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A national surveillance study of the current status of reirradiation using brachytherapy in Japan

Published:September 01, 2020DOI:https://doi.org/10.1016/j.brachy.2020.07.007

      Abstract

      Purpose

      This study aimed to explore the current status and pattern of practice for reirradiation using brachytherapy (ReRT-BT) through a survey in Japan.

      Materials and Methods

      We distributed an e-mail-based questionnaire to 153 institutions equipped with high-dose-rate brachytherapy facilities.

      Results

      We received responses from 76 institutions (49.7%). Forty-three of these institutions performed ReRT-BT and 42 institutions (55%) performed ReRT-BT during 2009–2018. However, 29 of the 42 institutions (69%) reported difficulty in obtaining ReRT-BT case information from their respective databases. Almost all the institutions encountered insufficient database system to extract details about the ReRT-BT cases. Responses from 33 institutions included the number of ReRT-BT cases; this increased from 90 in the period 2009–2013 (institution median = 0.5; 0–16) to 172 in the period 2014–2018 (institution median = 2; 0–26). Nine institutions had to perform ReRT-BT for more than one case per year. The major location for cancer treatment was the pelvis (94%), followed by the head and neck (5%) and others (1%). In six site-specific scenarios, barring uterine corpus cancer recurrence, more than 90% of radiation oncologists agreed to perform ReRT-BT, whereas other areas (head and neck, prostate, and rectal cancer) gained 16–37% agreement.

      Conclusions

      This decade saw an increase in the number of ReRT-BT cases in Japan and radiation oncologists’ interest in ReRT-BT as a viable therapeutic option. However, scarce availability, immature education system, and insufficient database system are barriers to further consensus building.

      Keywords

      Introduction

      Reirradiation (ReRT) has historically been associated with unacceptable toxicity in some cases and revealed limited benefit with a limited irradiated dose for tumor control. Therefore, for a long time, systemic therapies have often been considered in many cancers in cases of local failure when no local salvage therapy was even technically possible (
      • Jones B.
      • Blake P.R.
      Retreatment of cancer after radical radiotherapy.
      ). ReRT has a long history (
      • Jones B.
      • Blake P.R.
      Retreatment of cancer after radical radiotherapy.
      ,
      • Zuppinger A.
      Spätveränderungen nach protrahiert-fraktionierter Röntgenbestrahlung im Bereich der oberen Luft- und Speisewege.
      ,
      • Nieder C.
      • Langendijk J.A.
      • Guckenberger M.
      • et al.
      Preserving the legacy of reirradiation: a narrative review of historical publications.
      ), and it has gained increasing attention with advances in modern radiation techniques such as intensity-modulated radiation therapy (IMRT), stereotactic radiotherapy, and particle therapy (
      • Dörr W.
      • Gabryś D.
      The principles and practice of Re-irradiation in clinical oncology: an overview.
      ) because of higher tumor local control possibility than that with systemic therapy alone. Because brachytherapy (BT) was the initial radiotherapy (RT) equipment in RT history, we could find reports of ReRT using BT (ReRT-BT) with or without external-beam RT (EBRT) in the early 1930s (
      • Nieder C.
      • Langendijk J.A.
      • Guckenberger M.
      • et al.
      Preserving the legacy of reirradiation: a narrative review of historical publications.
      ). Scarce data made it difficult to build consensus about ReRT-BT; however, BT is the best conformal radiation treatment modality because it allows highest radiation dose escalation to the gross tumor volume, with a steep dose fall-off, thereby protecting the surrounding previously irradiated healthy organs. In addition, the recent image-guided BT technique has enabled us to treat tumors more precisely. To collect information about the actual ReRT-BT status in Japan, we performed a questionnaire survey among institutions with BT facility. The objective of this study was to conduct a survey on the current status of ReRT-BT and to determine its patterns of practice.

