Conformal therapy improves the therapeutic index of patients with anal canal cancer treated with combined chemotherapy and external beam radiotherapy

Patient Outcomes With Dose Escalation Using Modern Radiotherapy Techniques: A Retrospective Review of Anal Cancer Treated at a Large Academic Institution Between 2010 and 2016

Introduction: The use of modern radiotherapy techniques (MRTs) has contributed to reduced treatment-related toxicities through better avoidance of normal structures and dose tapering, and has enabled the delivery of higher doses continuously. The purpose of this study was to review retrospectively (1) outcomes for anal cancer treated at BC Cancer (Canada) using MRT, and (2) the utilization and effect of dose escalation on cancer-related outcomes.

Methods: Patients between 2010 and 2016 with biopsy-proven anal cancer, aged >18 years, and treated with primary curative-intent chemoradiation using intensity modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) were included. Primary end points included overall survival (OS), relapse-free survival (RFS), and colostomy-free survival (CFS). Kaplan-Meier curves were created for prognostic factors, as well as dose escalation (>54 Gy vs. ≤54 Gy). Univariate and multivariate analyses were performed to evaluate predictors of the outcome.

Results: A total of 273 patients were assessed. The median age was 61 years with 70% being female, 6% HIV positive, and 68% with locally advanced cancer (T3-4, or node positive). The median follow-up time was 41.3 months. Time from diagnosis to treatment was 60 days, and treatment duration 42 days. Dose escalation was prescribed for 22, of whom 15 were locally advanced cases. A total of 97% completed their radiation, including all who were dose-escalated; 11% required unplanned treatment breaks, with over half of breaks <5 days. More than 90% completed at least half of their chemotherapy; 41% had pre-treatment, and 34% post-treatment positron emission tomography (PET) scans. For primary tumor response, 88% were complete and 10% partial; 23% relapsed, with 15% locoregional, 5% distant, and 3% both, and 12% had salvage surgery. The colostomy rate was 15%, with 4% pre-treatment, 10% relapse related, and only 1% treatment-toxicity related. On univariate analysis, male sex was associated with a higher risk of death (p=0.02) and relapse (p=0.041). Non-squamous histology was consistently a strong predictor of all outcomes (OS, p=0.0089; RFS, p<0.0001; CFS, p<0.0001) as was advanced T stage (OS, p=0.0075; RFS, p=0.0019; CFS, p=0.0099), and node positivity (OS, p=0.0014; RFS, p=0.001; CFS, p=0.0071). Age, HIV status, grade, longer treatment times (>42-day median), and lack of a pre- or post-treatment PET scan were not associated with the outcome. Dose escalation beyond 54 Gy was not significant, even among locally advanced tumors. On multivariate analysis, non-squamous histology (OS, p=0.043; RFS, p<0.001; CFS, p=0.01), T4 (OS, p=0.049; RFS, p=0.026; CFS, p=0.042) and node positivity (OS, p=0.05; RFS, p=0.006) remained significant predictors of the outcome, although node positivity was no longer significant for CFS (p=0.10).

Conclusion: BC Cancer outcomes for anal cancer treated with MRTs are comparable to what has been previously reported. Unplanned breaks were notably few, and short. Treatment-related colostomies were rare. Dose-escalated regimens were infrequently prescribed, appeared tolerable, but more often required a break. Prospective trials are needed to clarify efficacy of such regimens.

Improved treatment outcome and lower skin toxicity with intensity-modulated radiotherapy vs. 3D conventional radiotherapy in anal cancer

PURPOSE

Radiochemotherapy is the standard treatment for anal carcinoma (ACa). Intensity-modulated radiotherapy (IMRT) has been introduced, allowing focused irradiation of the tumor area. Whether physical benefits of IMRT translate to clinical benefits has not been sufficiently demonstrated.

METHODS

We retrospectively reviewed data from 82 patients with newly diagnosed ACa. Patients treated with IMRT were compared with previous patients treated with conventional three-dimensional computational radiotherapy (3D-CRT). The influence of IMRT on complete remission and acute and chronic side effects was analyzed in univariate and multivariate analyses.

