Usefulness of fluorescence photography for diagnosis of oral cancer

Int. J. Oral Maxillojac. Surg. 1999; 28:206~10 Printed in Denmark . All rights reserved

Copyright 9 Munksgaard 1999 Intemational]oumcd of

Oral 8C Mcc~llofacialSurgery ISSN 0901-5027

Usefulness of fluorescence photography for diagnosis of oral cancer

K. Onizawa 1, H. Saginoya 2, Y. Furuya 1, H. Yoshida I , H. Fukuda 3 ~Department of Oral and Maxillofacial Surgery, Institute of Clinical Medicine, University of Tsukuba; 2photographic Section, University of Tsukuba Hospital, Tsukuba; 3Department of Dentistry and Oral and Maxillofacial Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan

Ir H. Saginoya, Y. Furuya, H. u H. Fukuda. Usefulness of fluorescence photography Jor diagnosis of oral cancer. Int. ,L Oral Maxillofac. Surg. 1999; 28." 206 210. 9 Munksgaard, 1999 Abstract. This study was carried out to evaluate the validity of fluorescence photograpl~y as an adjunctive diagnostic method for oral cancer. Fluorescence photography was performed on 130 oral lesions in 130 patients. Lesions showing red, orange or pink fluorescence on the photographs were defined as positive, while all other lesions were considered negative. Seventy-two (91.1%) of 79 carcinomas and 6 (85.7%) of 7 epithelial dysplasias were judged as positive, whereas two (4.5%) of 44 benign lesions that were not dysplasias showed positive fluorescence. Sixty-nine (94.5%) of 73 squamous cell carcinomas showed positive fluorescence. These results suggest that fluorescence photography is useful as an adjunctive diagnostic method for oral squamous cell carcinoma.

Early diagnosis of malignant neoplasms in the oral cavity is essential to achieve good results. Most malignant tumors of the oral cavity can be easily clinically diagnosed by inspection and palpation. Early differentiation between early stage cancers, precancerous lesions and benign lesions is often difficult because of the similar appearance of these lesions. Definitive diagnosis of malignant and benign lesions is commonly based on histological examination, but a non-invasive and simple screening test may be desirable as an adjunctive method. Vital staining with toluidine blue alone or in combination with Lugol's iodine3,12,14,22,23 and fluorescence imaging after administration of porphyrin-derived drugs 2,8J~ have been reported as approaches to discriminate between malignant and benign lesions. However, a relatively high frequency of false-positive results and skin photosen-

sitivity produced by fluorescent drugs have been indicated as drawbacks to vital staining3'14'2223 and fluorescence imagingS,10. The phenomenon of red autofluorescence of squamous cell carcinoma of the skin and oral cavity under Wood's light has been confirmed by several authors 5,18J9, since POLICARD 17 r e ported specific autofluorescence in experimental sarcoma under the same light as early as 1924. The red fluorescence was suggested to be associated with protoporphyrin produced by microorganisms dissolving host materials on an ulcerated tumor 6,7'j9, but its precise mechanism was not clarified. Recently, diagnostic methods using specific autofluorescence emitted by cancer tissue upon irradiation with laser or xenon light have been developed for oral mucous cancersl 1,13,24 Fluorescence photography appeared to be useful as an adjunctive diagnostic

Key words: fluorescence photography; autofluorescence; oral cancer. Accepted for publication 19 October 1998

method to differentiate oral cancer from benign lesions in a small clinical sample study 16'21. However, some authors have questioned the diagnostic value of autofluorescence because of occasional false-positive and false-negative findings9'18 and the lack of specificity. This study was carried out to evaluate the value of fluorescence photography as an adjunct in diagnosing oral cancer. Material and methods

Subjects consisted of 77 men and 53 women, ranging in age from 23 to 92 years with a mean age of 60 years, who had been referred for examination and treatment of oral lesions to the Division of Oral and Maxillofacial Surgery, University of Tsukuba Hospital, between 1987 and 1996. Fluorescence photographs were initially obtained and biopsies were then performed on the 130 lesions, irrespective of results of fluorescence photography.

Fluorescence photography Jor oral cancer

The fluorescence photography was performed using a Nikon F2 and specially designed instant photography cameras with ultraviolet flash lamps of 360 nm spectral peak 16'2z. Fujichrome 1600 Professional D film and Polaroid Instant Film type 339 were used in the Nikon F2 and instant photography cameras, respectively. To characterize the autofluorescence elicited, an SC-39 or SC-52 Fuji filter, in which fluorescence below 390 nm or 520 nm was absorbed, respectively, was set in front of the lens of the Nikon F2 camera. An SC-48 Fuji filter absorbing fluorescence below 480 nm was set in front of the instant photography camera. Ninety-four lesions were photographed with the Nikon F2 camera, 26 lesions with the instant photography camera and 10 lesions with both cameras. The autofluorescence of the lesions was judged according to the intensity of fluorescence depicted on the films. Lesions with red or pink fluorescence under the SC-39 filter, and those with red or orange fiuorescence under the SC-52 or -48 filter were defined as positive, whereas lesions without these colors of fluorescence were defined as negative. The autofluorescence emitted from lesions in the photographs was independently evaluated by three examiners who had not been informed of any definitive diagnosis. Final judgment was subject to agreement by two or more examiners.