      Materials and methods

      A survey questionnaire (Supplementary file: questionnaire) was e-mailed to radiation oncologists (ROs) working in facilities equipped with the high-dose-rate BT equipment. [118 microSelectron (Elekta AB, Stockholm, Sweden), 8 VariSource (Varian Medical Co., PA), 27 MultiSource, or SagiNova (Eckert & Ziegler, Berlin, Germany)] as of 2018. In total, 153 institutions participated in the survey. At the time of correspondence, all respondents were actively practicing in the facilities in Japan. Part I of the survey questionnaire included questions on the actual number of ReRT-BT cases in 2018, 2017, 2016, 2009–2013, and 2014–2018 in both the total group and the subgroups by location. Part II included questions on the indications for Re-RT in six case scenarios involving the most common tumor types (head and neck, rectum, prostate, and gynecologic tumors). The completed questionnaires were received through e-mail. In this study, ReRT was defined as an RT performed after a previous session of RT of 30 Gy/10 fractions or more (= EQD2 36 Gy using α/β = 3, where EQD2 = equivalent 2-Gy fractions). A BED was calculated into EQD2 using the linear quadratic model: EQD2 = prescription dose × (α/β + dose per fraction)/(α/β + 2), where α/β = 10 for tumors and 3 for organs at risk. This study was conducted in accordance with the Declaration of Helsinki and with institutional review board permission (ERB-C-1330-1) of Kyoto Prefectural University of Medicine.

      Statistical analysis

      All statistical analyses were performed using StatView 5.0 statistical software (SAS Institute, Inc., Cary, NC). The percentage values were analyzed using the χ2 test, and values were compared using Mann-Whitney U analysis. p < 0.05 was considered to indicate statistical significance for all analyses.

      Results

      We received responses from 76 institutions (76/153 = 49.7%; 67 microSelectron, five VariSource, four MultiSource or SagiNova). Forty-three of 76 institutions (57%) performed ReRT and 42 (55%) institutions performed ReRT-BT during 2009–2018. Thirteen institutions could extract ReRT-BT case details without difficulty. However, 29 of the 42 institutions (69%) reported difficulty in obtaining ReRT-BT case information from their respective databases. Only nine institutions had a database system that contained the “head word” or “item” [ReRT] and almost all the institutions encountered insufficient database system to extract details about the ReRT-BT cases.
      Responses from 33 institutions included the number of ReRT-BT cases (Table 1); this increased from 90 in the period 2009–2013 (institution median = 0.5; 0–16) to 172 in the period 2014–2018 (institution median = 2; 0–26). Fig. 1 shows the number of ReRT-BT cases encountered in the institutions in 10 years. Nine institutions (9/33 = 28%) performed ReRT-BT for more than one case per year. The pelvis was the major location treated (209/223 = 94%), followed by the head and neck (11 = 5%), and others (3 = 1%) (Table 1).
      Table 1Characteristics of institutions treated with reirradiation using brachytherapy
      a) Patients number treated with reirradiation using brachytherapy during 2009–2013 and 2014–2018
      2009–2013(%)2014–2018(%)
      (5 years)(5 years)
      Total number90133
      Head and neck1(1%)10(8%)
      Pelvis89(99%)120(90%)
      Other0(0%)3(2%)
      Summation of number does not equal because of duplicated or incomplete answers.
      b) Details of patients number treated during 2016–2018
      2016(%)2017(%)2018(%)
      (Single year)(Single year)(Single year)
      Total number354251
      Head and neck2(6%)2(5%)4(8%)
      Pelvis29(83%)39(93%)47(92%)
      Other1(3%)1(2%)0(0%)
      HDR22(67%)33(83%)42(88%)
      LDR11(33%)7(18%)6(12%)
      Summation of number does not equal because of duplicated or incomplete answers.
      LDR = low-dose-rate brachytherapy; HDR = high-dose-rate brachytherapy.
      Figure thumbnail gr1
      Fig. 1Number of institutions according to experienced ReRT-BT cases per 10 years. ReRT-BT = reirradiation using brachytherapy.