RESULTS

39/40 patients treated with IMRT were in complete remission after 1 year compared to 31/39 patients treated with 3D-CRT (p = 0.014). Multivariate analysis confirmed tumor T stage as well as lack of IMRT treatment as risk factors for persistent tumor at 6 months. No significant benefits of IMRT were apparent at later timepoints (median follow up 52 months, IQR: 31.5-71.8 months). Patients treated with IMRT had a significantly lower degree of skin toxicity (median 2 vs. 3 in a scale ranging from 0 to 3, p = 0.00092). Rates of hematological toxicity/proctitis were not reduced and rates of acute diarrhea increased (p = 0.034). Median length of hospitalization tended to be shorter in patients treated with IMRT (n. s.).

CONCLUSION

We present a real-world experience of shifting radiation technique from conventional 3D-CRT to IMRT. IMRT patients had better tumor control at 1 year and lower degrees of skin toxicity. Our data indicate that IMRT can enable therapies with lower side effects with equal or better oncological results for patients with ACa.

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 (GTV_T). 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 GTV_T. Both GTV and GTV_T 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 (GTV_PET) with the GTVs based on MRI and CT (GTV_MRI). The median Dice coefficient was 0.56 when comparing the visible tumor volume evaluated by PET (GTV_{T_PET}) with the same volume evaluated by MRI (GTV_{T_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 GTV_T, which may impact future tumor boost strategies.

Long-term outcomes and toxicities of a large cohort of anal cancer patients treated with dose-painted IMRT per RTOG 0529

PURPOSE

To describe the outcomes and toxicities of the largest cohort to date of patients with anal squamous cell carcinoma uniformly treated with concurrent chemoradiation using dose-painted intensity modulated radiation therapy (DP-IMRT) according to RTOG 0529.

METHODS AND MATERIALS

We identified 99 eligible patients with anal cancer who were treated at our institution with definitive chemoradiation using DP-IMRT between 2005 and 2015 per RTOG 0529 dosing guidelines. Primary study endpoints included event-free survival (defined as recurrence, colostomy, or death) and overall survival. Secondary endpoints were treatment duration and acute and late toxicity.

RESULTS

At a median follow-up of 49 months (range, 2-114 months), 92% of patients had a clinical complete response. Fifteen percent underwent colostomy, including 4 pretreatment colostomies, 6 planned abdominoperineal resections (APRs), 4 salvage APRs, and 1 APR for treatment-related complications. Thirteen patients developed local recurrence, of whom 6 developed synchronous metastatic disease. The 4-year overall survival was 85.8%, and 4-year event-free survival was 75.5%. Median treatment duration was 43 days (range, 10-68 days). The overall rate of non-hematologic grade 3+ acute and grade 2+ late toxicities was 20% and 15%, respectively.

CONCLUSIONS

Long-term outcomes and tolerability were excellent In the largest cohort to date of patients with anal cancer who received DP-IMRT prescribed per RTOG 0529.

Dose planning objectives in anal canal cancer IMRT: the TROG ANROTAT experience

INTRODUCTION

Intensity modulated radiotherapy (IMRT) is ideal for anal canal cancer (ACC), delivering high doses to irregular tumour volumes whilst minimising dose to surrounding normal tissues. Establishing achievable dose objectives is a challenge. The purpose of this paper was to utilise data collected in the Assessment of New Radiation Oncology Treatments and Technologies (ANROTAT) project to evaluate the feasibility of ACC IMRT dose planning objectives employed in the Australian situation.

METHODS

Ten Australian centres were randomly allocated three data sets from 15 non-identifiable computed tomography data sets representing a range of disease stages and gender. Each data set was planned by two different centres, producing 30 plans. All tumour and organ at risk (OAR) contours, prescription and dose constraint details were provided. Dose-volume histograms (DVHs) for each plan were analysed to evaluate the feasibility of dose planning objectives provided.

RESULTS

All dose planning objectives for the bone marrow (BM) and femoral heads were achieved. Median planned doses exceeded one or more objectives for bowel, external genitalia and bladder. This reached statistical significance for bowel V30 (P = 0.04), V45 (P < 0.001), V50 (P < 0.001), external genitalia V20 (P < 0.001) and bladder V35 (P < 0.001), V40 (P = 0.01). Gender was found to be the only significant factor in the likelihood of achieving the bowel V50 (P = 0.03) and BM V30 constraints (P = 0.04).

