The results of this survey indicate that radiotherapy is used as a treatment option for anal HSIL among German radiation oncologists. Indeed, 64% of respondents indicated having received treatment requests, and 50% had administered radiotherapy for HSIL and reported good or very good overall results. Patients are referred by surgeons and proctologists in cases of recurrence and a lack of alternative treatment methods. Radiation oncologists (64%), however, considered radiotherapy a valuable option for recurrences in particular, where concerns about postoperative complications or anorectal functional deterioration with further non-radiotherapeutic treatments dominate the patients’ concerns.

Chemoradiotherapy represents the current standard of treatment for local and locally advanced SCCA, with good tumor control rates and enablement of organ preservation [7, 16]. Beyond invasive cancers, radiotherapy has demonstrated efficacy in treating various precancerous lesions due to its capacity to target atypical, genetically unstable cells [17, 20]. Although carcinomas in situ lack invasive potential, they exhibit cellular features akin to malignancy, such as elevated proliferation rates and genetic instability, making them particularly responsive to the DNA-damaging effects of radiation [21, 22]. In a large meta-analysis involving 3729 women with breast-conserving surgery for ductal carcinoma in situ (DCIS), adjuvant radiotherapy was shown to significantly reduce the absolute 10-year risk of any ipsilateral breast event (either DCIS or invasive cancer) by 15.2% (SE 1.6%, reducing the risk from 28.1% to 12.9%; P < 0.00001). This reduction was consistent across various patient and treatment characteristics [17]. Consequently, radiotherapy is widely employed for DCIS of the breast [23, 24]. Radiotherapy is also highly effective for germ cell neoplasia in situ of the testis (GCNIS) due to its high radiosensitivity, as demonstrated in multiple studies [20, 25, 26]. For GCNIS limited to a single testicle, localized radiotherapy with doses of 18–20 Gy achieves eradication of GCNIS cells in over 95% of cases [20, 27]. Radiotherapy has been proven to be an effective treatment for local control in other precancerous lesions. However, only retrospective evaluations exist for most entities. In laryngeal dysplasia, durable control and maintained long-term functionality could be shown, despite acute toxicity in some cases [18]. In a retrospective monocentric series of 23 patients who had received radiotherapy for laryngeal precancerous lesions (mainly 60 Gy within 6 weeks with a fractionation of 4 × 2.5 Gy per week), only one patient showed a definite recurrence after a follow-up of at least 3 years [28]. For Bowen’s disease, Herman JM et al. demonstrated that definitive radiotherapy (RT) achieves high rates of local tumor control with minimal morbidity. The study included 9 patients with BD who received RT between 1999 and 2004, encompassing a total of 14 digit lesions. Treatment involved photon irradiation while the lesions were immersed in a water bath, with a median delivered dose of 50 Gy (range 25–66 Gy) in fractions of 2.5 Gy (range 2–3 Gy). After a median follow-up of 25 months (range 0.4–52 months), all lesions remained locally controlled. Acute side effects were mostly mild to moderate erythema, desquamation, or edema (grade 1–2) that resolved within 1 month [29]. Further studies have also demonstrated the strong effectiveness of radiotherapy in Bowens disease, although careful patient selection is considered essential [19, 30,31,32].

According to the experience of the study participants, the treatment outcomes (with adequate follow-up) were described as good or very good. This is in line with initial publications on the efficacy of radiotherapy for anal HSIL, showing promising results in this setting. Howard et al. reported a 96% 5‑year local control rate for 31 patients with AIN III treated with moderate-dose radiotherapy, with minimal acute treatment interruptions [33]. Ortholan et al. (2005) similarly demonstrated long-term tumor control in Tis-stage or T1N0 anal canal carcinoma treated with adjuvant or salvage radiation, thereby underscoring radiotherapy’s potential as an effective option for HSIL in cases resistant to other treatments [34]. Even though these data are promising, it must be emphasized that radiotherapy is not a standard treatment for anal HSIL at the current time, particularly due to the limited available evidence. However, it is noteworthy that the recently published German-Austrian guidelines on anal dysplasia and anal cancer in HIV-positive individuals (S2k) have already acknowledged radiotherapy as a potential option, explicitly stating that it “may be considered in exceptional cases” [35].

Alongside the excellent control rates, factors such as toxicity rates and overarching treatment strategies warrant consideration. Experience with radiotherapy for SCCA shows that despite advancements in intensity-modulated radiotherapy (IMRT) and an improved side effect profile, significant acute skin toxicities can still occur. In a prospective phase II study investigating IMRT for anal carcinoma, Kachnic et al. demonstrated that IMRT significantly reduced grade 3+ dermatological side effects compared to historical controls (RTOG 8911), with rates of 23% versus 49% [36]. However, in radiotherapy for SCCA, the target volume encompasses the pelvic and inguinal lymphatic drainage areas, resulting in a considerably larger irradiated skin volume that includes the sensitive groin region. Additionally, concurrent chemotherapy is administered, which further exacerbates side effects. The vast majority of survey participants (95%) did not consider inclusion of lymphatic drainage areas or concurrent chemotherapy necessary for HSIL treatment. Radiodermatitis can now be effectively managed, typically healing completely, suggesting that higher-grade side effects are likely to remain within a manageable range and can be well controlled. Another critical consideration is that should radiotherapy for anal HSIL prove unsuccessful and a secondary anal carcinoma subsequently develop, standard chemoradiotherapy may no longer be feasible or may only be possible with heightened toxicity. However, the likelihood of such an outcome is considered to be very low.

Overall, patients with recurrent anal HSIL often endure significant physical and psychological distress due to the disease and the frequently repeated local therapies. During and after initial treatment difficulties (mainly temporary) with defecation, as well as pain, burning, and itching, which can lead to impaired sexual function, ranges between 61% and 100% [11, 12, 37,38,39,40,41]. It is therefore essential to provide these patients with effective treatment options. Guidelines currently lack specific recommendations for managing recurrent HSIL cases. [11,12,13,14,15]. As such, unsurprisingly, > 90% of participants in the the survey indicated a clinical study to be necessary to evaluate the effectiveness and tolerability of radiotherapy in patients with anal HSIL, especially in the recurrent setting.

The primary limitation of this study is the potential bias toward participants who already have experience with inquiries or treatments for anal HSIL, which may skew the overall representation of perspectives within the radiation oncology community in Germany.