      Responses for site-specific case scenarios

      The ROs were presented with six different clinical scenarios (supplemental reference) and asked a series of questions regarding how they would manage them. Sixty-two ROs responded to the site-specific questions, as summarized in Table 2.
      Table 2Attitude to ReRT in specified case scenarios
      Case no.ROs answerCommentMethods and BT ratio
      YesNoUnc(%) Of ReRT

      Yes
      Recommended modalitiesDetailed scheduleReRT-BT

      Yes
      (%) Of ReRT-BT in ReRT(%) Of ReRT-BT in whole
      1Tongue cancer Pre: Surgery + PORT44161(72%)OP∗,

      ICI
      3D-CRT: 12, IMRT: 26, BT 11, SRT: 7, proton beam radiotherapy: 1, BNCT: 1, EBRT + ia: 23D-CRT, IMRT: 10–70 Gy/1–50 fr

      LDR-BT 60 Gy

      HDR: 45.5 - 48 Gy/7–8 fr bid, 10 Gy/1fr
      11(25%)(18%)
      2Rectal cancer

      Pre: PreRT + surgery
      5830(95%)Predominantly palliative2D: 1, 3DCRT: 15, IMRT:34, BT:16, SRT: 8, particle therapy: 53D-CRT: 20–60 Gy/10–30 fr

      IMRT: 45–60 Gy/18–30 fr

      Particle therapy: 60–66 Gy/30~33 fr

      HDR: 32–49/7–8 fr bid
      16(28%)(26%)
      3Cervical cancer

      Pre: CRT
      28340(45%)OP∗3D-CRT: 3, IMRT:5, BT:23, SRT:2IMRT: 15–30.6 Gy/3–17 fr

      SBRT: 42 Gy/6 fr

      HDR: 24–48/4–8 fr bid
      23(82%)(37%)
      4Endometrioid cancer

      Pre: surgery + PORT
      6010(98%)HDR: 58, IMRT: 8IMRT: 30–50 Gy/15–25 fr

      HDR-BT: 20–48 Gy/4–8 fr bid
      58(97%)(95%)
      5Prostate Ca.

      Pre: BT (LDR)
      32282(52%)ADT, OP∗3D-CRT: 2, IMRT: 10, BT: 18 (LDR 5, HDR 5), SRT 53D-CRT~IMRT: 45–80 Gy/25–40fr

      SBRT: 36.25 Gy/5fr

      LDR: 110–145 Gy

      HDR: 20–45.5 Gy/2–7fr bid
      18(56%)(29%)
      6Prostate Ca.

      Pre: IMRT
      23340(40%)ADT, OP∗IMRT: 4, BT: 18 (8LDR, 6HDR), SRT: 2SBRT: 30–36.25 Gy/5fr

      LDR: 110–160 Gy

      HDR: 40–45.5 Gy/4–7fr bid
      18(78%)(32%)
      Summation of % dose not equal 100% because of duplicated answers or unspecified answers.
      BT = brachytherapy; LDR = low-dose-rate; HDR = high-dose-rate; Unc = uncertain; Pre = previous treatment; SRT = stereotactic body irradiation; 2D = two-dimensional radiotherapy; 3D-CRT = three-dimensional conformal radiotherapy; IMRT = intensity-modulated radiotherapy; CRT = chemoradiotherapy; PORT = postoperative radiotherapy; PreRT = preoperative radiotherapy; ADT = androgen deprivation therapy; OP∗ = surgery first if possible; BNCT = boron neutron capture therapy; ia = intra-arterial chemotherapy; ReRT-BT = reirradiation using brachytherapy.

      Case 1: Tongue cancer

      A 55-year-old man with a local recurrence of tongue cancer after surgery and postoperative RT (60 Gy/30 fractions). Seventy-two percent of ROs agreed to ReRT in case of an unresectable situation (7 ROs specified for palliative intention). IMRT (26/44 = 59%) is a major technique to use for ReRT, and 18% ROs chose BT as a modality.

      Case 2: Rectal cancer

      A 45-year-old man with a local recurrence (3 × 2 cm) after preoperative chemoradiotherapy (50 Gy/25fr) and surgery 3 years later. He complained of pain in the buttocks and refused to undergo operation. Ninety-five percent of ROs agreed to ReRT, and 26% chose ReRT-BT.

      Case 3: Cervical cancer

      A 63-year-old woman with a local recurrence of Stage IIB cervical cancer who received curative RT (whole pelvis 50 Gy/25 fractions and intracavitary irradiation of 30 Gy/4fr) 12 months before. Forty-five percent of ROs agreed to ReRT, but only 37% chose BT.

