Brachytherapy boost after chemoradiation in anal cancer: a systematic review

Purpose

Anal cancer (AC) is uncommon with approximately 4,300 new cases in both genders every year in Europe and representing only 1-2% of gastrointestinal tract tumors [1]. Squamous cell cancer (SCC) is the most frequent histological type, with about 80-85% of cases [1].
Before the 80s, the main treatment was abdominal perineal resection with anal sphincter removal leading to permanent colostomy. Five-year overall survival (OS) was between 40% and 70% with loco-regional relapse rates of approximately 35% [2,3,4]. In 1974, Nigro et al. tested low-dose external beam radiotherapy (EBRT) and concomitant chemotherapy (CT) based on 5-fluorouracil (5FU) and mitomycin C (MMC) as neoadjuvant treatment before surgery in AC treatment, reporting 2 out of 2 complete pathological responses [5]. Later, the same author reported on 28 patients with SCC of the AC treated in the same way. Surgery was done 4-6 weeks after radiation treatment and 12 patients underwent abdominal-perineal. Seven out of the 12 had no residual tumor in the surgical specimen, while one patient had microscopic tumor only; 16 patients had complete clinical response. Twenty-two patients were free of tumor and alive 1-8 years after treatment [6].
Although no randomized trials have directly compared radio-chemotherapy (RCT) and surgery, RCT nowadays represents the primary treatment of AC, while abdominal-perineal resection is reserved for patients with local failure after previous irradiation.
EBRT is the standard technique in RCT of AC [7,8]. However, the addition of brachytherapy (BRT) boost has been suggested [8]. In fact, BRT enables the delivery of higher radiation doses to small target volumes and limits the risk of radiation-induced damage to normal surrounding tissues and organs at risk. Unfortunately, the evidence supporting the use of BRT boost has never been evaluated in randomized trials or systematic reviews. Therefore, we performed this systematic review to better define the role of BRT boost in AC.

Material and methods

Bibliographic search

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and guidelines were consulted during the stages of design and data analyses [9]. We performed a systematic search of the bibliographic databases: PubMed, Scopus, and Cochrane library from the earliest possible date through January 31, 2018 [9,10,11,12]. The PubMed search strategy was: (“anus neoplasms” [MeSH Terms] OR (“anus” [All Fields] AND “neoplasms” [All Fields]) OR “anus neoplasms” [All Fields] OR (“anal” [All Fields] AND “cancer” [All Fields]) OR “anal cancer” [All Fields]) AND “brachytherapy” [MeSH Terms]).

Eligibility criteria

We included studies of any design (randomized, prospective, and retrospective), excluding case reports and trials with less than 40 patients receiving BRT boost. Studies with patients receiving also EBRT boost were considered provided ≥ 40 patients received BRT boost. Commentaries, editorials, and letters were not excluded during screening but were considered only if they reported original data. When multiple articles were found from a single study with an overlap, the study with the longest period of accrual and if necessary, data from previous publications were analyzed. Eligible intervention included BRT as a boost in AC independently of technique, dose, dose rate, and fractionation. No limits were set on CT regimens and EBRT technique. We analyzed only full text articles published in English.

Data extraction and quality assessment

Abstract and full articles from relevant studies were independently reviewed by 2 investigators (RF, SC) and those meeting the inclusion criteria were considered for further evaluation. Disagreements were resolved with involvement of all authors. In addition, we identified relevant trials from the references list of each selected article. We obtained the following information from each study: year of publication, number of centers involved, country, accrual period, patients characteristics (gender, age), tumor characteristics (histological type, tumor size, nodal status), EBRT dose and fractionation, CT schedule, BRT boost technique, delivered dose, gap between EBRT and boost, local control (LC), local-regional control (LRC), OS, colostomy-free survival (CFS), disease-free survival (DFS), toxicity scale, acute and late toxicity rate, and sphincter function.
The Scottish Intercollegiate Guidelines Network (SIGN) criteria was used to classify the quality of evidence. Briefly, SIGN level of evidence 1 is provided by meta-analyses, 2 by case control or cohort studies, 3 by non-analytic studies like case report and case series, and 4 by expert opinion [13].

