Therapeutic effects of adjuvant brachytherapy in patients with resectable keloids

Introduction

Keloids are abnormal scars that develop due to an increased tissue response to dermal injury. They manifest through fibroblast proliferation and heightened collagen synthesis within the dermal and adjacent subcutaneous tissues. Unlike normal scars, keloids are prone to extend beyond the initial site of injury. Many patients experience bothersome symptoms such as pain and itching, along with cosmetic challenges, particularly in the case of large keloids (1,2).

Currently, a variety of treatment modalities are available for managing keloids (2-5). Non-surgical management of keloids includes intralesional corticosteroids, silicone gel sheeting, local administration of fluorouracil, and radiotherapy (RT) (6-9). Surgical interventions encompass cryotherapy and excision (6-9). The most significant limitation of surgery alone for keloid treatment is the high recurrence rate, making adjuvant therapies, such as RT essential. Additionally, some extensive keloid lesions are not suitable for surgical intervention and may be considered unresectable.

Lesions treated solely through surgical methods display recurrence rates ranging from 45% to 100% (10). Surgical interventions are regarded as inducing additional skin trauma, potentially causing more harm than the initial damage. Consequently, the global recommendation of combination therapy involving surgery and additional postoperative treatments has gained popularity.

Since 1906, numerous studies have provided substantial evidence supporting the efficacy of radiation therapy following the excision of keloids. Many RT techniques have been introduced for the treatment of keloids: electron beam, orthovoltage X-ray, megavoltage X-ray, and brachytherapy. The choices of treatment planning and type of radiation are typically based on physician’s experience and contingent upon institutional resources (10-15). However, there is no universally established approach for postoperative RT following keloid excision.

In certain cases, especially with keloids situated on curved surfaces, brachytherapy using a surface mould or flap may present an advantageous modality from both dosimetric and planning perspectives compared to external beam radiotherapy (EBRT) (11-15). The utilization of computer-based treatment planning facilitates the achievement of an optimized dose distribution (16-19). Besides, the rapid decrease in dose beyond the radioactive source potentially enables improved local control and preserves surrounding normal tissues, thereby reducing the risk of keloid regrowth.

Our study provides an initial report on the use of surface mould brachytherapy as adjuvant treatment for resectable keloids, with valuable insights into the practicality and clinical applicability of this approach, particularly within the context of real-world practice where RT timing and resource limitations may vary. Through a retrospective review of our institution’s experience, we explore the effectiveness of this technique and its potential advantages in treating keloids following surgical excision. This study aims to add to the existing literature by sharing our institutional findings, helping to broaden the understanding and potential application of brachytherapy as an adjuvant treatment for keloids. We present this article in accordance with the STROBE reporting checklist (available at https://tro.amegroups.com/article/view/10.21037/tro-24-16/rc).

Methods

Patient collection and treatment

This retrospective cohort study includes data from patients treated at National Cheng Kung University Hospital (NCKUH) between 2015 and 2022. Only patients diagnosed with keloids who had not previously undergone surgery or radiation therapy were included in the study. Patients with recurrent keloids or a history of prior radiation therapy to the lesion were excluded. We identified six patients with a total of 10 keloid lesions who underwent surgical excision followed by superficial mould brachytherapy. All patients had received previous treatments prior to excision, with intralesional steroid injections being the most common therapeutic intervention.

Patients with resectable keloids initially underwent surgical excision at our institution (20-22). The skin was primarily reconstructed using a tension-reduction suture technique, comprising two layers of robust suture material applied to the deep and superficial fascial layers to bring the wound edges closer. Through this method, the following dermal and epidermal sutures were seamlessly placed without tension, thereby minimizing tension strength on the dermal layer and decreasing the risk of keloid recurrence.

RT

In all cases, treatment involved the superficial application of brachytherapy (Figure 1) (24-26), with radiation initiation occurring within 1 to 6 weeks (median: 2 weeks) of surgery. After keloid excision, the wound typically transforms into a linear shape, replacing its original irregular or non-linear form. The highest risk of keloid recurrence generally occurs near the surgical wound, which guided our design of the treatment field and length to cover the surgical bed. Surface mould brachytherapy was employed by placing a small, flexible plastic tube (Freiberg flaps), positioned over the wound after scar removal. This soft plastic tube can be easily molded to conform to the surgical wound, ensuring optimal dose coverage. A radiation dose of 20 Gy in 4 fractions at 3 mm depth from the skin surface was delivered to the postoperative scar.