      Case 4: Endometrial cancer

      A 56-year-old woman with a history of endometrial cancer treated with surgery, followed by adjuvant RT (45 Gy/25 fractions using 3D-CRT) who developed in-field vaginal cuff recurrence. In this case, nearly all ROs (98%) would offer retreatment and 95% would retreat with a BT.

      Cases 5 and 6: Prostate cancer

      The two different scenarios that just changed the prior treatment (EBRT or BT) were presented. In the setting of prior BT, 52% ROs would offer retreatment with RT and 29% chose BT. In the setting of prior EBRT, 40% of ROs would offer retreatment with RT, whereas 32% would consider retreatment with BT.
      In those site-specific scenarios, 40–98% ROs recommended ReRT, and most (95%) ROs recommended ReRT-BT for endometrioid cancer case, as compared with few (18%) ROs who recommended ReRT-BT for tongue cancer.

      Discussion

      The aim of this study was to conduct a survey on the current status of ReRT-BT in Japan. More than half of the institutions responded that they performed ReRT-BT (55%) in this decade, and the ReRT-BT number increased from 90 in the period 2009–2013 (institution median = 0.5; 0–16) to 172 in the period 2014–2018 (institution median = 2; 0–26). However, only nine institutions (9/76 = 12%) experienced ReRT-BT for more than one case per year, which imply the scarce resource and information of ReRT-BT in Japan. Our data provide useful information of ReRT-BT not only for ROs but also for physicians treating cancer.
      As BT offers one of the best dose distributions in radiotherapy: a high radiation dose to the target volume while better protecting surrounding previously irradiated healthy tissues. Many studies describe BT as a ReRT equipment in local recurrences of previously irradiated prostate (
      • Ingrosso G.
      • Becherini C.
      • Lancia A.
      • et al.
      Nonsurgical salvage local therapies for radiorecurrent prostate cancer: a systematic review and meta-analysis.
      ), gynecological (
      • Sturdza A.
      • Viswanathan A.N.
      • Erickson B.
      • et al.
      American Brachytherapy Society working group report on the patterns of care and a literature review of reirradiation for gynecologic cancers.
      ,
      • Raziee H.
      • D'Souza D.
      • Velker V.
      • et al.
      Salvage Re-irradiation with single-modality interstitial brachytherapy for the treatment of recurrent gynaecological tumours in the pelvis: a multi-institutional study.
      ,
      • Sadozye A.H.
      Re-irradiation in gynaecological malignancies: a review.
      ,
      • Umezawa R.
      • Murakami N.
      • Nakamura S.
      • et al.
      Image-guided interstitial high-dose-rate brachytherapy for locally recurrent uterine cervical cancer: a single-institution study.
      ,
      • Yoshida K.
      • Yamazaki H.
      • Nakamura S.
      • et al.
      Re-irradiation using interstitial brachytherapy increases vaginal mucosal reaction compared to initial brachytherapy in patients with gynecological cancer.
      ), breast (
      • Hannoun-Lévi J.M.
      • Resch A.
      • Gal J.
      • et al.
      Accelerated partial breast irradiation with interstitial brachytherapy as secondconservative treatment for ipsilateral breast tumor recurrence: multicen-tric study of the GEC-ESTRO Breast Cancer Working Group.
      ), head and neck (
      • Hegde J.V.
      • Demanes D.J.
      • Veruttipong D.
      • et al.
      Head and neck cancer reirradiation with interstitial high-dose-rate brachytherapy.
      ,
      • Breen W.
      • Kelly J.
      • Park H.S.
      • et al.
      Permanent interstitial brachytherapy for previously irradiated head and neck cancer.
      ,
      • Yamazaki H.
      • Yoshida K.
      • Yoshioka Y.
      • et al.
      High dose rate brachytherapy for oral cancer.
      ), rectal cancers (
      • Mohiuddin M.
      • Marks G.
      • Marks J.
      Long-term results of reirradiation for patients with recurrent rectal carcinoma.
      ), brain tumor (
      • Wick W.
      • Fricke H.
      • Junge K.
      • et al.
      A phase II, randomized, study of weekly APG101+reirradiation versus reirradiation in progressive glioblastoma.
      ), sarcoma (
      • Sanmamed N.
      • Berlin A.
      • Beiki-Ardakani A.
      • et al.
      Magnetic resonance imaging-guided brachytherapy Re-irradiation for isolated local recurrence of soft tissue sarcoma.
      ), or secondary primary cancers (
      • Quivrin M.
      • Peignaux-Casasnovas K.
      • Martin É.
      • et al.
      Salvage brachytherapy as a modern reirradiation technique for local cancer failure: the Phoenix is reborn from its ashes.
      ) occurring in-field. Generally, current data confirm that BT ReRT is feasible and has acceptable toxicity (
      • Quivrin M.
      • Peignaux-Casasnovas K.