Outcome assessment

At least one of the following outcomes: LC, LRC, OS, DFS, or CFS had to be present for inclusion in this review in patients receiving a BRT boost. Data about toxicity and sphincter function were included if available.

Results

Search results and quality

The literature search resulted in 428 articles. Following removal of non-pertinent papers and duplicates, 40 abstracts were selected. Following the selection criteria, 24 of the abstracts were excluded leaving 10 studies for analysis. After full-text articles assessment for eligibility, 6 more papers were excluded. Figure 1 shows the flow chart of the systematic search and review process.
Ten articles fulfilled the inclusion criteria and were considered in our review [14,15,16,17,18,19,20,21,22,23]. All studies were conducted in Europe and most reported French experiences [14,17,19,20,21,23]. No randomized controlled trials were found. All studies had retrospective design and were classified to provide a level of evidence graded as 3 according to SIGN classification [13]. Table 1 shows a summary of studies included in this systematic review. Eight studies were single center studies [14,15,16,17,18,21,22,23] and 2 were multicentric studies [19,20].

Patient and tumor characteristics

In this review, 10 studies were included (1,130 patients). Enrollment period of the studies were between 1970 and 2014. Study population and length of follow-up ranged from 47 to 221 patients and from 28.5 to 76.2 months, respectively [14,15,16,17,18,19,20,21,22,23]. Histological types other than SCC classification according to the fourth edition of the World Health Organization [24] were included in 6 studies (range, 4.5-21.3%) [15,18,19,21,22,23].

EBRT and CT characteristics

There was heterogeneity in the EBRT technique, dose, and fractionation, and in the concurrent CT schedules. In the earliest studies, EBRT was delivered by two-dimensional (2D) technique [14,15,16,17,19,20,21,22], while in the most recent series, 3D-conformal EBRT or intensity-modulated radiation therapy techniques were used [18,21]. The most frequent delivered dose was 45 Gy in 25 fractions [19,20,21,23]. The target volume was defined as anal region and pelvic nodes in all studies [13,14,15,16,17,18,19,20,21,22], while inguinal nodes were included in 8 series [15,16,18,19,20,21,22,23]. CT was used either as neoadjuvant in 3 studies [17,20,21] or concomitant treatment in all studies [14,15,16,17,18,19,20,21,22,23]. The concomitant CT schedules were heterogeneous with 1 course [14,16,17,19], 2 courses [15,16,17,18,19,20,21,23], or weekly schedules [18,21] administered in the different studies. At times, even in the same study, different CT protocols were prescribed [17,18,19,21]. MMC and 5-FU combination were the most frequently used agents [14,15,18,21,22,23]. Table 2 shows a summary of treatment features. In all studies, there was a gap between EBRT and BRT boost [14,15,16,17,18,19,20,21,22,23]. The median gap ranged from 27 to 56 days in individual studies. Before BRT boost, tumor response assessment was reported in 6 studies: in 4 studies using a digital rectal examination [17,21,22,23], in one study by ultrasound [18], while in one other study the evaluation modality was not specified [15].