CONCLUSION

The dose planning objectives used in the ANROTAT project provide a good starting point for ACC IMRT planning. To facilitate clinical implementation, it is important to prioritise OAR objectives and recognise factors that affect the achievability of these objectives.

Chemoradiotherapy for squamous cell cancer of the anal canal: a systematic review

Squamous cell cancer of the anal canal is a rare tumour for which there remains uncertainty regarding optimal therapy. A systematic review was conducted to summarise the evidence examining concurrent chemotherapy and radiotherapy or different chemotherapy regimens in combination with radiotherapy. MEDLINE, EMBASE and conference proceedings were searched for relevant randomised controlled trials. Outcomes of interest were colostomy rate, local failure, overall survival, disease-free survival, adverse effects and quality of life. Six randomised controlled trials were identified. Two trials reported lower colostomy and local failure rates for concurrent 5-fluorouracil (5-FU) plus mitomycin C (MMC) and radiotherapy compared with radiotherapy alone. The omission of MMC from this regimen resulted in higher colostomy and local failure rates and lower disease-free survival. Induction chemotherapy followed by concurrent 5-FU plus cisplatin and radiotherapy resulted in a higher colostomy rate than concurrent 5-FU plus MMC and radiotherapy. Haematological toxicity rates were lower in patients who received radiotherapy with 5-FU alone or 5-FU plus cisplatin compared with 5-FU plus MMC. No benefit was seen for the addition of induction or maintenance chemotherapy to concurrent chemoradiotherapy. The available evidence continues to support the use of radiotherapy with concurrent 5-FU and MMC as standard treatment for cancer of the anal canal to decrease colostomy and local failure rates.

Anal cancer - a review

Anal cancer accounts for only 1.5% of gastrointestinal malignancies but this disease has shown a steady increase in incidence particularly in HIV positive males. The understanding of pathophysiology and treatment of anal cancer has changed radically over last thirty years. Risk factors have been identified and organ preservation by chemoradiotherapy has become a standard. This article aims to review the clinical presentation, diagnostic evaluation, and treatment options for anal cancer in the light of current literature.

A combined accelerator mass spectrometry-positron emission tomography human microdose study with 14C- and 11C-labelled verapamil

BACKGROUND AND OBJECTIVE

In microdose studies, the pharmacokinetic profile of a drug in blood after administration of a dose up to 100 μg is measured with sensitive analytical techniques, such as accelerator mass spectrometry (AMS). As most drugs exert their effect in tissue rather than blood, methodology is needed for extending pharmacokinetic analysis to different tissue compartments. In the present study, we combined, for the first time, AMS analysis with positron emission tomography (PET) in order to determine the pharmacokinetic profile of the model drug verapamil in plasma and brain of humans. In order to assess pharmacokinetic dose linearity of verapamil, data were acquired and compared after administration of an intravenous microdose and after an intravenous microdose administered concomitantly with an oral therapeutic dose.

METHODS

Six healthy male subjects received an intravenous microdose [0.05 mg] (period 1) and an intravenous microdose administered concomitantly with an oral therapeutic dose [80 mg] of verapamil (period 2) in a randomized, crossover, two-period study design. The intravenous dose was a mixture of (R/S)-[14C]verapamil and (R)-[11C]verapamil and the oral dose was unlabelled racaemic verapamil. Brain distribution of radioactivity was measured with PET whereas plasma pharmacokinetics of (R)- and (S)-verapamil were determined with AMS. PET data were analysed by pharmacokinetic modelling to estimate the rate constants for transfer (k) of radioactivity across the blood-brain barrier.

RESULTS

Most pharmacokinetic parameters of (R)- and (S)-verapamil as well as parameters describing exchange of radioactivity between plasma and brain (influx rate constant [K(1)] = 0.030 ± 0.003 and 0.031 ± 0.005 mL/mL/min and efflux rate constant [k(2)] = 0.099 ± 0.006 and 0.095 ± 0.008 min-1 for period 1 and 2, respectively) were not statistically different between the two periods although there was a trend for nonlinear pharmacokinetics for the (R)-enantiomer. On the other hand, all pharmacokinetic parameters (except for the terminal elimination half-life [t1/2;)]) differed significantly between the (R)- and (S)-enantiomers for both periods. The maximum plasma concentration (C(max)), area under the plasma concentration-time curve (AUC) from 0 to 24 hours (AUC(24)) and AUC from time zero to infinity (AUC(∞)) were higher and the total clearance (CL), volume of distribution (V(d)) and volume of distribution at steady state (V(ss)) were lower for the (R)- than for the (S)-enantiomer.