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Table 1. Fluorescence diagnosis of carcinoma

Fluorescence DX Histological type

positive

negative

Total (%)

Squamous ceil Ca AdenoCa Other type

69 (94.5) 2 (100) 1 (25.0) ~'

4 (5.5) 0 3 (75.0) b

73 (100) 2 (100) 4 (100)

Total

72 (91.1)

7 (8.9)

79 (100)

DX: diagnosis; Ca: carcinoma; " undifferentiated Ca; b adenoid cystic Ca, acinic cell Ca and verrucous Ca.

Table 2. Fluorescence diagnosis of benign lesion

Fluorescence DX Histological DX

positive

negative

Total (%)

Dysplasia Hyperkeratosis Inflammatory ulcer Granulation tissue Benign tumor Others

6 (85.7) 0 0 1 (14.3) 0 1 (25.0) ~

l (14.3) 16 (100) 10 (i00) 7 (85.7) 6 (i00) 3 (75.0)

7 (100) 16 (100) 10 (100) 8 (100) 6 (100) 4 (100)

Total

8 (15.7)

43 (84.3)

51 (100)

DX: diagnosis; a inflamed nmcous cyst. If dysplasia is considered as a precancerous lesion, the positive rate would be 4.5% (2/44).

Table 3. Accuracy of fluorescence photography for oral cancer

Results Seventy-nine of the 130 lesions were histologically diagnosed as carcinoma and 51 lesions as benign. The carcinomas were classified as 73 squamous cell carcinomas, two adenocarcinomas, one adenoid cystic carcinoma, one acinic cell carcinoma, one undifferentiated carcinoma and one verrucous carcinoma. The benign lesions were histologically classified as 16 hyperkeratosis, ten inflammatory ulcerations, seven epithelial dysplasias, six benign tumors and twelve others. Based on the fluorescence photographs of the 130 lesions, the diagnosis of 126 lesions (96.9%) was agreed among all three examiners and of 4 lesions by two examiners. All ten lesions photographed by both N i k o n F2 and instant cameras elicited the same judgments in both photographic procedures. Eighty and 50 lesions were judged as having positive and negative fluorescence, respectively (Fig. 1). Seventy-two (91.1%) of 79 carcinomas showed positive fluorescence and they consisted of 69 squamous cell carcinomas, two adenocarcinomas and one undifferentiated carcinoma. The positive fluorescence rate was 94.5% for squamous cell carcinoma (Table 1). Sev-

Sensitivity Specificity Positive predictive value Negative predictive value Accuracy

Oral Cancer

(SCC+Dysplasia)

91.1 84.3 90.0 86.0 88.5

(93.8) (95.5) (97.4) (89.4) (94.4)

SCC: squamous cell carcinoma.

enty-three squamous cell carcinomas consisted of 5 T1, 40 T2, 9 T3 and 19 T4 cases (T classification of U1CC in 1987) and the four cases judged as negative were T2. Of 51 benign lesions, 8 (15.7%) were judged as positive and they consisted of six epithelial dysplasias, one inflamed granulation tissue and one mucous cyst. The positive fluorescence rates of epithelial dysplasia and other benign lesions were 85.7% and 4.5%, respectively (Table 2). Sensitivity, specificity and accuracy of fluorescence photography for oral cancer were 91.1%, 84.3% and 88.5%, respectively. When oral cancer was limited to squamous cell carcinoma and epithelial dysplasia was considered as a precancerous lesion and included, sensitivity, specificity and accuracy were 93.8%, 95.5% and 94.4%, respectively (Table 3).

Discussion Previous studies have reported that cutaneous or mucosal squamous cell carcinoma elicited red autofluorescence under Wood's light, and that the fluorescence disappeared with removal of the necrotic surface 5,9,~8. The autofluorescence of cancer tissue has also been reported to be reduced by irradiation a9' The current study showed that the autofluorescence of oral squamous cell carcinoma usually appeared reddish-pink under an SC-39 filter and reddish-orange under an SC-48 or -52 filter, and that other histological types of carcinonra showed similar autofluorescence. The autofluorescence was observed as a specific region in which debris adhered to the tumor surface, particularly in ulcerative and papillomatous white areas, but was not detected in regions where debris had been removed or in areas

908

O n i z a w a et al.