BRT boost characteristics

Interstitial BRT using 192Ir source was the technique performed in all studies [14,15,16,17,18,19,20,2,22,23]. In 2 studies, an anal cylinder was inserted to displace uninvolved anal-rectal mucosa from the high-dose region [18,19]. Different dose rates were used: low-dose-rate (LDR) in 7 studies [14,15,16,17,20,21,23], pulsed-dose-rate (PDR) in three studies [19,21,22], and high-dose-rate (HDR) in one study [18]. The LDR group was the largest with 7 studies (which included 904 patients) [14,15,16,17,20,21,23]. Median prescribed dose ranged from 10 to 40 Gy. In PDR group, 3 studies (176 patients) were included [19,21,22]. Median prescribed dose ranged from 8 to 25 Gy. HDR was used only in 1 study (50 patients) based on ultrasound-guided technique (EUS). In the first 5 patients, 12 Gy in 2 fractions were prescribed but due to toxicity, dose and fractionation were changed to 8 Gy in 2 fractions in the subsequent patients [18].
The number of implanted planes was 1 in four studies [14,17,21,23], 1-2 in two series [19,22], not clearly specified in 3 analyses [15,16,20], and adapted to the target size (residual tumor after EBRT) in another study [18]. Dose prescription and planning strategies were based on the Paris system [25] in 9 studies [14,15,16,17,19,20,21,22,23]. However, in one series [22], the Paris system was used for dose specification and prescription, while dose calculation was performed using geometrical and manual optimization on Oncentra Brachytherapy Planning System (Nucletron, Veenendal, The Netherlands). On the contrary, the Paris system was not mentioned in the study of Doniec and colleagues [18], where 3D computer generated dosimetry planning was used to adequately cover the target (tumor bed), defined by the surface of visible residual tumor by trans-rectal ultrasound after EBRT.

Outcomes

The median follow-up ranged from 28.5 to 76.2 months in individual studies. LC/LRC was reported in 8 studies [15,16,18,19,20,21,22,23]. One study reported LC at 2 years (89.0%) [19]. Median 5-year LC/LRC was 78.6% (range, 70.7-92.0%) [15,16,18,20,21,22,23]. CFS was reported in 6 studies [14,19,20,21,22,23]. Median 5-year CFS was 76.1% (range, 61.4-86.4%) [14,20,21,22,23].
OS was reported in 9 studies [14,17,18,19,20,21,22,23]. One study reported the crude rate (65.9%) [14] and another study reported 90.0% 2-year OS [19]. In other studies, median 5-year OS was 69.4% (range, 63.4-82.0%), while 5-year DFS ranged from 65.9% to 85.7% (median, 75.8%) [17,18,21,22,23]. In the LDR group [14,15,16,17,20,21,23], median 5-year LC/LRC, CFS, DFS, and OS were: 78.6% (range, 70.7-89.1%), 75.2% (range, 61.4-86.4%), 78.0% (range, 65.9-85.7%), and 69.4% (63.4-73.0%), respectively. In the HDR study, 5-year LC/LRC, OS, and DFS were 92%, 74%, and 82%, respectively [18]. In the PDR group [19,21,22], one study reported the outcome at 2 years (CSF: 89%; OS: 90%) [19], while another study did not differentiate the results based on dose rate (LDR and PDR) [21]. Table 3 shows a summary of outcomes.

Toxicity

Acute toxicity was reported in 5 studies [14,17,18,21,22]. The most frequent toxicities were: cutaneous [17,21,22], hematological [17,21,22], and diarrhea [21,22]. Other reported toxicities were: intermittent anal-rectal bleeding [14], vulvo-vaginal symptoms [21], severe sphincter necrosis [18], urinary toxicity [21], nausea-vomiting [17], and painful necrotic ulcerations [14]. Late toxicity was reported in 8 studies [14,15,17,18,19,21,22,23]. The most frequent were radio-necrosis [14,15,17,19], rectal bleeding [14,17,19,22], proctitis [15,22,23], and incontinence [15,18,19,23]. Some studies reported anal ulceration [17], cystitis [23], and pain [19,23]. Table 4 shows a summary of acute and late toxicity results in more detail.
Permanent colostomy related to toxicity was reported in 8 studies [14,15,17,18,19,20,21,23], with 3.7% median rate (range, 2.7-5.3%) [14,15,17,18,19,20,21,23]. The most frequent toxicities leading to colostomy were: radio-necrosis [14,15,17,18,19], incontinence [15,18,23], and bleeding [14].
The sphincter function was evaluated in 2 studies [15,21]. Lestrade and coworkers used Womack’s scale [26] and the results were: total continence to gas in 82.0% of patients, incontinence to gas in 15.0%, and incontinence to liquid stools in 3.0% of patients [21]. In the study of Sandhu et al., where the used scale was not reported, 71.0% of patients were totally continent with normal anal function [15].