Figure 1 Image of a patient (A) after right shoulder keloids excision. The severity of keloid was evaluated by JSW Scar Scale (23). (B) Surface brachytherapy carriers, Freiberg flaps, were placed on the surface of the wound. (C) This tube can be easily shaped to conform to the surgical wound, ensuring optimal dose coverage. (D) The delivery of radiation was performed using HDR after loaders, employing an Ir-192 source. The radiation therapy treatment planning was performed using the Oncentra Brachy planning system (version 4.5.3, Nucletron). HDR, high dose rate; JSW, Japan Scar Workshop.

Brachytherapy was performed using high dose rate (HDR) afterloaders, employing an Ir-192 source, and the nominal treatment dose was calculated according to the guidelines outlined by the American Association of Physicists in Medicine Task Group No. 43 (AAPM TG-43). Radiation therapy treatment planning was conducted using the Oncentra Brachy planning system (version 4.5.3, Elekta Nucletron) (27).

Evaluation

The severity of keloid was assessed using the Japan Scar Workshop (JSW) Scar Scale (23) and the Vancouver Scar Scale (VSS) (23,25,28). Pain and itch were recorded via a Visual Analogue Scale (VAS). Preoperative VSS and JSW scores were recorded prior to surgery, while postoperative VSS and JSW scores were obtained at the last follow-up visit. The assessment process began with the initial evaluation before treatment and continued throughout follow-up visits after the completion of brachytherapy. Our follow-up protocol involved long-term observation period following radiation therapy. Patients visited the radiation oncologists and dermatologists every 3 months, and photographic documentation of keloid lesions was taken at each visit. Radiation side effects were assessed according to Common Terminology Criteria for Adverse Events (CTCAE) 4.0 guidelines. Evaluation of the three scales, treatment-related side effects, and cosmesis was conducted by two dermatologists and two radiation oncologists, each with over 15 years of experience in treating keloids. Additionally, patient follow-up status and treatment outcomes were discussed collaboratively in combined meetings.

Statistics

The Wilcoxon signed-rank test was applied to evaluate differences in three outcomes: changes in VSS scores (post- vs. pre-RT), VAS scores (post- vs. pre-RT), and JSW scores (post- vs. pre-RT). To account for the potential impact of multiple score values within the same lesion, statistical inference was conducted utilizing a generalized estimating equations (GEEs) model. All P values were computed as two-tailed, with statistical significance defined as P<0.05. The statistical analyses were carried out using R (version 4.3.3).

Ethical considerations

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of NCKUH (No. B-ER-113-130) and individual consent for this retrospective analysis was waived.

Results

Between January 2015 and December 2022, a total of 10 keloid lesions from six patients underwent excision followed by superficial brachytherapy at National Cheng Kung University Hospital (Table 1). All patients completed the prescribed treatment. The median age of the patients was 29 years (range, 23–60 years). The follow-up period ranged from 1.4 to 3.3 years (median, 2.3 years). Four out of six patients presented with multiple lesions, indicating significant disease activity. The average JSW classification was 19.5, suggesting a high prevalence of the keloid phenotype.

Among the 10 lesions being treated, most of the lesions were located on the mandible (4 patients), with additional occurrences on the chest wall (2 patients), shoulder (2 patients), and suprapubic region (2 patients). Table 2 shows the characteristics of these keloid lesions. All treated sites achieved both local control and satisfactory cosmesis, with no recurrences observed till the last follow-up day. Representative cases before excision and after brachytherapy are demonstrated in Figure 2 and Figure 3. Regarding the outcome of the difference (post- vs. pre-RT) in VSS, VAS and JSW scores, the reduction in median VSS scores (from 11 to 1, P=0.002), VAS scores (from 5 to 0, P=0.002), and JSW scores (from 11 to 1, P=0.002) demonstrated significant improvement in both pain levels and scar severity (Table 3).

Figure 2 Image of a patient before (A-C) keloids excision and surface HDR brachytherapy. After 2 years of follow-up, an excellent local control and cosmetic result were noted (D-F). No local steroid injections were administered after surgery and radiotherapy. HDR, high dose rate.

