Discussion

Treatment of ringworm consisted of quarantining infested children and applying various preparations, followed by tearing the hair. This treatment could last from several months to a few years without being very effective. ^{Reference Tilles, Cribier, Halioua, Revuz and Tilles7,Reference Cipollaro and Brodey8}

Radiation therapy has been a revolution and a standard in the treatment of ringworm. X-rays were an effective treatment for more than half a century, from 1904 until the 1960s. ^{Reference Tilles, Cribier, Halioua, Revuz and Tilles7} However, with the discovery of Griseofulvin, but above all, with the discovery of the formidable carcinogenic effects of ionising radiation, hair removal radiotherapy was completely abandoned. ^{Reference Rebollo, López-Barcenas and Arenas1}

Unfortunately, it is difficult to estimate the incidence of radiation-induced skin cancers of the scalp in Tunisia due to the absence of useful records. The patients were often treated with non-standardised machines and arbitrary doses were frequently delivered. ^{Reference Maalej, Frikha, Kochbati, Bouaouina, Sellami and Benna2} The various Tunisian publications concerned patients with scalp tumours in whom the history revealed a history of ringworm treated with radiotherapy. ^{Reference Maalej, Frikha, Kochbati, Bouaouina, Sellami and Benna2–Reference Fazaa, Cribier, Zaraa, Zermani, Maalej and Zouari4,Reference Mseddi, Bouassida, Marrekchi, Khemakhem, Gargouri and Turki9,Reference Frikha, Boudaya, Sellami, Bahloul, Mseddi and Turki10} Therefore, in our institute, it is customary to systematically look for a history of ringworm treated with radiotherapy and to consider the possibility of radiation-induced cancer.

The radiation-induced character is often easy to evoke in the presence of signs of radiodermatitis. In the absence of such lesions, the diagnosis can be retained in the presence of a history of radiotherapy, the occurrence of the tumour in the area of irradiation, and especially in the presence of multiple tumours. ^{Reference Zaraa, Ben Taazayet, Zribi, Chelly, El Euch and Trojjet11}

In our study, we report 137 patients with 200 radio-induced tumours of the scalp.

Radiation hair removal therapy has been undergone during childhood or adolescence with an average age of 8 years and extremes ranging from 5 to 12 years. The average age found in our work is comparable to that reported in other Tunisian series but slightly higher than that of foreign series (7·5 to 7·9 years). This difference could be explained by the earlier treatment of scalp ringworms in developed countries. ^{Reference Maalej, Frikha, Kochbati, Bouaouina, Sellami and Benna2,Reference Fazaa, Cribier, Zaraa, Zermani, Zeglaoui and Zouari3,Reference Shore, Moseson, Xue, Tse, Harley and Pasternack5,Reference Albert and Omran6,Reference Ron, Modan, Preston, Alfandary, Stovall and Boice John12,Reference Boaventura, Oliveira, Pereira, Soares and Teixeira-Gomes13}

We also observed a long latency period between hair removal radiotherapy and the onset of scalp lesions with an average of 42·6 years and extremes of 22 and 69 years. ^{Reference Shore, Moseson, Xue, Tse, Harley and Pasternack5–Reference Cipollaro and Brodey8} This is explained by the so-called stochastic or random effect of ionising radiation, to which is added a relatively long consultation period, which is itself attributable to the slow development of skin tumours, and in particular basel cell carcinoma (BCC), which is the most frequent.

In our study, the average consultation age was 56·5 years, with a peak frequency between 60 and 69 years. A Tunisian series by Zaraa et al. reported that the mean age was over 50 years and the peak frequency was between 60 and 70 years. ^{Reference Zaraa, Ben Taazayet, Zribi, Chelly, El Euch and Trojjet11} These results contrast with the results of the literature. In fact, the occurrence of radiation-induced skin tumours is reported at an earlier age, often less than 50 years, while sporadic tumours are described at an older age, often greater than 65 years. ^{Reference Shore, Moseson, Xue, Tse, Harley and Pasternack5,Reference Frikha, Boudaya, Sellami, Bahloul, Mseddi and Turki10,Reference Ron, Modan, Preston, Alfandary, Stovall and Boice John12}

This could be explained by the ageing of the cohort studied and the fact that most patients in Tunisia often consult late compared to other developed countries, due to a lack of awareness of the nature of the lesions and possible inaccessibility to health care services, especially in rural zones. It would have been more accurate to specify the age of the onset of the lesion. However, this parameter was not systematically included in the files and records consulted.