Comparisons

No direct comparison between different dose rates was found in this systematic review, while 4 studies reported patients who also underwent EBRT boost [16,17, 20,22] and some comparisons were performed.
In the CORS-03 study, overall treatment time (OTT) was longer in EBRT boost (median, 82 days) compared to BRT group (median, 69 days). BRT boost technique in both univariate and multivariate analysis was associated with lower local recurrence rates (LRR). In the group of patients with OTT < 80 days, 5-year local relapse rate was significantly reduced by BRT boost (BRT: 9.0% vs. EBRT: 28.0%; p = 0.03). On the contrary, in the OTT ≥ 80 days group, LRR was not significantly affected by the boost technique (BRT: 29.0% vs. EBRT: 38.0%; p = 0.21). Other statistically significant factors associated with lower LRR were T1-2 stage and OTT (OTT < 80 days: 14.0%, OTT ≥ 80 days: 34.0%; p = 0.005). In the multivariate analysis, OTT and nodal status were the only prognostic factors for CFS and OS. No correlation was observed between boost technique and OS and CFS [23].
Gryc and colleagues reported no differences in locoregional recurrences (24.0% vs. 19.0%), CFS (76.1% vs. 82.1%), OS (64% vs. 69%), and grade 4 late proctitis (2.0% vs. 1.0%) between BRT boost and EBRT boost, despite higher rate of patients with residual disease at 6 weeks after RCT in the BRT group [22]. Chapet et al. in univariate analysis observed an improvement of OS in patients treated with BRT boost, but it was not confirmed at multivariate analysis. Age (≤ 75 years) and tumor response after the first radiotherapy course significantly correlated with OS at multivariate analysis (p = 0.01). Patients treated with LDR BRT boost technique, concurrent CT, and with better tumor response before boost showed higher DFS at multivariate analysis [17]. In the series of Lestrade and colleagues, the risk of severe late toxicity was increased in patients receiving a total dose higher than the median value, with 2.7% and 10.0% rates after doses of ≤ 63 Gy versus > 63 Gy (p = 0.02), respectively. At multivariate analysis, concomitant CT (p = 0.008) and LC (p < 0.001) had a positive impact on OS [21].

