22 Penis cancer

Penis cancer

11

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/07/2022

TABLE 3 EQD2 FOR VARIOUS HDR FRACTIONATION SCHEMES USING α/β-RATIO = 3GY FOR COMPLICATIONS AND 10 GY FOR TUMOUR. THE CALCULATED EQD2 IS ALSO SHOWN FOR THE 125% ISODOSE FOR VARIOUS PRESCRIPTIONS Prescription Dose (100%) 125% Isodose Dose per fraction (Gy) Total Dose (Gy) EQD2 (Gy) α/β-ratio = 3Gy EQD2 (Gy) α/β-ratio = 10Gy Total dose (Gy) EQD2 (Gy) α/β-ratio = 3Gy 3 (23) 42 50.4 45.5 52.5 63

3.12 (19)

38.4

47

42

48

58.8

3.3 (36)

39

49

43.2

48.8

61.5

3.9 (36)

35

48

40.5

43.8

60.4

4 (26)

36

50.4

42

45

63

4 (19)

40

56

46.7

50

70

TABLE 4 RECOMMENDATIONS FOR REPORTING HDR PENILE BRACHYTHERAPY INCLUDE:

GTV (cm 3 ) and CTV (cm 3 ) Number of needles and spacing Prescription total dose, number of fractions, fraction size

GTV D 98% , D 90% , V 125% , V 150% , V 200% CTV D 98% , D 90% , V 125% , V 150% , V 200% Urethra D 0.1cm 3 and D 0.2 cm 3 Skin D 0.1cm 3 and D 0.2 cm 3

HDR interstitial As this technique is still evolving, a range of doses have been reported (Table 2). Treatment fractions are given twice daily, 6 hours apart. Although very low volume residual disease can be treated with 38.4 Gy/12 fractions, the most commonly used prescription would be 42-45 Gy/12-14 fractions of 3.1-3.2 Gy per fraction (19). Table 2 shows reported fractionation schedules ranging from 3 Gy daily fractions, through 3-3.5 Gy and up to 4-4.3 Gy[23][24][25] [26]. Table 3 shows the corresponding EQD2. General consensus would suggest fraction sizes of 3-3.5 Gy and total dose depending on bulk of disease in the range of 38 Gy to 45 Gy (EQD2 42-45 Gy for α/β-ratio=10 Gy). Dose homogeneity is an important factor to reduce late sequelae, as are dose constraints to urethra and skin. Unfortunately, inconsistent reporting and limited experience have not allowed these to be clearly defined. We recommend reporting absolute volume of urethra receiving at least 115%of the prescribed dose(19)), and limiting urethral dose such that D 0.1cm 3 < 125% (~EQD2 60 Gy). In practice, confluent areas with dose of 125% at the skin surface should also be as limited as much as possible.

reference isodose according to the Paris system (20). Doses > 60 Gy correlated with stenoses, and doses > 65 Gy were associated with painful ulcerations. Complications were higher with larger treated volume (> 25 cm 3 ), more needle planes (>2) and higher dose rate (14). HDR surface mold The most frequently reported dose is 40 Gy/10 fractions delivered bid 6 hours apart over 5 days. Skin D 0.1cm 3 of 125% (50 Gy: EQD2 70 Gy) appears to be tolerated while skin D 0.1cm 3 105% (EQD2 58.8 Gy) was associated with more local failures. This may be a result of the lower surface dose being associated with less dose at a depth. The number of patients reported is very small and more data is required. All data is from HDR afterloading systems with an Ir-192 source.