      • Martin É.
      • et al.
      Salvage brachytherapy as a modern reirradiation technique for local cancer failure: the Phoenix is reborn from its ashes.
      ).
      The prognosis and therapeutic intention vary depending on the type and location of primary cancer. Local recurrence of breast (
      • Ingrosso G.
      • Becherini C.
      • Lancia A.
      • et al.
      Nonsurgical salvage local therapies for radiorecurrent prostate cancer: a systematic review and meta-analysis.
      ) or prostate cancer (
      • Hannoun-Lévi J.M.
      • Resch A.
      • Gal J.
      • et al.
      Accelerated partial breast irradiation with interstitial brachytherapy as secondconservative treatment for ipsilateral breast tumor recurrence: multicen-tric study of the GEC-ESTRO Breast Cancer Working Group.
      ) could expect long life expectancy, and therefore, an individualized curative approach is recommended to maintain the patients’ quality of life. On the other hand, local recurrence of head and neck (
      • Hegde J.V.
      • Demanes D.J.
      • Veruttipong D.
      • et al.
      Head and neck cancer reirradiation with interstitial high-dose-rate brachytherapy.
      ,
      • Breen W.
      • Kelly J.
      • Park H.S.
      • et al.
      Permanent interstitial brachytherapy for previously irradiated head and neck cancer.
      ,
      • Yamazaki H.
      • Yoshida K.
      • Yoshioka Y.
      • et al.
      High dose rate brachytherapy for oral cancer.
      ) and brain cancers (
      • Wick W.
      • Fricke H.
      • Junge K.
      • et al.
      A phase II, randomized, study of weekly APG101+reirradiation versus reirradiation in progressive glioblastoma.
      ) often has a grim prognosis, with anticipating comorbidities resulting in rather palliative intension to hinder the active management.
      ROs should make difficult clinical decisions depending on their own experiences and paucity of good-quality evidence of ReRT, especially for ReRT-BT, which are based on a number of questions: i) normal tissue tolerability (
      • Nieder C.
      • Milas L.
      • Ang K.K.
      Tissue tolerance to reirradiation.
      ,
      • Nieder C.
      Second re-irradiation: a delicate balance between safety and efficacy.
      ), ii) availability of the technical data of the first RT allowing a ReRT, iii) choice of either for palliative or for radical intention including prognosis should depend on the site and cancer histopathology, iv) ReRT-BT schedule and dose fractionation–volume relationship, etc. Such treatment decisions must be handled only by teams with expertise in BT and implemented in carefully selected patients.
      With the advent of technology, there are many types of high-precision RT techniques that patients could benefit from: stereotactic RT, proton therapy, and BT (low-, high-, or pulsed-dose-rate). Advances in external RT with IMRT and image-guided radiation therapy have significantly reduced toxicities and improved outcomes. As a result, use of BT alone or as a boost has diminished over the last decades (
      • Fischer-Valuck B.W.
      • Gay H.A.
      • Patel S.
      • et al.
      A brief review of low-dose rate (LDR) and high-dose rate (HDR) brachytherapy boost for high-risk prostate.
      ,
      • Schad M.D.
      • Patel A.K.
      • Glaser S.M.
      • et al.
      Declining brachytherapy utilization for cervical cancer patients – have we reversed the trend?.
      ). However, IMRT or stereotactic RT, although highly conformal, is not significantly better than BT in their ability to spare the surrounding previously irradiated tissues (
      • Dörr W.
      • Gabryś D.
      The principles and practice of Re-irradiation in clinical oncology: an overview.
      ,
      • Nieder C.
      • Milas L.
      • Ang K.K.
      Tissue tolerance to reirradiation.
      ).
      Several salvage BT techniques are available: ultralow-dose-rate with iodine-125 (125-I) seeds or now-obsolete low-dose-rate BT with iridium-192 (192-Ir) wires, or high-dose-rate with cobalt-60 (60-Co) or 192-Ir or pulsed-dose-rate with 192-Ir. However, we could not find any difference in the comparison among BT techniques thus far. At present, the BT technique may be solely used depending on the available utility and ROs’ experiences (
      • Quivrin M.
      • Peignaux-Casasnovas K.
      • Martin É.
      • et al.
      Salvage brachytherapy as a modern reirradiation technique for local cancer failure: the Phoenix is reborn from its ashes.
      ). This would likely highlight that experience could lead to more utilization of BT ReRT, as it is likely the responders who have high-level experience with BT would be more likely to perform BT.