Discussion

RCT is currently the standard treatment of AC with 5-year LC ranging between 68% and 87% [27,28,29,30], while surgery is reserved only for patients with local failure after previous irradiation. We performed this analysis to define the role, optimal dose, and techniques of BRT boost in AC. Ten studies were included in this systematic review [14,15,16,17,18,19,20,21,22,23].
From this review, median 5-year LC/LRC, CFS, and OS were: 78.6% (range, 70.7-92.0%), 76.1% (range, 61.4-86.4%), and 75.8% (range, 65.9-85.7%), respectively.
In the studies with delivered doses lower than 40 Gy, no data about LC/LRC were reported [14,17]. From LDR studies with total EBRT dose > 40 Gy [15,20,21,23], Sandhu et al. used the highest BRT boost dose (range, 20-40 Gy) and reported LC crude value of 78.0% [15]. Doniec et al. used HDR irradiation modality with a dose of 8-12 Gy given in 2 fractions using endorectal ultrasound (US)-guided technique and reported a LC rate of 92.0% [18]. This positive result might have been related to the optimal identification of the residual disease in real time during the implant. Unfortunately, this cannot be confirmed by other studies due to the different dose-rates used.
The lowest CFS was reported in the earliest study (61.4% crude value) and this result could be related to low EBRT total dose (35 Gy/15 fractions) [14]. The lowest DFS (65.9%) [14] and the lowest OS (63.4%) [17] were recorded in the two earliest series in terms of enrollment. According to the European Society for Medical Oncology- European Society of Surgical Oncology-European Society of Radiotherapy and Oncology AC guidelines 2014, the standard dose recommended for T1-T2 is at least 45-50 Gy, and even higher doses are recommended for more advanced tumors [8].
Due to heterogeneity of the scoring systems, in some studies not explicitly reported [14,15,16,18,20,22], comparisons about toxicity are particularly difficult. Most frequently reported severe acute toxicities were: skin (range, 2.0-5.7%) [21,22], bone marrow (range, 0.4-26.0%) [17,21,22], and bowel (range, 1.4-6.0%) [21,22]. The lowest rate of toxicity was reported by Doniec et al., who used 3D-EBRT followed by 3D-US-guided HDR-BRT boost with an anal cylinder in place to supersede uninvolved mucosa from the high dose area [18]. Due to the lack of comparison with other studies, it is difficult to define the relative contribution of all these factors. Severe late toxicity requiring permanent colostomy ranged from 2.7% to 5.3% [14,15,17,18,19,20,21,23], in most cases due to incontinence (range, 3.8-4.0%) [15,18,23], and bleeding (2.7%) [14]. Clear correlations between BRT technique and toxicity-induced colostomy rates are lacking.
In this review, only two studies reported the sphincter function and again it is difficult to make any meaningful comparisons [15,21]. Furthermore, none of the analyzed studies included in this review reported quality of life (QoL) of patients undergoing BRT boost with a formal assessment. However, lack of an anal cancer-specific QoL measure is not only limited to patients treated with BRT boost, even to RCT alone [30].
To evaluate more specifically the role of a BRT boost, we compared the results of patients treated with RCT ± boost in randomized trials [27,28,29,31,32] with the ones of the current review. Of course, we report this data being aware of the difficulty and the high-risk of bias in comparing randomized trials with retrospective series. In the randomized trials, 5-year LC/LRC, CFS, and OS with RCT alone were: 74.0% (range, 67.7-83%), 71.5% (range, 46.9-77.1%), and 68.2% (range, 56-80%), respectively. Therefore, the current systematic analysis showed higher outcomes regarding every endpoint hence supporting the addition of BRT boost after RCT in AC. In our analysis, we chose a relatively high threshold of 40 patients in order to analyze only numerically representative series and therefore, with more reliable results due to higher statistical homogeneity. However, some interesting series [33,34,35] with smaller sample size (< 40 patients receiving BRT boost) have been published in the last decades. Saarilahti et al. reported a trend towards lower incidence of radiation proctitis in patients receiving the final boost dose by HDR-BRT compared to EBRT (p = 0.065) [33]. In the series of Widder et al. the delivery of BRT boost was not significantly related to survival, LC, or time to colostomy at multivariate regression analysis [34]. Falk et al. treated 28 patients by split-course EBRT and HDR-BRT with or without CT. Two-year LRC, DFS, and OS were 83%, 71.8%, and 87.7%, respectively [35].
In terms of comparison between the different studies using BRT boost, it should be stressed that the best results in terms of LC and acute toxicity were recorded in the study using 3D-US-guided BRT. This suggests that the use of advanced techniques could improve the results of BRT boost. Further improvements could be produced by more sophisticated planning and delivery techniques. Tagliaferri et al. [36] described their advanced BRT technique experience in AC. They evaluated the feasibility of using multiparametric MRI with compatible applicator for image-guided adaptive brachytherapy (IABT). With 11 patients included in the study, the median target volume covered by 200%, 150%, 100%, 90%, and 85% of the prescription dose were 24.6%, 53.4%, 93.5%, 97.6%, and 98.7%, respectively. The median coverage index and median overdose volume index were 0.94 and 0.27, respectively. The authors concluded that multiparametric MR/CT-IABT for AC is feasible and promising based on the planning results [36].
This review is the first to systematically summarize the results of BRT as boost in AC. The level of evidence of the studies was low, 3 according to SIGN criteria. We used this relatively simple system being aware of the lack of prospective studies in literature. Therefore, a proper assessment of this treatment modality should require prospective trials possibly based on advanced delivery techniques as image-guided adaptive BRT.