Figure 3 Image of a patient before (A) treatment of keloids excision and surface HDR brachytherapy. One week following surface HDR brachytherapy, mild radiation dermatitis was observed, characterized by temporary redness and changes in skin color (B). After 1 year (C) and 1.5 years (D) of follow-up, no recurrence and pains were noted. No local steroid injections were given after radiotherapy. HDR, high dose rate.

Table 4 presents the results of the GEE model. The parameter beta (β) in this context represents the average change in score with each passing month. A negative β value indicates a decrease in the score over time. This finding suggests a statistically significant decrease in all three scores as time progresses, as demonstrated in Figures 4-6. Specifically, Figure 4 shows the change in the VSS score. Figure 5 illustrates the VAS score changes, and Figure 6 displays the JSW score changes. All three figures reveal a clear downward trend in scores, indicating improvement in the scar severity, pain levels, and overall symptomatology over time, which supports the effectiveness of the brachytherapy treatment.

Figure 4 Changes in VSS score during the follow-up period. VSS, Vancouver Scar Scale.

Figure 5 Changes in VAS score during the follow-up period. VAS, Visual Analogue Scale.

Figure 6 Changes in JSW score during the follow-up period. JSW, Japan Scar Workshop.

There were no significant side effects except grade 1 acute radiation dermatitis. Some patients experienced temporary changes in skin color, ranging from redness to darkness, following RT. However, these changes resolved spontaneously within several weeks after treatment. No significant Grade 3 or higher acute or late side effects were observed during the follow-up period.

Discussion

Postoperative RT after keloid excision surgery is widely recognized as an effective adjuvant intervention with the aim of preventing keloid recurrence (7,8,14,15). Sequeira first described it in 1909 (6), and it is currently considered the most efficacious modality, according to recommendations from the International Advisory Panel on Scar Management (11). RT effectively addresses or mitigates keloids by inhibiting angiogenesis and, consequently, inflammation (25). The documented rates of therapeutic response typically range from 67% to 98% (25). It can be administered using orthovoltage X-ray, kilovoltage X-ray, electrons, or brachytherapy; however, there is no consensus on the optimal modality.

Introduced in 1903, brachytherapy offers distinct advantages over EBRT under certain circumstances, including a more targeted delivery of radiation to the specific area and reduced exposure of surrounding soft tissue to radiation (11,13). Recent systematic reviews and meta-analyses have shown that brachytherapy offers superior control rates in comparison to EBRT, particularly in postoperative management of keloids (13,15). A study by Mankowski et al. comparing recurrence rates between electron beam and brachytherapy found no significant difference (15). However, to date, no phase 3 clinical trials have directly compared the efficacy, advantages, and disadvantages of brachytherapy vs. electron beam therapy after keloid surgery. The combination of surgical excision and high-dose-rate (HDR) brachytherapy has been shown to markedly reduce recurrence rates, achieving a high patient satisfaction rate of 86.9% (16,26,29,30).

In addition to the favorable outcomes compared to EBRT, brachytherapy is particularly useful for keloid scars that have recurred following EBRT. When retreating, it is essential to consider the previous radiation dose, the volume of normal tissue treated, organs at risk, and the interval since previous radiation treatment. The risk of developing cancer in the irradiated area appears minimal, as no cases of brachytherapy-induced malignancy have been reported in the existing literature (11,26).

Study showed that both low dose rate (LDR) and HDR brachytherapy are effective and safe treatments for keloids (12). However, LDR brachytherapy, which requires patients to undergo treatment in a lead chamber for 20–72 hours, has been largely superseded by HDR brachytherapy due to issues with patient compliance and inconvenience. HDR brachytherapy, typically involving brief irradiation durations (under 10 minutes), is more suitable for outpatient settings.

