Advice pse on tumour size cut off point for SRS.

[Alison]

Hi,
I'm awaiting to hear about an apt for SRS with a linac (12 year old machine, may be Electa ) which looks like it'll be a couple of months away or 2013.  (I'm in the UK and there is a long waiting list to get on the machine).

My AN is 14.5mm (it said 14 on the MRI report I had in August, but both the neurosurgeon and radiologist said 14.5mm). My concern is that
I've heard from some other AN patients on a Uk forum, that Linac SRS machines, maybe only the old ones (?)  have a size limit of 20mm tumour size for treatment.

I always thought 3cm was the limit. Is this only for Gk or CK and not linac? I'm worried now cos if my tumour has grown before I get to have treatment it may be too big.

Does anyone know about this please?

Many thanks, Alison.

[mk]

Alison,

the size limits are very subjective. Generally for SRS the volume of the tumor counts, rather than the size in any given dimension. Also, the way sizes are reported can vary. I see in your signature that the size of your tumor is 14 mm x 10 x 8. This most likely means that the 14 mm measurement (which is the transverse measurement) includes the portion that is inside the IAC. Commonly in radiosurgery the spherical portion, inside the CPA is more important, because it contributes more to the volume. So the 20 mm limit may refer to the spherical portion of the tumor.
 In your case it is likely that this portion is less than 14 mm, and the other dimensions are very small. So without being a doctor, it seems to me that the tumor is quite small and growth shouldn't be a problem, given the slow rate of growth of these tumors. However it is best to mention these concerns to the radiation oncologist and get his/her opinion.

Marianna

[Alison]

Thanks Mariana,

that was helpful information. I asked about volume but the doc said they didn't measure it in volume. Don't know why, but I'm in the Uk and it seems we get less information from the docs than in the US, although I see you are in Canada. Sorry to see your AN grew after GK and you had surgery as well, but good to hear you don't have too many issues now.

I'll try to keep researching for more info.

Regards, Alison

[leapyrtwins]

Depends on the doc.

I don't know about SRS, but most docs have a limit of 3 cms for GK (gamma knife).  There are those who go beyond that though.

Jan

[mk]

Hi Alison,

Usually the reports don't mention volume. Your report mentions the other two dimensions. Based on this it is pretty easy to estimate the volume, assuming a spherical or oval shape (it is a simple math formula: pi*dimension1*dimension2*dimension3/6). But you need to know if the tumor extends in the CP angle, or if it is confined in the internal auditory canal. Does your report mention this information?
In the worse case scenario, where the 14 mm represents indeed the spherical portion of the tumor, the volume would be just 0.6 cc, which is still tiny (cut off for SRS usually being 10 cc).

Marianna

[Alison]

Thanks for the additional info Mariana.

My AN is in the IAC and bulging into the CPA, measurements 14.5cm x 10 x 8 on the MRI in August. (was originally told 14 on the report but radiologist said 14.5. Hope it included both IAC and CPA parts).

regards,

Alison.

[mattsmum]

hi - i believe 2.5 - 3.0cm are common upper limits. i had srs with linac and was told about 2.5cm. 14 or 14.5mm is not a significant difference in the measurement - and either way is well away from the upper limits so not likely to be an issue unless you were planning a long watch and wait period.
best wishes,
vikki