Disclosure

The authors report no conflict of interest.

References

1. Jemal A, Simard EP, Dorell C et al. Annual report to the nation on the status of cancer, 1975-2009, featuring the burden and trends in human papillomavirus (HPV)-associated cancers and HPV vaccination coverage levels. J Natl Cancer Inst 2013; 105: 175-201.
2. Boman BM, Moertel CG, O’Connell MJ et al. Carcinoma of the anal canal. A clinical and pathologic study of 188 cases. Cancer 1984; 54: 114-125.
3. Greenall MJ, Quan SH, Urmacher C et al. Treatment of epidermoid carcinoma of the anal canal. Surg Gynecol Obstet 1985; 161: 509-517.
4. Dougherty BG, Evans HL. Carcinoma of the anal canal: A study of 79 cases. Am J Clin Pathol 1985; 83: 159-164.
5. Nigro ND, Vaitkevicius VK, Considine B Jr. Combined therapy for cancer of the anal canal: A preliminary report. Dis Colon Rectum 1974; 17: 354-356.
6. Nigro ND, Seydel HG, Considine B et al. Combined preoperative radiation and chemotherapy for squamous cell carcinoma of the anal canal. Cancer 1983; 51: 1826-1829.
7. http://www.nccn.org/professionals/physician_gls/f_guidelines.asp#anal. Accessed: 31 January 2018.
8. Glynne-Jones R, Nilsson PJ, Aschele C et al. Anal cancer: ESMO-ESSO-ESTRO clinical practice guidelines for diagnosis, treatment and follow-up. Eur J Surg Oncol 2014; 40: 1165-1176.
9. Hutton B, Salanti G, Caldwell DM et al. The PRISMA Extension Statement for Reporting of Systematic Reviews Incorporating Network Meta-analyses of Health Care Interventions: Checklist and Explanations. Ann Intern Med 2015; 162: 777-784.
10. http://www.ncbi.nlm.nih.gov/pubmed. Accessed: 31 January 2018.
11. http://www.scopus.com/. Accessed: 31 January 31 2018.
12. http://www.cochranelibrary.com/. Accessed: 31 January 2018.
13. http://www.sign.ac.uk/. Accessed: 15 December 2017.
14. Papillon J, Montbarbon JF. Epidermoid carcinoma of the anal canal. A series of 276 cases. Dis Colon Rectum 1987; 30: 324-333.
15. Sandhu AP, Symonds RP, Robertson AG et al. Interstitial iridium-192 implantation combined with external radiotherapy in anal cancer: ten years’ experience. Int J Radiat Oncol Biol Phys 1998; 40: 575-581.
16. Weber DC, Kurtz JM, Allal AS. The impact of gap duration on local control in anal canal carcinoma treated by split-course radiotherapy and concomitant chemotherapy. Int J Radiat Oncol Biol Phys 2001; 50: 675-680.
17. Chapet O, Gerard JP, Riche B et al. Prognostic value of tumor regression evaluated after first course of radiotherapy for anal canal cancer. Int J Radiat Oncol Biol Phys 2005; 63: 1316-1324.
18. Doniec JM, Schniewind B, Kovács G et al. Multimodal therapy of anal cancer added by new endosonographic-guided brachytherapy. Surg Endosc 2006; 20: 673-678.
19. Bruna A, Gastelblum P, Thomas L et al. Treatment of squamous cell anal canal carcinoma (SCACC) with pulsed dose rate brachytherapy: a retrospective study. Radiother Oncol 2006; 79: 75-79.
20. Hannoun-Levi JM., Ortholan C, Resbeut M et al. High-dose split-course radiation therapy for anal cancer: outcome analysis regarding the boost strategy (CORS-03 study). Int J Radiat Oncol Biol Phys 2011; 80: 712-720.
21. Lestrade L, De Bari B, Pommier P et al. Role of brachytherapy in the treatment of cancers of the anal canal. Long-term follow-up and multivariate analysis of a large monocentric retrospective series. Strahlenther Onkol 2014; 190: 546-554.