The maximum biologically effective dose (BED) established for keloids is 30 Gy. Dosages exceeding this threshold do not confer additional efficacy benefits and may increase the risk of secondary carcinogenesis (16,25,26). Some studies have suggested increasing the dose per fraction, specifically recommending 20 Gy in 4 fractions, for regions such as the chest wall and shoulders, with an emphasis on the scapular and suprapubic areas (25). A recent study by Franzetti et al. (31) reviewed postoperative brachytherapy using a 3D treatment plan with a prescribed dose of 12 Gy in 4 fractions (3 Gy per fraction), administered twice daily with a 6-hour interval between fractions. Their study observed 36 recurrences (26.7%) and cumulative 12- and 36-month recurrence rates of 20.7% and 23.8%, respectively. In contrast, our study found no recurrences, likely due to the small sample size.

At our institution, we use 20 Gy in 4 fractions (approximately 30 Gy BED, with an α/β ratio of 10 Gy) for postoperative keloid RT. While adjuvant RT is traditionally administered within 24 hours of surgery to prevent fibroblast proliferation (32), a review by Lee et al. (33) and our own previous study (20) highlighted variability in the time interval between surgery and RT, with no significant impact on treatment outcomes. In fact, delayed RT (administered up to 2 weeks post-excision) showed comparable cosmesis and recurrence rates to immediate RT. In our study, a shorter time interval (less than 7 hours) for the initial dose after surgery demonstrated a lower recurrence rate compared to longer intervals (greater than 24 hours) (13). However, it is important to note that the quality of the evidence is limited by the variability in study designs. In our cohort, no recurrences were observed up to the cut-off date for outcome analysis, suggesting that a flexible time frame for initiating RT may still provide effective results. The optimal time interval remains a topic of ongoing debate.

The limitations of our study include its retrospective design, small sample size, and relatively short follow-up duration. Another limitation of this study is that, as keloids are a benign condition, patients often do not return for regular follow-up visits unless new lesions develop and require treatment. We also acknowledge the importance of considering potential confounding variables, such as genetic predisposition, comorbid conditions, and differences in pre-treatment interventions, in our study. Our medical records primarily document information related to the patients’ keloid status, including subjective complaints, objective scores, and family history of keloids. However, due to the limitations of the available data, we did not have access to detailed information on genetic predisposition of molecular analysis. Further long-term studies are needed to better assess the efficacy and safety of postoperative RT in keloids, and to account for the confounding factors to better understand their impact on keloid treatment outcomes.

To sum up, the indications for brachytherapy using surface moulds or flaps are similar to those for EBRT and may extend to situations requiring integrated or complex radiation fields. Brachytherapy is particularly suitable in cases involving steep-sloped and curved surfaces, as it allows for precision and homogeneity in irradiation while minimizing the inclusion of deeper structures in the radiation field, e.g., shoulder, jawline. Besides, for long wounds, it is noteworthy that at the senior author’s institution, brachytherapy is preferably employed over EBRT, with a defined cut-off point of 13 cm for the utilization of brachytherapy (11,25,26). The uncertainty of dose distribution at the junction of electron fields is no longer a problem using brachytherapy. In the decision-making process for adjuvant treatment of keloid patients, comprehensive consideration should be given to factors such as local control efficacy, cosmetic outcomes, potential toxicity, and the convenience or expected compliance associated with the chosen treatment approach.

In the decision-making process for adjuvant treatment of keloid patients, comprehensive consideration should be given to factors such as local control efficacy, cosmetic outcomes, potential toxicity, and the convenience or expected compliance associated with the chosen treatment approach.

Conclusions

In conclusion, brachytherapy is a viable, convenient, and safe modality for postoperative keloid treatment. Utilizing a dosage of 20 Gy administered in 4 fractions could yield excellent local control, and noteworthy, no grade 3 or higher toxicity is observed. Further prospective randomized trials to determine the long-term efficacy of postoperative brachytherapy for keloids are warranted.

Acknowledgments

We are grateful to Prof. Chung-Ying Lin and Ms. Wan-Ni Chen for providing the statistical consulting services from the Biostatistics Consulting Center, Clinical Medicine Research Center, National Cheng Kung University Hospital.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tro.amegroups.com/article/view/10.21037/tro-24-16/rc

Data Sharing Statement: Available at https://tro.amegroups.com/article/view/10.21037/tro-24-16/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tro.amegroups.com/article/view/10.21037/tro-24-16/coif). H.H.W.C. serves as an unpaid editorial board member of Therapeutic Radiology and Oncology from October 2024 to December 2026. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of NCKUH (No. B-ER-113-130) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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