CONCLUSION

Combining AMS and PET microdosing allows long-term pharmacokinetic data along with information on drug tissue distribution to be acquired in the same subjects thus making it a promising approach to maximize data output from a single clinical study.

Approaches using molecular imaging technology -- use of PET in clinical microdose studies

Positron emission tomography (PET) imaging uses minute amounts of radiolabeled drug tracers and thereby meets the criteria for clinical microdose studies. The advantage of PET, when compared to other analytical methods used in microdose studies, is that the pharmacokinetics (PK) of a drug can be determined in the tissue targeted for drug treatment. PET microdosing already offers interesting applications in clinical oncology and in the development of central nervous system pharmaceuticals and is extending its range of application to many other fields of pharmaceutical medicine. Although requirements for preclinical safety testing for microdose studies have been cut down by regulatory authorities, radiopharmaceuticals increasingly need to be produced under good manufacturing practice (GMP) conditions, which increases the costs of PET microdosing studies. Further challenges in PET microdosing include combining PET with other ultrasensitive analytical methods, such as accelerator mass spectrometry (AMS), to gain plasma PK data of drugs, beyond the short PET examination periods. Finally, conducting clinical PET studies with radiolabeled drugs both at micro- and therapeutic doses is encouraged to answer the question of dose linearity in clinical microdosing.

Chemo-radiation with or without mandatory split in anal carcinoma: experiences of two institutions and review of the literature

Background

The split-course schedule of chemo-radiation for anal cancer is controversial.

Methods

Eighty-four patients with invasive anal cancer treated with definitive external beam radiotherapy (RT) with a mandatory split of 12 days (52 patients, Montreal, Canada) or without an intended split (32 patients, Zurich, Switzerland) were reviewed. Total RT doses were 52 Gy (Montreal) or 59.4 Gy (Zurich) given concurrently with 5-FU/MMC.

Results

After a mean follow-up of 40 ± 27 months, overall survival and local tumor control at 5 years were 57% and 78% (Zurich) compared to 67% and 82% (Montreal), respectively. Split duration of patients with or without local relapse was 15 ± 7 d vs. 14 ± 7 d (Montreal, NS) and 11 ± 11 d vs. 5 ± 7 d (Zurich; P < 0.001). Patients from Zurich with prolonged treatment interruption (≥ 7 d) had impaired cancer-specific survival compared with patients with only minor interruption (<7 d) (P = 0.06). Bowel toxicity was associated with prolonged RT (P = 0.03) duration as well as increased relapse probability (P = 0.05). Skin toxicity correlated with institution and was found in 79% (Montreal) and 28% (Zurich) (P < 0.0001).

Conclusions

The study design did not allow demonstrating a clear difference in efficacy between the treatment regimens with or without short mandatory split. Cause-specific outcome appears to be impaired by unplanned prolonged interruption.

Anal cancer treated with radio-chemotherapy: correlation between length of treatment interruption and outcome

AIM

The purpose of this study was the evaluation of the feasibility and outcome of definitive radio-chemotherapy without split-course technique but with individualised short treatment interruption in anal cancer patients.

METHOD

Between 1993 and 2008, 101 patients with anal cancer were treated in our institution with definitive radio-chemotherapy with individualised short treatment interruptions. Treatment was halted independent of dose in case of acute grade 3 toxicities and started again until improvement. Short interruption was defined as completing treatment without exceeding six cumulative treatment days beyond a scheduled plan; otherwise, it was defined as prolonged interruption.

RESULTS

Median overall treatment time was 47 days corresponding to an interruption of six cumulative treatment days. Fifty-one patients (50%) had treatment interruption of <or=6 days. No acute grade 4 toxicities were observed. One fatality occurred during treatment due to ileus-like symptoms according to acute grade 5 toxicity. After a median follow-up of 56 months, the 5-year actuarial rates for local control comparing patients with short vs. prolonged treatment interruption were 78% vs. 81% (p = 0.904) and, for colostomy-free survival, 83% vs. 85% (p = 0.784), respectively.