      We noticed that ReRT-BT is a relatively new category identified, and the presently available database system does not meet the needs to extract ReRT-BT case details, especially ReRT-BT cases performed in most institutions. Almost all the institutions encountered difficulty in retrieving ReRT-BT case information. Some institutions examined the data for all patients who received RT twice or more, to identify the overlap between previous RT fields and the ReRT-BT field. An efficient database system for ReRT-BT case information retrieval is essential for future exploration of ReRT-BT utility.
      ReRT-BT cases increased in number from 2009–2013 to 2014–2018, indicating that ROs are more familiar about using ReRT-BT recently. This may have been because RT technology use has considerably improved during this decade, and more patients recently received ReRT-BT using state-of-the-art equipment. However, only 14 institutions (18.4% of answered institutions) experienced ReRT-BT more than equal one case per year. In general, BT utility decreased in number even for fresh case for several reasons; i) lower renumeration than advanced EBRT, ii) training and experience, iii) advanced technique in EBRT, iv) patients’ perspective (
      • Kirthi Koushik A.S.
      • Alva R.C.
      Brachytherapy in head and neck cancers: "are we doing it or are we done with it.
      ). The ROs who have the proficiency to perform BT, especially interstitial BT, seem to be inadequate in number because the technique requires training and expertise for optimal applications. In many cancer centers, the caseload is insufficient to provide this experience. As a result, there is limited opportunity for the general oncologic society to have enough education about ReRT-BT. The American Brachytherapy Society has started a “300 in 10” initiative to increase the training of brachytherapists by assisting in the training of 30 oncologists per year over a 10-year period (
      • Fischer-Valuck B.W.
      • Gay H.A.
      • Patel S.
      • et al.
      A brief review of low-dose rate (LDR) and high-dose rate (HDR) brachytherapy boost for high-risk prostate.
      ), which reflected the status of the present brachytherapy society. Enough experience could lead to more utilization of BT ReRT, as it is likely the responders who have high-level experience with BT would be more likely to perform BT.
      The pelvis is a major site for ReRT-BT in the Japanese cohort. It is natural because gynecological and prostate lesions could be good candidates not only for fresh BT but also for ReRT-BT with accumulated evidence (
      • Ingrosso G.
      • Becherini C.
      • Lancia A.
      • et al.
      Nonsurgical salvage local therapies for radiorecurrent prostate cancer: a systematic review and meta-analysis.
      ,
      • Sturdza A.
      • Viswanathan A.N.
      • Erickson B.
      • et al.
      American Brachytherapy Society working group report on the patterns of care and a literature review of reirradiation for gynecologic cancers.
      ,
      • Raziee H.
      • D'Souza D.
      • Velker V.
      • et al.
      Salvage Re-irradiation with single-modality interstitial brachytherapy for the treatment of recurrent gynaecological tumours in the pelvis: a multi-institutional study.
      ,
      • Sadozye A.H.
      Re-irradiation in gynaecological malignancies: a review.
      ,
      • Umezawa R.
      • Murakami N.
      • Nakamura S.
      • et al.
      Image-guided interstitial high-dose-rate brachytherapy for locally recurrent uterine cervical cancer: a single-institution study.
      ). However, the fact that low-volume head neck tumor could be a good candidate to curative ReRT-BT is well documented and has a long history (
      • Hegde J.V.
      • Demanes D.J.
      • Veruttipong D.
      • et al.
      Head and neck cancer reirradiation with interstitial high-dose-rate brachytherapy.
      ,
      • Breen W.
      • Kelly J.
      • Park H.S.
      • et al.
      Permanent interstitial brachytherapy for previously irradiated head and neck cancer.
      ,
      • Yamazaki H.
      • Yoshida K.
      • Yoshioka Y.
      • et al.
      High dose rate brachytherapy for oral cancer.
      ,
      • Kirthi Koushik A.S.
      • Alva R.C.
      Brachytherapy in head and neck cancers: "are we doing it or are we done with it.
      ); however, fewer cases are salvaged by ReRT-BT in Japan. This is because insufficient information and resource prevent physicians and patients from accessing experienced high-volume BT centers, in which they could have increasing opportunities to undergo treatment using ReRT-BT. We speculate that those patients can lose the opportunity to be cured. The development of a national database or registry for clinical use and multicenter collaborative data sharing would provide quality data to analyze ReRT-BT outcomes in terms of disease control and treatment toxicity and develop guidelines. Consensus guidelines should be written and published.

