The Predictive Value of the Eighth Edition of the Clinical TNM Staging System for the Likelihood of Eye Salvage for Intraocular Retinoblastoma by Systemic Chemotherapy and Focal Therapy

Background: The American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) cTNM staging is emerging as a universal staging for all cancers, including retinoblastoma.

Methods: Here we evaluated the predictive value of the eighth edition AJCC/UICC cTNM staging in comparison with the International Intraocular Retinoblastoma Classification for eye globe salvage by primary systemic chemotherapy and focal therapy (CRD) using logistic regression model for the probability of treatment failure.

Results: The eye salvage rate for 565 treated eyes was 95% (n=139/147) for T1 tumors (98% for T1a and 93% for T1b), 56% (n=230/410) for T2 (81% for T2a and 53% for T2b), and 0% for T3 tumors, and was 98%, 93%, 76%, and 44% for group A, B, C, and D tumors, respectively. As estimated by odds ratios, T2 were 13.6-fold more likely to fail treatment than T1, and T1b, T2a, and T2b were 2.8-, 9.4-, and 35.1-fold more likely to fail treatment than T1a, respectively. Group B, C, and D tumors were 2.8-, 12.7-, and 50.1-fold more likely to fail treatment than group A tumors, respectively. Eye salvage rate was 62% for eyes with focal seeds (3 mm close to the tumor), and 42% for eyes with diffuse seeds (clouds more than 3 mm from tumor edge) (P<0.0001).

Conclusion: Both, the eighth edition cTNM classification and the International Intraocular Retinoblastoma Classification systems, can effectively predict eye salvage rates for retinoblastoma by CRD. Eyes with higher cT stages are more likely to experience treatment failure. Because the cT2b group is very heterogeneous, our findings suggest further division of this group based on the severity of vitreous/subretinal seeds, this should be revised in the next edition of cTNM system.