22. Gryc T, Ott O, Putz F et al. Interstitial brachytherapy as a boost to patients with anal carcinoma and poor response to chemoradiation: Single-institution long-term results. Brachytherapy 2016; 15: 865-872.
23. Cordoba A, Escande A, Leroy T et al. Low-dose-rate interstitial brachytherapy boost for the treatment of anal canal cancers. Brachytherapy 2017; 16: 230-235.
24. Welton ML, Lambert R, Bosman FT. Tumors of the Anal Canal. In: Bosmqan FT, Carneiro F, Hruban RH, Theise ND (eds.). WHO Classification of tumors of the Digestive System. IARC, Lyon 2010; 183-193.
25. Pierquin B, Dutreix A, Paine CH et al. The Paris system in interstitial radiation therapy. Acta Radiol Oncol Radiat Phys Biol 1978; 17: 33-48.
26. Womack NR, Morrison JF, Williams NS. Prospective study of the effects of postanal repair in neurogenic faecal incontinence. Br J Surg 1988; 75: 48-52.
27. UKCCCR. Epidermoid anal cancer: results from the UKCCCR randomised trial of radiotherapy alone versus radiotherapy, 5-fluorouracil, and mitomycin. UKCCCR Anal Cancer Trial Working Party. UK Co-ordinating Committee on Cancer Research. Lancet 1996; 348: 1049-1054.
28. Bartelink H, Roelofsen F, Eschwege F et al. Concomitant radiotherapy and chemotherapy is superior to radiotherapy alone in the treatment of locally advanced anal cancer: results of a phase III randomized trial of the European organization for research and treatment of cancer radiotherapy and gastrointestinal cooperative groups. J Clin Oncol 1997; 15: 2040-2049.
29. Gunderson LL, Winter KA, Ajani JA et al. Long-term update of US GI intergroup RTOG 98-11 phase III trial for anal carcinoma: survival, relapse, and colostomy failure with concurrent chemoradiation involving fluorouracil/mitomycin versus fluorouracil/cisplatin. J Clin Oncol 2012; 30: 4344-4351.
30. Sodergren SC, Vassiliou V, Dennis K et al. Systematic review of the quality of life issues associated with anal cancer and its treatment with radiochemotherapy. Support Care Cancer 2015; 23: 3613-3623.
31. James RD, Glynne-Jones R, Meadows HM et al. Mitomycin or cisplatin chemoradiation with or without maintenance chemotherapy for treatment of squamous-cell carcinoma of the anus (ACT II): a randomised, phase 3, open-label, 2x2 factorial trial. Lancet Oncol 2013; 14: 516-524.
32. Peiffert D, Tournier-Rangeard L, Gérard JP et al. Induction chemotherapy and dose intensification of the radiation boost in locally advanced anal canal carcinoma: final analysis of the randomized UNICANCER ACCORD 03 Trial. J Clin Oncol 2012; 30: 1941-1948.
33. Saarilahti K, Arponen P, Vaalavirta L et al. The effect of intensity-modulated radiotherapy and high dose rate brachytherapy on acute and late radiotherapy-related adverse events following chemoradiotherapy of anal cancer. Radiother Oncol 2008; 87: 383-90.
34. Widder J, Kastenberger R, Fercher E et al. Radiation dose associated with local control in advanced anal cancer: Retrospective analysis of 129 patients. Radiother Oncol 2008; 87: 367-375.
35. Falk AT, Claren A, Benezery K et al. Interstitial high dose rate brachytherapy as boost for anal canal cancer. Radiat Oncol 2014; 9: 240-241.
36. Tagliaferri L, Manfrida S, Barbaro B et al. MITHRA – multi­parametric MR/CT image adapted brachytherapy (MR/CT-IABT) in anal canal cancer: a feasibility study. J Contemp Brachytherapy 2015; 7: 336-345.