factors. Although the PET parameters show substantial reduction from pre- to mid-treatment, the changes were not predictive of chemoradiotherapy outcome.

Target volume delineation of anal cancer based on magnetic resonance imaging or positron emission tomography.

PURPOSE: To compare target volume delineation of anal cancer using positron emission tomography (PET) and magnetic resonance imaging (MRI) with respect to inter-observer and inter-modality variability. METHODS: Nineteen patients with anal cancer undergoing chemoradiotherapy were prospectively included. Planning computed tomography (CT) images were co-registered with 18F-fluorodexocyglucose (FDG) PET/CT images and T2 and diffusion weighted (DW) MR images. Three oncologists delineated the Gross Tumor Volume (GTV) according to national guidelines and the visible tumor tissue (GTVT). MRI and PET based delineations were evaluated by absolute volumes and Dice similarity coefficients. RESULTS: The median volume of the GTVs was 27 and 31 cm3 for PET and MRI, respectively, while it was 6 and 11 cm3 for GTVT. Both GTV and GTVT volumes were highly correlated between delineators (r = 0.90 and r = 0.96, respectively). The median Dice similarity coefficient was 0.75 when comparing the GTVs based on PET/CT (GTVPET) with the GTVs based on MRI and CT (GTVMRI). The median Dice coefficient was 0.56 when comparing the visible tumor volume evaluated by PET (GTVT_PET) with the same volume evaluated by MRI (GTVT_MRI). Margins of 1-2 mm in the axial plane and 7-8 mm in superoinferior direction were required for coverage of the individual observer's GTVs. CONCLUSIONS: The rather good agreement between PET- and MRI-based GTVs indicates that either modality may be used for standard target delineation of anal cancer. However, larger deviations were found for GTVT, which may impact future tumor boost strategies.

Palliative pelvic radiotherapy for symptomatic rectal cancer - a prospective multicenter study.

BACKGROUND AND PURPOSE: Palliative pelvic radiotherapy (PPRT) is used to treat locally advanced rectal cancer (RC) although symptomatic effects and toxicities are poorly documented. Aims were to evaluate symptom severity, quality of life (QOL) and toxicity after PPRT. MATERIAL AND METHODS: Fifty-one patients with symptomatic primary or recurrent RC prescribed PPRT with fractions of 3 Gy to 30-39 Gy were included. Primary outcome was severity of target symptoms (TS) 12 weeks after PPRT. Pelvic symptom burden, toxicity, and QOL were assessed. Response was defined as patient-reported TS improvement or resolution. RESULTS: Pain (n = 24), rectal dysfunction (n = 16), and hematochezia (n = 9) were the most common TSs. Overall response rate among evaluable patients 12 weeks after PPRT was 28/33 (85%). Eighteen patients did not complete the study follow-up, 16 due to deteriorating health. TS responses were 10/13 (77%) for pain, 9/10 (90%) for rectal dysfunction, and 8/8 for hematochezia. Non-target pelvic symptom severity decreased and median QOL scores remained stable. There was no grade 4 toxicity. Median survival was nine months. CONCLUSIONS: In the majority of patients with symptomatic primary or recurrent RC, PPRT with 30-39 Gy contributes to pelvic symptom relief, with little toxicity. Patients prescribed PPRT of RC have limited life expectancy. Future studies should investigate simplification of PPRT.

Palliative pelvic radiotherapy for symptomatic incurable prostate cancer ­ A prospective multicenter study.

BACKGROUND AND PURPOSE: Radiotherapy is used to palliate pelvic symptoms of castration resistant prostate cancer (CRPC). However, magnitude and time course of effects and toxicities are poorly documented. Study aims were to evaluate changes in patient-reported target symptoms (TS), health-related quality of life (HRQOL) and toxicity following palliative pelvic radiotherapy (PPRT) of CRPC. MATERIAL AND METHODS: 47 patients with CRPC and a symptomatic pelvic mass prescribed PPRT with 30-39 Gy were prospectively included. Primary endpoint was patient-reported improvement or complete resolution of the TS twelve weeks after PPRT. HRQOL changes were explored. Toxicity was physician-evaluated. RESULTS: Lower urinary tract symptoms (LUTS) (45%), hematuria (26%) and pain (19%) were the most common TS. In the 40 evaluable patients, overall TS response twelve weeks after PPRT was 70%. TS responses were 8/18 for LUTS, 11/12 for hematuria, and 7/9 for pain. Global HRQOL improved transiently. The most common toxicity was grade 1 or 2 diarrhea (50%). There was no grade 4 toxicity. CONCLUSIONS: In the majority of patients with CRPC and a symptomatic pelvic tumor, PPRT with 30-39 Gy contributes to relief of hematuria, pain and other pelvic symptoms, with acceptable toxicity. Future studies should investigate whether PPRT regimens can be simplified.

Reirradiation of locally recurrent rectal cancer: a systematic review.

BACKGROUND: Many patients with rectal cancer receive radiotherapy as a component of primary multimodality treatment. Although local recurrence is infrequent, reirradiation may be needed to improve resectability and outcomes. This systematic review investigated the effects of reirradiation in terms of feasibility, toxicity, and long-term outcomes. METHODS: A Medline, Embase and Cochrane search resulted in 353 titles/abstracts. Ten publications describing seven prospective or retrospective studies were included, presenting results of 375 patients reirradiated for rectal cancer. RESULTS: Median initial radiation dose was 50.4Gy, median 8-30months before reirradiation. Reirradiation was mostly administered using hyperfractionated (1.2-1.5Gy twice-daily) or 1.8Gy once-daily chemoradiotherapy. Median total dose was 30-40Gy to the gross tumour volume with 2-4cm margins. Median survival was 39-60months in resected patients and 12-16months in palliative patients. Good symptomatic relief was reported in 82-100%. Acute toxicity with diarrhoea was reported in 9-20%, late toxicity was insufficiently reported. CONCLUSIONS: Reirradiation of rectal cancer to limited volumes is feasible. When curative resection is possible, the goal is radical resection and long-term survival, and hyperfractionated chemoradiotherapy should be preferred to limit late toxicity. Reirradiation yielded good symptomatic relief in palliative treatment.