Use of Protoporphyrin Fluorescence to Determine Clinical Target Volumes for Nonmelanotic Skin Cancers Treated With Primary Radiation Therapy

Abstract

Purpose/Objective(s)This study prospectively investigated Protoporphyrin (PpIX) fluorescence as a means of determining the clinical target volume (CTV) necessary to encompass subclinical disease for non-melanotic skin cancers.Materials/MethodsPpIX photo-delineation was performed on 30 patients by applying δ-aminolevulinic acid (ALA) or Metvix™ (MAL) cream to the lesions to be treated, in order to delineate a CTV prior to treatment with radiation therapy. This CTV was then compared to conventional margins for subclinical disease (10 mm for poorly demarcated tumors).ResultsOf the 30 patients sampled, 26 (87%) of the lesions were BCCs and 4 (13%) were SCCs. 16/30 (53%) patients had primary nasal tumors. Seven (23%) patients had well-demarcated lesions and 23 (77%) patients had poorly demarcated tumors. The PpIX photo-delineation demonstrated a significant larger CTV - of 15 mm versus the conventional 10 mm expansion - for 16/23 (70%) cases of poorly demarcated lesions (p = 0.008), as well as for all BCCs (mean CTV with PpIX photo-delineation = 13 mm, p = 0.03) and for non-nasal lesions (mean CTV = 14 mm, p = 0.03). Nasal lesions had multifocal PpIX uptake in 15 of 16 cases (94%): the average expansion from PpIX fluorescence was 14 mm (variance = 122.9, p = 0.13), though this was not statistically significant. The local control rate after radiation therapy was 95.6% at 17.7 months.ConclusionsPpIX photo-delineation suggests that conventional 10 mm margins may be inadequately covering areas of subclinical disease in poorly demarcated skin tumors. PpIX photo-delineation also showed nasal lesions to be multifocal. Longer follow-up may be necessary to determine if this increase in CTV is clinically significant. Purpose/Objective(s)This study prospectively investigated Protoporphyrin (PpIX) fluorescence as a means of determining the clinical target volume (CTV) necessary to encompass subclinical disease for non-melanotic skin cancers. This study prospectively investigated Protoporphyrin (PpIX) fluorescence as a means of determining the clinical target volume (CTV) necessary to encompass subclinical disease for non-melanotic skin cancers. Materials/MethodsPpIX photo-delineation was performed on 30 patients by applying δ-aminolevulinic acid (ALA) or Metvix™ (MAL) cream to the lesions to be treated, in order to delineate a CTV prior to treatment with radiation therapy. This CTV was then compared to conventional margins for subclinical disease (10 mm for poorly demarcated tumors). PpIX photo-delineation was performed on 30 patients by applying δ-aminolevulinic acid (ALA) or Metvix™ (MAL) cream to the lesions to be treated, in order to delineate a CTV prior to treatment with radiation therapy. This CTV was then compared to conventional margins for subclinical disease (10 mm for poorly demarcated tumors). ResultsOf the 30 patients sampled, 26 (87%) of the lesions were BCCs and 4 (13%) were SCCs. 16/30 (53%) patients had primary nasal tumors. Seven (23%) patients had well-demarcated lesions and 23 (77%) patients had poorly demarcated tumors. The PpIX photo-delineation demonstrated a significant larger CTV - of 15 mm versus the conventional 10 mm expansion - for 16/23 (70%) cases of poorly demarcated lesions (p = 0.008), as well as for all BCCs (mean CTV with PpIX photo-delineation = 13 mm, p = 0.03) and for non-nasal lesions (mean CTV = 14 mm, p = 0.03). Nasal lesions had multifocal PpIX uptake in 15 of 16 cases (94%): the average expansion from PpIX fluorescence was 14 mm (variance = 122.9, p = 0.13), though this was not statistically significant. The local control rate after radiation therapy was 95.6% at 17.7 months. Of the 30 patients sampled, 26 (87%) of the lesions were BCCs and 4 (13%) were SCCs. 16/30 (53%) patients had primary nasal tumors. Seven (23%) patients had well-demarcated lesions and 23 (77%) patients had poorly demarcated tumors. The PpIX photo-delineation demonstrated a significant larger CTV - of 15 mm versus the conventional 10 mm expansion - for 16/23 (70%) cases of poorly demarcated lesions (p = 0.008), as well as for all BCCs (mean CTV with PpIX photo-delineation = 13 mm, p = 0.03) and for non-nasal lesions (mean CTV = 14 mm, p = 0.03). Nasal lesions had multifocal PpIX uptake in 15 of 16 cases (94%): the average expansion from PpIX fluorescence was 14 mm (variance = 122.9, p = 0.13), though this was not statistically significant. The local control rate after radiation therapy was 95.6% at 17.7 months. ConclusionsPpIX photo-delineation suggests that conventional 10 mm margins may be inadequately covering areas of subclinical disease in poorly demarcated skin tumors. PpIX photo-delineation also showed nasal lesions to be multifocal. Longer follow-up may be necessary to determine if this increase in CTV is clinically significant. PpIX photo-delineation suggests that conventional 10 mm margins may be inadequately covering areas of subclinical disease in poorly demarcated skin tumors. PpIX photo-delineation also showed nasal lesions to be multifocal. Longer follow-up may be necessary to determine if this increase in CTV is clinically significant.