Fig. 1. Fluorescence photographs of lesion arising in tongue of a pa-

tient. A: Lesion histologically diagnosed as squamous cell carcinoma. B: Reddish-pink fluorescence elicited coincident with site of lesion, using SC-39 filter. C: Reddish-orange fluorescence elicited, using SC52 filter.

covered with an intact mucosa (Fig. 2). Repeated fluorescence photography revealed reduction and diminution of positive fluorescence associated with cancer regression due to irradiation or antitumor agents (Fig. 3). We previously reported in an experimental study 16 that the intensity and area of positive fluorescence increased with

Fig. 2. Same lesion as Fig. 1 after removal of fluorescent debris. A: debris located in center of lesion is removed. B & C: Reddish-pink or orange fluorescence disappears coincident with site of removed debris.

progression and enlargement of carcinoma. Accordingly, positive fluorescence was considered to follow progression and regression of malignant tumors. Several studies of h u m a n tumours and experimental animal tumors have suggested that the red fluorescence is mainly due to protoporphyrin pro-

duced by a variety of microorganisms which dissolve host materials on the ulcerated tumor surface 6,v. Others have suggested that a protoporphyrin precursor and blood constituents provided by host tissue were involved in producing fluorescence 7,19. It is also conceivable that blood constituents would be readily and frequently released from

Fluorescence photography for oral cancer

209

Fig. 3. Same lesion as in Fig. 1 after irradiation. A: Tumor covered with necrotic fur. B & C: Reddish-pink or orange fluorescence not detected on tumor surface.

host tissue invaded by cancer, because many blood capillaries are affected by angiogenesis factor 4. On the other hand, accumulation of porphyrin compounds has been suggested in fluorescent cancer tissue 24 and an increased accumulation of endogenous porphyrin compounds along with carcinogenesis has been demonstrated in experimental cancer tissue 1. Cultured cancer cells have also been reported to produce protoporphyrins in the presence of hemoglobin 15. Based on these studies and the findings of this study, the following mechanisms of autofluorescence in cancer may be considered. Autofluorescence localized in the debris of malignant ulcerations could be due to blood constituents released from host tissue to microorganisms or surface cancer cells, along with porphyrin precursors in necrotic cancer tissue, although the materials for porphyrins cannot permeate normal mucosa covering cancer tissue. The increase of autofluorescence associated with progression could be attributable to enlargement of the surface area

upon which the constituents are released and increased accumulation of necrotic tissue, whereas the decrease of autofluorescence with cancer regression could be due to reduction of the area and decrease of accumulation. Of the two benign lesions with positive fluorescence that were not dysplasias, the inflamed mucous cyst was caused by repeated biting, which explains the presence of blood constituents. The other lesion consisted of granulation tissue caused by a decayed tooth and the positive fluorescence might have been due to dental plaque adherent to the tooth. Both the dorsum of the tongue and dental plaque show autofluorescence, as described in previous reports Is4~ The dorsal surface of the tongue, containing filiform papillae, is not smooth and can easily retain materials producing porphyrin. Dental plaque may also contain blood constituents, since marginal periodontitis can readily give rise to gingival bleeding during eating or toothbrushing. Fluorescence in epithelial dysplasia might be

different from that of malignant ulcerative lesions because the frequent release of blood constituents to the surface is unlikely. As the color of fluorescence in epithelial dysplasia was similar to that of the dorsum of the tongue rather than to that of cancer tissue, this fluorescence may be due to retention of materials on the irregular surface. Accumulation of porphyrin compounds in dysplastic tissue, however, has been shown in experiments ~ and positive fluorescence in dysplasias could be in part dueto accumulated endogenous porphyrin compounds. The typical clinical appearance of a false-negative malignant neoplasm in the current study was an exophytic mass with a small area exposed to the oral cavity, or with a smooth surface having no ulceration. These negative results might be due to the lack of retention of accumulated fluorescent materials on the surface, whereby the density of fluorescent materials was too little to be detected. Several studies using laser spectroscopy to observe au-

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Onizawa et al.

tofluorescence have suggested a lower false-negative rate 11,13 a n d f u r t h e r refinement of the m e t h o d would be necessary to reduce the n u m b e r of falsenegative cases. Toluidine blue application has been well d o c u m e n t e d as a screening m e t h o d for oral malignancy. Meta-analysis of previous investigations of toluidine blue application revealed t h a t the sensitivity a n d specificity r a n g e d f r o m 97.8% to 93.5% a n d f r o m 92.9% to 73.3%, respectively 2~ This m e t h o d was highly sensitive a n d a special a p p a r a t u s was unnecessary for evaluation, but inflamed a n d ulcerated areas retained the dye a n d resulted in a relatively large n u m b e r of false-positive cases 3,22,23. A 14-day r e t u r n a p p o i n t m e n t with restaining was r e c o m m e n d e d to reduce false-positive cases 12. Fluorescence p h o t o g r a p h y is non-invasive, rapid, simple a n d reproducible. N o special knowledge or experience is needed to~ evaluate the findings, alt h o u g h some difficulty is involved in o b t a i n i n g clear pictures o f lesions located in or n e a r the root of the tongue or p h a r y n x . T h e results of this study suggest that the system is a useful adj u n c t to the diagnostic m e a n s for s q u a m o u s cell carcinoma, a l t h o u g h , ultimately, biopsies will be necessary.

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Address: Kojiro Onizawa Department of Oral and MaxilloJacial Surgery Institute of Clinical Medicine University of Tsukuba 1-1-1 Tennodai, Tsukuba-shi Ibaraki-ken 305-8575 Japan Tel: +81 298 53 3052 Fax." +81 298 53 3039 E-mail: k-oni@md, tsukuba, ac.jp