CONCLUSIONS

Definitive radio-chemotherapy with short individualised treatment interruption shows high local control and colostomy-free survival rates.

Diagnosis and management of anal cancer

During the past three decades, anal cancer has served as a paradigm for the successful application of chemoradiation to solid tumors. Since the early 1990s, the increasing incidence of anal cancer in homosexual men has highlighted the causative role of oncogenic human papilloma-virus infection. This review focuses on significant trends and developments in the management of patients with squamous cell carcinoma of the anal canal, emphasizing three major aspects of diagnosis and treatment: routine screening and eradication of premalignant lesions in high-risk individuals; outcome of chemoradiation therapy in HIV-positive individuals in the era of highly active antiretroviral therapy; and potential improvements in chemoradiation protocols through improved radiation delivery technique and the combination of mitomycin with cisplatin in current prospective randomized trials.

Radiation dose associated with local control in advanced anal cancer: retrospective analysis of 129 patients

BACKGROUND AND PURPOSE

To retrospectively analyse a large consecutive cohort of patients with anal cancer for treatment-related factors influencing local control and survival.

MATERIALS AND METHODS

All patients referred for primary radiotherapy at Medical University of Vienna in 1990-2002 with anal canal carcinoma without distant metastases were analysed. Treatment consisted of external radiotherapy with or without brachytherapy and with or without chemotherapy. Patient-, tumour-, and treatment-factors were tested for influence on survival and local control using Cox multivariate analysis.

RESULTS

Median age was 67 years (n=129), the UICC stage distribution was 15%, 58%, and 27% for stages I, II, and III, respectively. With median follow-up of 8.0 years for surviving patients (3.9 years including deceased patients), five-year overall survival and disease-free-survival were 57% and 51%, respectively. Local control at 5 years was 87%. Stage and age were significant factors for overall and colostomy-free-survival, N-stage for disease-free-survival. Shorter overall treatment time favoured local control in stage T1-2 (p=.015), higher total radiation dose and female gender were associated with improved local control in T3-4 tumours (p=.021).

CONCLUSIONS

These results support potential improvement of anal cancer treatment by studying advanced technology such as IMRT, making it possible to tailor high-dose regions.

Optimal organ-sparing intensity-modulated radiation therapy (IMRT) regimen for the treatment of locally advanced anal canal carcinoma: a comparison of conventional and IMRT plans

Background

To compare the dosimetric advantage of three different intensity-modulated radiation therapy (IMRT) plans to a three dimensional (3D) conventional radiation treatment for anal cancer with regards to organs-at-risk (OAR) avoidance, including iliac bone marrow.

Methods

Five patients with T1-3 N0-1 anal cancer and five with T4 and/or N2-3 tumors were selected. Clinical tumor volume (CTV) included tumor, anal canal and inguinal, peri-rectal, and internal/external iliac nodes (plus pre-sacral nodes for T4/N2-3 tumors). Four plans were generated: (A) AP/PA with 3D conformal boost, (B) pelvic IMRT with conformal boost (C) pelvic IMRT with IMRT boost and (D) IMRT with simultaneous integrated boost (SIB). The dose for plans (A) to (C) was 45 Gy/25 followed by a 14.4 Gy/8 boost, and the total dose for plan (D) (SIB) was 59.4 Gy/33. Coverage of both PTV and the volume of OAR (small bowel, genitalia, iliac crest and femoral heads) receiving more than 10, 20, 30, and 40 Gy (V10, V20, V30, V40) were compared using non parametric statistics.

Results

Compared to plan (A), IMRT plans (B) to (D) significantly reduced the V30 and V40 of small bowel, bladder and genitalia for all patients. The V10 and V20 of iliac crests were similar for the N0-1 group but were significantly reduced with IMRT for the N2-3/T4 group (V20 for A = 50.2% compared to B = 33%, C = 32.8%, D = 34.3%). There was no statistical difference between 2-phase (arm C) and single-phase (SIB, arm D) IMRT plans.

Conclusion

IMRT is superior to 3D conformal radiation treatment for anal carcinoma with respect to OAR sparing, including bone marrow sparing.