Our results are consistent with those of the Tunisian literature concerning the male predominance with a sex ratio of H/F of 3. ^{Reference Maalej, Frikha, Kochbati, Bouaouina, Sellami and Benna2,Reference Frikha, Boudaya, Sellami, Bahloul, Mseddi and Turki10,Reference Zaraa, Ben Taazayet, Zribi, Chelly, El Euch and Trojjet11} This is explained by the higher exposure to sunlight, which was most often occupational, and the higher rate of schooling among boys in the 1960s.

Clinically, the radiation-induced tumours reported in our series were in 73% of cases in the form of ulceration. In the literature, an often pigmented nodular appearance has been reported, which is specific to both primary and radio-induced BCCs. ^{Reference Fazaa, Cribier, Zaraa, Zermani, Maalej and Zouari4,Reference Zargari14}

All the authors agree that BCC is the predominant histological type for both radiation-induced skin tumours and primary skin tumours. ^{Reference Shore, Moseson, Xue, Tse, Harley and Pasternack5,Reference Mseddi, Bouassida, Marrekchi, Khemakhem, Gargouri and Turki9,Reference Ron, Modan, Preston, Alfandary, Stovall and Boice John12–Reference Zargari14} Our series nevertheless reported a good number of squamous cell carcinomas, that is, 25 lesions in 20 patients (12·5%). We have even reported cases of adnexal tumours. We also reported two cases of cutaneous lymphoma and one case of scalp melanoma.

Radiation-induced cancer of the scalp is treated with radiation therapy, surgery or a combination of the two. This decision is made on a case-by-case basis within a multidisciplinary consultation meeting.

The majority of studies have used surgery alone as a therapeutic modality. ^{Reference Fazaa, Cribier, Zaraa, Zermani, Maalej and Zouari4,Reference Sloane15–Reference Karagas, McDonald, Greenberg, Stukel, Weiss and Baron17}

In the series by Maalej et al., radiotherapy was the treatment of choice for 98 patients with radiation-induced scalp tumours. Radiotherapy was administered to 74 patients (75%). ^{Reference Maalej, Frikha, Kochbati, Bouaouina, Sellami and Benna2} Short et al. also reported a case with multiple radiation-induced BCC’s of the scalp treated by radiotherapy with satisfactory therapeutic and aesthetic results. ^{Reference Short, Calman, Ross and du Vivier18} In our series, radiotherapy was the modality of choice for the treatment of scalp lesions. About 77% of our patients had radiotherapy; it was post-operative in 29% of cases and exclusive in 48·9% of cases. The radiotherapy treatment in our study was well tolerated considering that the scalp had already been irradiated in the past. Indeed, no grade 4 radiodermatitis was observed.

Our study suffered from shortcomings in tracking. A majority of our patients were lost to follow-up at the end of treatment. Among the patients monitored, there were nine local recurrences which could be treated and six newly appearing basal cell carcinomas distant from the first tumour which could be operated on.

This risk of new basal cell carcinomas is classic for sporadic basal cell carcinomas and is increased for radio-induced BCCs. ^{Reference Zargari14,Reference Ekmekçi, Bostanci, Anadolu, Erdem and Gürgey19} Karagas et al. reported a relative risk (RR) equal to three for developing a new lesion in subjects irradiated for ringworm. ^{Reference Karagas, McDonald, Greenberg, Stukel, Weiss and Baron17} It therefore seems essential to us to stress to patients the importance of regular follow-up with careful clinical monitoring in order to diagnose any relapses in time and thus ensure the patient is receiving adequate treatment.