      Conclusions

      In conclusion, this decade saw an increase in the number of ReRT-BT cases in Japan and ROs’ interest in ReRT-BT as a viable therapeutic option. However, scarce availability and immature education system and insufficient database system are the barriers to further consensus building.

      Acknowledgments

      The authors acknowledge the collaboration of many radiation oncologists in Japan. This study was supported by grant-in-aid for research on radiation oncology of Japanese Society for Radiation Oncology (JASTRO) 2018-2020.
      JBReRT group∗;
      ∗Japan brachytherapy ReRT group included Shinichiro Toshima, Atsunori Yorozu, Kiyokazu Sato, Keishiro Suzuki, Natsumi Futakami, Jyuniti Omagari, Ryosuke Hara, Shuji Ohtsu, Keiichiro Koiwai, Keiji Matsumoto, Keiko Murofushi, Masahiro Tanaka, Satoshi Itasaka, kazuo Kusuhara, Hideki Obara, Yuuta Sato, Chisato Hata, Yoshiyuki Hiraki Takuya Yamazaki, Hidekazu Tanaka, Hitoshi Ikushima, Yuki Mukai, Ryosuke Takenaka, Norihisa Katayama, Yoshio Tamaki, Yasushi Hamamoto, Mayumi Harada, Kenta Konishi, Kouichi Inoue, Rumiko Kinoshita, Nobuhiko Kamiya, Mayumi Omoteda, Mariko Kawamura, Yuta Shibamoto, Shunichi Ishihara, Yoshiteru Nakashima, Aya Nakajima, Kenji Takayama, Ryuta Nagao, Hiromitsu Endo, Tomoki Tanaka, Noriko Ii, Saiji Ohga, Takeaki Kusada, Ikuno Nishibuchi, Hiroyuki Tachibana, Daisuke Nakamura, Hirofumi Kuwabara, Daisuke Higashino, Rei Umezawa, Masaaki Kataoka Naonobu Kunitake, Tadashi Sugita, Kayoko Tsujino, Nobuki Imano, Koji Konishi, Sachiko Izumi, Masayuki Matsuo, Yuko Kaneyasu, Kazuyoshi Takei, Hiroaki Kunogi, Toshiyuki Imagunbai, Naoya Murakami, MItsunobu Igari, Yu Okubo, Isao Asakawa, Naoya Ishibashi, Keiichi Jingu, Yoshiomi Hatayama, Etsuyo Ogo, Takashi Uno, and Mitsutoshi Oishi.

      Supplementary data

      References

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